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on the great magnet the earth, by William Gilbert of Colchester
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Title: On the magnet, magnetick bodies also, and on the great magnet the earth
a new physiology, demonstrated by many arguments & experiments
Author: William Gilbert of Colchester
Release Date: September 26, 2010 [EBook #33810]
Language: English
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VVILLIAM GILBERT
OF COLCHESTER,
PHYSICIAN OF
LONDON.
ON THE MAGNET, MAGNETICK
BODIES ALSO, AND ON
the great magnet the earth; a new Physiology,
_demonstrated by many arguments_
& experiments.
[Illustration]
LONDON
* * * * *
IMPRINTED AT THE CHISWICK PRESS ANNO
MCM.
* * * * *
[Illustration]
* * * * *
{ij} [Illustration]
PREFACE TO THE CANDID
READER, STUDIOUS OF
THE MAGNETICK
PHILOSOPHY.
Clearer proofs, in the discovery of secrets, and in the investigation of
the hidden causes of things, being afforded by trustworthy experiments and
by demonstrated arguments, than by the probable guesses and opinions of the
ordinary professors of philosophy: so, therefore, that the noble substance
of that great magnet, our common mother (the earth), hitherto quite
unknown, and the conspicuous and exalted powers of this our globe, may be
the better understood, we have proposed to begin with the common magnetick,
stony, and iron material, and with magnetical bodies, and with the nearer
parts of the earth which we can reach with our hands and perceive with our
senses; then to proceed with demonstrable magnetick experiments; and so
penetrate, for the first time, into the innermost parts of the earth. For
after we had, in order finally to learn the true substance of the globe,
seen and thoroughly examined many of those things which have been obtained
from mountain heights or ocean depths, or from the profoundest caverns and
from hidden mines: we applied much prolonged labour on investigating the
magnetical forces; so wonderful indeed are they, compared with the forces
of all other minerals, surpassing even the virtues of all other bodies
about us. Nor have we found this our labour idle or unfruitful; since daily
during our experimenting, new and unexpected properties came to light; and
our Philosophy hath grown so much from the things diligently observed, that
we have attempted to expound the interior parts of the terrene globe, and
its native substance, upon magnetick principles; and to reveal to men the
earth (our common mother), and to point it out as if with the finger, by
real demonstrations and by experiments manifestly apparent to the senses.
And as geometry ascends from sundry very small and very easy principles to
the greatest and most difficult; by which the wit of man climbs above the
firmament: so our magnetical doctrine and science first sets forth in
convenient order the things which are less obscure; from these there come
to light others that are more remarkable; and at length in due order there
are opened the concealed and most secret things of the globe of the earth,
and the causes are made known of those things which, either through the
ignorance of the ancients or the neglect of moderns, have remained
unrecognized and overlooked. But why should I, in so vast an Ocean of Books
by which the minds of studious men are troubled and fatigued, through which
very foolish productions the world and unreasoning men are intoxicated, and
puffed up, rave and create literary broils, and while professing to be
philosophers, physicians, mathematicians and astrologers, neglect and
despise men of learning: why should I, I say, add aught further to this
so-perturbed republick of letters, and expose this noble philosophy, which
seems new and incredible by reason of so many things hitherto unrevealed,
to be damned and torn to pieces by the maledictions of those who are either
already sworn to the opinions of other men, or are foolish corruptors of
good arts, learned idiots, grammatists, sophists, wranglers, and perverse
little folk? But to you alone, true philosophizers, honest men, who seek
knowledge not from books only but from things themselves, have I addressed
these magnetical principles in this new sort of Philosophizing. But if any
see not fit to assent to these self-same opinions and paradoxes, let them
nevertheless mark the great array of experiments and discoveries (by which
notably every philosophy flourisheth), which have been wrought out and
demonstrated by us with many pains and vigils and expenses. In these
rejoice, and employ them to better uses, if ye shall be able. I know how
arduous it is to give freshness to old things, lustre to the antiquated,
light to the dark, grace to the despised, credibility to the doubtful; so
much the more by far is it difficult to win and establish some authority
for things new and unheard-of, in the face of all the opinions of all men.
Nor for that do we care, since philosophizing, as we deemed, is for the
few. To our own discoveries and experiments we have affixed asterisks,
larger and smaller, according to the importance and subtlety of the matter.
Whoso desireth to make trial of the same experiments, let him handle the
substances, not negligently and carelessly, but prudently, deftly, and in
the proper way; nor let him (when a thing doth not succeed) ignorantly
denounce our discoveries: for nothing hath been set down in these books
which hath not been explored and many times performed and repeated amongst
us. Many things in our reasonings and hypotheses will, perchance, at first
sight, seem rather hard, when they are foreign to the {iij} commonly
received opinion; yet I doubt not but that hereafter they will yet obtain
authority from the demonstrations themselves. Wherefore in magnetical
science, they who have made most progress, trust most in and profit most by
the hypotheses; nor will anything readily become certain to any one in a
magnetical philosophy in which all or at least most points are not
ascertained. This nature-knowledge is almost entirely new and unheard-of,
save what few matters a very few writers have handed down concerning
certain common magnetical powers. Wherefore we but seldom quote antient
Greek authors in our support, because neither by using greek arguments nor
greek words can the truth be demonstrated or elucidated either more
precisely or more significantly. For our doctrine magnetical is at variance
with most of their principles and dogmas. Nor have we brought to this work
any pretence of eloquence or adornments of words; but this only have we
done, that things difficult and unknown might be so handled by us, in such
a form of speech, and in such words as are needed to be clearly understood:
Sometimes therefore we use new and unusual words, not that by means of
foolish veils of vocabularies we should cover over the facts with shades
and mists (as Alchemists are wont to do) but that hidden things which have
no name, never having been hitherto perceived, may be plainly and correctly
enunciated. After describing our magnetical experiments and our information
of the homogenick parts of the earth, we proceed to the general nature of
the whole globe; wherein it is permitted us to philosophize freely and with
the same liberty which the Egyptians, Greeks, and Latins formerly used in
publishing their dogmas: whereof very many errors have been handed down in
turn to later authors: and in which smatterers still persist, and wander as
though in perpetual darkness. To those early forefathers of philosophy,
Aristotle, Theophrastus, Ptolemy, Hippocrates, and Galen, let due honour be
ever paid: for by them wisdom hath been diffused to posterity; but our age
hath detected and brought to light very many facts which they, were they
now alive, would gladly have accepted. Wherefore we also have not hesitated
to expound in demonstrable hypotheses those things which we have discovered
by long experience. Farewell.
* * * * *
TO THE MOST EMINENT AND LEARNED MAN
DR. WILLIAM GILBERT,
_a distinguished Doctor of Medicine amongst the_
Londoners, and Father of Magnetick Philosophy,
an Encomiastic Preface of Edward Wright
on the subject of these books
_Magnetical_.
_Should there by chance be any one, most eminent Sir, who reckons as of
small account these magnetical books and labours of yours, and thinks these
studies of yours of too little moment, and by no means worthy enough of the
attention of an eminent man devoted to the weightier study of Medicine:
truly he must deservedly be judged to be in no common degree void of
understanding. For that the use of the magnet is very important and wholly
admirable is better known for the most part to men of even the lowest class
than to need from me at this time any long address or commendation. Nor
truly in my judgment could you have chosen any topick either more noble or
more useful to the human race, upon which to exercise the strength of your
philosophic intellect; since indeed it has been brought about by the divine
agency of this stone, that continents of such vast circuit, such an
infinite number of lands, islands, peoples, and tribes, which have remained
unknown for so many ages, have now only a short time ago, almost within our
own memory, been quite easily discovered and quite frequently explored, and
that the circuit of the whole terrestrial globe also has been more than
once circumnavigated by our own countrymen, Drake and Cavendish; a fact
which I wish to mention to the lasting memory of these men. For by the
pointing of the iron touched by a loadstone, the points of South, North,
East, and West, and the other quarters of the world are made known to
navigators even under an overcast sky and in the darkest night; so that
thus they always very easily understand to which point of the world they
ought to direct their ship's course; which before the discovery of this
wonderful virtue of the magnetick [Greek: boreodeixis] was clearly
impossible. Hence in old times (as is established in histories), an
incredible anxiety and immense danger was continually threatening sailors;
for at the coming on of a tempest and the obscuring of the view of sun and
stars, they were left entirely in ignorance whither they were making; nor
could they find out this by any reasoning or skill. With what joy then may
we suppose them to have been filled, to what feelings of delight must all
shipmasters have given utterance, when that index magnetical first offered
itself to them as a most sure guide, and as it were a Mercury, for their
journey? But neither was this sufficient for this magnetical Mercury; to
indicate, namely, the right way, and to point, as it were, a finger in the
direction toward which the course must be {iiij} directed; it began also
long ago to show distinctly the distance of the place toward which it
points. For since the index magnetical does not always in every place look
toward the same point of the North, but deviates from it often, either
toward the East or toward the West, yet always has the same deviation in
the same place, whatever the place is, and steadily preserves it; it has
come about that from that deviation, which they call variation, carefully
noticed and observed in any maritime places, the same places could
afterwards also be found by navigators from the drawing near and approach
to the same variation as that of these same places, taken in conjunction
with the observation of the latitude. Thus the Portuguese in their voyages
to the East Indies had the most certain indications of their approach to
the Cape of Good Hope; as appears from the narrations of Hugo van
Lynschoten and of the very learned Richard Hakluyt, our countryman. Hence
also the experienced skippers of our own country, not a few of them, in
making the voyage from the Gulf of Mexico to the islands of the Azores,
recognized that they had come as near as possible to these same islands;
although from their sea-charts they seemed to be about six hundred British
miles from them. And so, by the help of this magnetick index, it would seem
as though that geographical problem of finding the longitude, which for so
many centuries has exercised the intellects of the most learned
Mathematicians, were going to be in some way satisfied; because if the
variation for any maritime place whatever were known, the same place could
very readily be found afterward, as often as was required, from the same
variation, the latitude of the same place being not unknown._
_It seems, however, that there has been some inconvenience and hindrance
connected with the observation of this variation; because it cannot be
observed excepting when the sun or the stars are shining. Accordingly this
magnetick Mercury of the sea goes on still further to bless all
shipmasters, being much to be preferred to Neptune himself, and to all the
sea-gods and goddesses; not only does it show the direction in a dark night
and in thick weather, but it also seems to exhibit the most certain
indications of the latitude. For an iron index, suspended on its axis (like
a pair of scales), with the most delicate workmanship so as to balance in
æquilibrio, and then touched and excited by a loadstone, dips to some fixed
and definite point beneath the horizon (in our latitude in London, for
example, to about the seventy-second degree), at which it at length comes
to rest. But under the æquator itself, from that admirable agreement and
congruency which, in almost all and singular magnetical experiments, exists
between the earth itself and a terrella (that is, a globular loadstone), it
seems exceedingly likely (to say the very least), and indeed more than
probable, that the same index (again stroked with a loadstone) will remain
in æquilibrio in an horizontal position. Whence it is evident that this
also is very probable, that in an exceedingly small progress from the South
toward the North (or contrariwise) there will be at least a sufficiently
perceptible change in that declination; so that from that declination in
any place being once carefully observed along with the latitude, the same
place and the same latitude may be very easily recognized afterward, even
in the darkest night and in the thickest mist by a declination instrument.
Wherefore to bring our oration at length back to you, most eminent and
learned Dr. Gilbert (whom I gladly recognize as my teacher in this
magnetick philosophy), if these books of yours on the Magnet had contained
nothing else, excepting only this finding of latitude from magnetick
declination, by you now first brought to light, our shipmasters, Britains,
French, Belgians, and Danes, trying to enter the British Channel or the
Straits of Gibraltar from the Atlantick Ocean in dark weather, would still
most deservedly judge them to be valued at no small sum of gold. But that
discovery of yours about the whole globe of the earth being magnetical,
although perchance it will seem to many "most paradoxical," producing even
a feeling of astonishment, has yet been so firmly defended by you at all
points and confirmed by so many experiments so apposite and appropriate to
the matter in hand, in Bk. 2, chap. 34; Bk. 3, chap. 4 and 12; and in
almost the whole of the fifth book, that no room is left for doubt or
contradiction. I come therefore to the cause of the magnetick variation,
which hitherto has distracted the minds of all the learned; for which no
mortal has ever adduced a more probable reason than that which has now been
set forth by you for the first time in these books of yours on the Magnet.
The [Greek: orthoboreodeixis] of the index magnetical in the middle of the
ocean, and in the middle of continents (or at least in the middle of their
stronger and more lofty parts), its inclining near the shore toward those
same parts, even by sea and by land, agreeing with the experiments Bk. 4,
chap. 2, on an actual terrella (made after the likeness of the terrestrial
globe, uneven, and rising up in certain parts, either weak or wanting in
firmness, or imperfect in some other way),--this inclination having been
proved, very certainly demonstrates the probability that that variation is
nought else than a certain deviation of the magnetick needle toward those
parts of the earth that are more vigorous and more prominent. Whence the
reason is readily established of that irregularity which is often perceived
in the magnetick variations, arising from the inæquality and irregularity
of those eminences and of the terrestrial forces. Nor of a surety have I
any doubt, that all those even who have either imagined or admitted points
attractive or points respective in the sky or the earth, and those who have
imagined magnetick mountains, or rocks, or poles, will immediately begin to
waver as soon as they have perused these books of yours on the Magnet, and
willingly will march with your opinion. Finally, as to the views which you
discuss in regard to the circular motion of the earth and of the
terrestrial poles, although to some perhaps they will seem most
supposititious, yet I do not see why they should not gain some favour, even
among the very men who do not recognize a sphærical motion of the earth;
since not even they can easily clear themselves from many difficulties,
which necessarily follow from the daily motion of the {v} whole sky. For in
the first place it is against reason that that should be effected by many
causes, which can be effected by fewer; and it is against reason that the
whole sky and all the sphæres (if there be any) of the stars, both of the
planets and the fixed stars, should be turned round for the sake of a daily
motion which can be explained by the mere daily rotation of the earth. Then
whether will it seem more probable, that the æquator of the terrestrial
globe in a single second (that is, in about the time in which any one
walking quickly will be able to advance only a single pace) can accomplish
a quarter of a British mile (of which sixty equal one degree of a great
circle on the earth), or that the æquator of the _primum mobile_ in the
same time should traverse five thousand miles with celerity ineffable; and
in the twinkling of an eye should fly through about five hundred British
miles, swifter than the wings of lightning, if indeed they maintain the
truth who especially assail the motion of the earth). Finally, will it be
more likely to allow some motion to this very tiny terrestrial globe; or to
build up with mad endeavour above the eighth of the fixed sphæres those
three huge sphæres, the ninth (I mean), the tenth, and the eleventh, marked
by not a single star, especially since it is plain from these books on the
magnet, from a comparison of the earth and the terrella, that a circular
motion is not so alien to the nature of the earth as is commonly supposed.
Nor do those things which are adduced from the sacred Scriptures seem to be
specially adverse to the doctrine of the mobility of the earth; nor does it
seem to have been the intention of Moses or of the Prophets to promulgate
any mathematical or physical niceties, but to adapt themselves to the
understanding of the common people and their manner of speech, just as
nurses are accustomed to adapt themselves to infants, and not to go into
every unnecessary detail. Thus in Gen. i. v. 16, and Psal. 136, the moon is
called a great light, because it appears so to us, though it it is agreed
nevertheless by those skilled in astronomy that many of the stars, both of
the fixed and wandering stars, are much greater. Therefore neither do I
think that any solid conclusion can be drawn against the earth's mobility
from Psal. 104, v. 5; although God is said to have laid the foundations of
the earth that it should not be removed for ever; for the earth will be
able to remain evermore in its own and self-same place, so as not to be
moved by any wandering motion, nor carried away from its seat (wherein it
was first placed by the Divine artificer). We, therefore, with devout mind
acknowledging and adoring the inscrutable wisdom of the triune Divinity
(having more diligently investigated and observed his admirable work in the
magnetical motions), induced by philosophical experiments and reasonings
not a few, do deem it to be probable enough that the earth, though resting
on its centre as on an immovable base and foundation, nevertheless is borne
around circularly._
_But passing over these matters (concerning which I believe no one has ever
demonstrated anything with greater certainty), without any doubt those
matters which you have discussed concerning the causes of the variation and
of the magnetick dip below the horizon, not to mention many other matters,
which it would take too long to speak of here, will gain very great favour
amongst all intelligent men, and especially (to speak after the manner of
the Chemists) amongst the sons of the magnetick doctrine. Nor indeed do I
doubt that when you have published these books of yours on the Magnet, you
will excite all the diligent and industrious shipmasters to take no less
care in observing the magnetick declination beneath the horizon than the
variation. Since (if not certain) it is at least probable, that the
latitude itself, or rather the effect of the latitude, can be found (even
in very dark weather) much more accurately from that declination alone,
than can either the longitude or the effect of the longitude from the
variation, though the sun itself is shining brightly or all the stars are
visible, with the most skilful employment likewise of all the most exact
instruments. Nor is there any doubt but that those most learned men, Peter
Plancius (not more deeply versed in Geography than in observations
magnetical), and Simon Stevinus, the most distinguished mathematician, will
rejoice in no moderate degree, when they first see these magnetical books
of yours, and observe their _[Greek: limeneuretikê]_, or _Haven-finding
Art_, enlarged and enriched by so great and unexpected an addition; and
without doubt they will urge all their own shipmasters (as far as they can)
to observe also everywhere the magnetick declination below the horizon no
less than the variation. May your Magnetical Philosophy, therefore, most
learned Dr. Gilbert, come forth into the light under the best auspices,
after being kept back not till the ninth year only (as Horace prescribes),
but already unto almost a second nine, a philosophy rescued at last by so
many toils, studyings, watchings, with so much ingenuity and at no moderate
expense maintained continuously through so many years, out of darkness and
dense mist of the idle and feeble philosophizers, by means of endless
experiments skilfully applied to it; yet without neglecting anything which
has been handed down in the writings of any of the ancients or of the
moderns, all which you did diligently peruse and perpend. Do not fear the
boldness or the prejudice of any supercilious and base philosophaster, who
by either enviously calumniating or stealthily arrogating to himself the
investigations of others seeks to snatch a most empty glory. Verily_
Envy detracts from great Homer's genius;
_but_
Whoever thou art, Zoilus, thou hast thy name from him.
_May your new physiology of the Magnet, I say (kept back for so many
years), come forth now at length into the view of all, and your Philosophy,
never to be enough admired, concerning the great Magnet (that is, the
earth); for, believe me_
(If there is any truth in the forebodings of seers),
_these books of yours on the Magnet will avail more for perpetuating the
memory of your name than the monument of any great Magnate placed upon your
tomb._
{vj}
* * * * *
_Interpretation of certain words.[1]_
Terrella, a globular loadstone.
Verticity, polar vigour, not [Greek: peridinêsis] but [Greek: peridineisios
dunamis]: not a vertex or [Greek: polos] but a turning tendency.
Electricks, things which attract in the same manner as amber.
Excited Magnetick, that which has acquired powers from the loadstone.
Magnetick Versorium, a piece of iron upon a pin, excited by a loadstone.
Non-magnetick Versorium, a versorium of any metal, serving for electrical
experiments.
Capped loadstone, which is furnished with an iron cap, or snout.
Meridionally, that is, along the projection of the meridian.
Paralleletically, that is, along the projection of a parallel.
Cusp, tip of a versorium excited by the loadstone.
Cross, sometimes used of the end that has not been touched and excited by a
loadstone, though in many instruments both ends are excited by the
appropriate termini of the stone.
Cork, that is, bark of the cork-oak.
Radius of the Orbe of the Loadstone, is a straight line drawn from the
summit of the orbe of the loadstone, by the shortest way, to the surface of
the body, which, continued, will pass through the centre of the loadstone.
Orbe of Virtue, is all that space through which the Virtue of any loadstone
extends.
Orbe of Coition, is all that space through which the smallest magnetick is
moved by the loadstone.
Proof, for a demonstration shown by means of a body.
Magnetick Coition: since in magnetick bodies, motion does not occur by an
attractive faculty, but by a concourse or concordance of both, not as if
there were an [Greek: helktikê dunamis] of one only, but a [Greek:
sundromê] of both; there is always a coition of the vigour: and even of the
body if its mass should not obstruct.
Declinatorium, a piece of Iron capable of turning about an axis, excited by
a loadstone, in a declination instrument.
* * * * *
INDEX OF CHAPTERS.
_Book 1._
Chap. 1. Ancient and modern writings on the Loadstone, with certain matters
of mention only, various opinions, & vanities.
Chap. 2. Magnet Stone, of what kind it is, and its discovery.
Chap. 3. The loadstone has parts distinct in their natural power, & poles
conspicuous for their property.
Chap. 4. Which pole of the stone is the Boreal: and how it is distinguished
from the austral.
Chap. 5. Loadstone seems to attract loadstone when in natural position: but
repels it when in a contrary one, and brings it back to order.
Chap. 6. Loadstone attracts the ore of iron, as well as iron proper,
smelted & wrought.
Chap. 7. What iron is, and of what substance, and its uses.
Chap. 8. In what countries and districts iron originates.
Chap. 9. Iron ore attracts iron ore.
Chap. 10. Iron ore has poles, and acquires them, and settles itself toward
the poles of the universe.
Chap. 11. Wrought iron, not excited by a loadstone, draws iron.
Chap. 12. A long piece of Iron (even though not excited by a loadstone)
settles itself toward North & South.
Chap. 13. Wrought iron has in itself certain parts Boreal & Austral: a
magnetick vigour, verticity, and determinate vertices or poles.
Chap. 14. Concerning other powers of loadstone, & its medicinal properties.
Chap. 15. The medicinal virtue of iron.
Chap. 16. That loadstone & iron ore are the same, but iron an extract from
both, as other metals are from their own ores; & that all magnetick
virtues, though weaker, exist in the ore itself & in smelted iron.
Chap. 17. That the globe of the earth is magnetick, & a magnet; & how in
our hands the magnet stone has all the primary forces of the earth, while
the earth by the same powers remains constant in a fixed direction in the
universe.
_Book 2._
Chap. 1. On Magnetick Motions.
Chap. 2. On the Magnetick Coition, and first on the attraction of Amber, or
more truly, on the attaching of bodies to Amber.
Chap. 3. Opinions of others on Magnetick Coition, which they call
Attraction.
Chap. 4. On Magnetick Force & Form, what it is; and on the cause of the
Coition.
Chap. 5. How the Power dwells in the Loadstone.
Chap. 6. How magnetick pieces of Iron and smaller loadstones conform
themselves to a terrella & to the earth itself, and by them are disposed.
Chap. 7. On the Potency of the Magnetick Virtue, and on its nature capable
of spreading out into an orbe.
Chap. 8. On the geography of the Earth, and of the Terrella.
Chap. 9. On the Æquinoctial Circle of the Earth and of a Terrella.
Chap. 10. Magnetick Meridians of the Earth.
Chap. 11. Parallels.
{vij} Chap. 12. The Magnetick Horizon.
Chap. 13. On the Axis and Magnetick Poles.
Chap. 14. Why at the Pole itself the Coition is stronger than in the other
parts intermediate between the æquator and the pole; and on the proportion
of forces of the coition in various parts of the earth and of the terrella.
Chap. 15. The Magnetick Virtue which is conceived in Iron is more apparent
in an iron rod than in a piece of Iron that is round, square, or of other
figure.
Chap. 16. Showing that Movements take place by the Magnetical Vigour though
solid bodies lie between; and on the interposition of iron plates.
Chap. 17. On the Iron Cap of a Loadstone, with which it is armed at the
pole (for the sake of the virtue), and on the efficacy of the same.
Chap. 18. An armed Loadstone does not indue an excited piece of Iron with
greater vigour than an unarmed.
Chap. 19. Union with an armed Loadstone is stronger; hence greater weights
are raised; but the coition is not stronger, but generally weaker.
Chap. 20. An armed Loadstone raises an armed Loadstone, which also attracts
a third; which likewise happens, though the virtue in the first be somewhat
small.
Chap. 21. If Paper or any other Medium be interposed, an armed loadstone
raises no more than an unarmed one.
Chap. 22. That an armed Loadstone draws Iron no more than an unarmed one:
and that an armed one is more strongly united to iron is shown by means of
an armed loadstone and a polished Cylinder of iron.
Chap. 23. The Magnetick Force causes motion toward unity, and binds firmly
together bodies which are united.
Chap. 24. A piece of Iron placed within the Orbe of a Loadstone hangs
suspended in the air, if on account of some impediment it cannot approach
it.
Chap. 25. Exaltation of the power of the magnet.
Chap. 26. Why there should appear to be a greater love between iron &
loadstone, than between loadstone & loadstone, or between iron & iron, when
close to the loadstone, within its orbe of virtue.
Chap. 27. The Centre of the Magnetick Virtues in the earth is the centre of
the earth; and in a terrella is the centre of the stone.
Chap. 28. A Loadstone attracts magneticks not only to a fixed point or
pole, but to every part of a terrella save the æquinoctial zone.
Chap. 29. On Variety of Strength due to Quantity or Mass.
Chap. 30. The Shape and Mass of the Iron are of most importance in cases of
coition.
Chap. 31. On long and round stones.
Chap. 32. Certain Problems and Magnetick Experiments about the Coition, and
Separation, and regular Motion of Bodies magnetical.
Chap. 33. On the Varying Ratio of Strength, and of the Motion of coition,
within the orbe of virtue.
Chap. 34. Why a Loadstone should be stronger in its poles in a different
ratio; as well in the Northern regions as in the Southern.
Chap. 35. On a Perpetual Motion Machine, mentioned by authors, by means of
the attraction of a loadstone.
Chap. 36. How a more robust Loadstone may be recognized.
Chap. 37. Use of a Loadstone as it affects iron.
Chap. 38. On Cases of Attraction in other Bodies.
Chap. 39. On Bodies which mutually repel one another.
_Book 3._
Chap. 1. On Direction.
Chap. 2. The Directive or Versorial Virtue (which we call verticity): what
it is, how it exists in the loadstone; and in what way it is acquired when
innate.
Chap. 3. How Iron acquires Verticity through a loadstone, and how that
verticity is lost and changed.
Chap. 4. Why Iron touched by a Loadstone acquires an opposite verticity,
and why iron touched by the true Northern side of a stone turns to the
North of the earth, by the true Southern side to the South; and does not
turn to the South when rubbed by the Northern point of the stone, and when
by the Southern to the North, as all who have written on the Loadstone have
falsely supposed.
Chap. 5. On the Touching of pieces of Iron of divers shapes.
Chap. 6. What seems an Opposing Motion in Magneticks is a proper motion
toward unity.
Chap. 7. A determined Verticity and a disponent Faculty are what arrange
magneticks, not a force, attracting them or pulling them together, nor
merely a strongish coition or unition.
Chap. 8. Of Discords between pieces of Iron upon the same pole of a
Loadstone, and how they can agree and stand joined together.
Chap. 9. Figures illustrating direction and showing varieties of rotations.
Chap. 10. On Mutation of Verticity and of Magnetick Properties, or on
alteration in the power excited by a loadstone.
Chap. 11. On the Rubbing of a piece of Iron on a Loadstone in places midway
between the poles, and upon the æquinoctial of a terrella.
Chap. 12. In what way Verticity exists in any Iron that has been smelted
though not excited by a loadstone.
Chap. 13. Why no other Body, excepting a magnetick, is imbued with
verticity by being rubbed on a loadstone, and why no body is able to instil
and excite that virtue, unless it be a magnetick.
Chap. 14. The Placing of a Loadstone above or below a magnetick body
suspended in æquilibrio changes neither the power nor the verticity of the
magnetick body.
Chap. 15. The Poles, Æquator, Centre in an entire Loadstone remain and
continue steady; by diminution and separation of some part they vary and
acquire other positions.
Chap. 16. If the Southern Portion of a Stone be lessened, something is also
taken away from the power of the Northern Portion.
Chap. 17. On the Use and Excellence of Versoria: and how iron versoria used
as pointers in sun-dials, and the fine needles of the mariners' compass,
are to be rubbed, that they may acquire stronger verticity.
{viij} _Book 4._
Chap. 1. On Variation.
Chap. 2. That the variation is caused by the inæquality of the projecting
parts of the earth.
Chap. 3. The variation in any one place is constant.
Chap. 4. The arc of variation is not changed equally in proportion to the
distance of places.
Chap. 5. An island in Ocean does not change the variation, as neither do
mines of loadstone.
Chap. 6. The variation and direction arise from the disponent power of the
earth, and from the natural magnetick tendency to rotation, not from
attraction, or from coition, or from other occult cause.
Chap. 7. Why the variation from that lateral cause is not greater than has
hitherto been observed, having been rarely seen to reach two points of
the mariners' compass, except near the pole.
Chap. 8. On the construction of the common mariners' compass, and on the
diversity of the compasses of different nations.
Chap. 9. Whether the terrestrial longitude can be found from the variation.
Chap. 10. Why in various places near the pole the variations are much more
ample than in a lower latitude.
Chap. 11. Cardan's error when he seeks the distance of the centre of the
earth from the centre of the cosmos by the motion of the stone of
Hercules; in his book 5, _On Proportions_.
Chap. 12. On the finding of the amount of variation: how great is the arc
of the Horizon from its arctick to its antarctick intersection of the
meridian, to the point respective of the magnetick needle.
Chap. 13. The observations of variation by seamen vary, for the most part,
and are uncertain: partly from error and inexperience, and the
imperfections of the instruments: and partly from the sea being seldom
so calm that the shadows or lights can remain quite steady on the
instruments.
Chap. 14. On the variation under the æquinoctial line, and near it.
Chap. 15. The variation of the magnetick needle in the great Æthiopick and
American sea, beyond the æquator.
Chap. 16. On the variation in Nova Zembla.
Chap. 17. Variation in the Pacifick Ocean.
Chap. 18. On the variation in the Mediterranean Sea.
Chap. 19. The variation in the interior of large Continents.
Chap. 20. Variation in the Eastern Ocean.
Chap. 21. How the deviation of the versorium is augmented and diminished
by reason of the distance of places.
_Book 5._
Chap. 1. On Declination.
Chap. 2. Diagram of declinations of the magnetick needle, when excited, in
the various positions of the sphere, and horizons of the earth, in which
there is no variation of the declination.
Chap. 3. An indicatory instrument, showing by the virtue of a stone the
degrees of declination from the horizon of each several latitude.
Chap. 4. Concerning the length of a versorium convenient for declination on
a terrella.
Chap. 5. That declination does not arise from the attraction of the
loadstone, but from a disposing and rotating influence.
Chap. 6. On the proportion of declination to latitude, and the cause of it.
Chap. 7. Explanation of the diagram of the rotation of a magnetick needle.
Chap. 8. Diagram of the rotation of a magnetick needle, indicating
magnetical declination in all latitudes, and from the rotation and
declination, the latitude itself.
Chap. 9. Demonstration of direction, or of variation from the true
direction, at the same time with declination, by means of only a single
motion in water, due to the disposing and rotating virtue.
Chap. 10. On the variation of the declination.
Chap. 11. On the essential magnetick activity sphærically effused.
Chap. 12. Magnetick force is animate, or imitates life; and in many things
surpasses human life, while this is bound up in the organick body.
_Book 6._
Chap. 1. On the globe of the earth, the great magnet.
Chap. 2. The Magnetick axis of the Earth persists invariable.
Chap. 3. On the magnetick diurnal revolution of the Earth's globe, as a
probable assertion against the time-honoured opinion of a Primum Mobile.
Chap. 4. That the Earth moves circularly.
Chap. 5. Arguments of those denying the Earth's motion, and their
confutation.
Chap. 6. On the cause of the definite time of an entire rotation of the
Earth.
Chap. 7. On the primary magnetick nature of the Earth, whereby its poles
are parted from the poles of the Ecliptick.
Chap. 8. On the Præcession of the Æquinoxes, from the magnetick motion of
the poles of the Earth, in the Arctick & Antarctick circle of the Zodiack.
Chap. 9. On the anomaly of the Præcession of the Æquinoxes, & of the
obliquity of the Zodiack.
[Illustration]
* * * * *
{1} [Illustration]
WILLIAM GILBERT
ON THE LOADSTONE, BK. I.
_CHAP. I._
ANCIENT AND MODERN WRITINGS
on the Loadstone, with certain matters of mention only,
_various opinions, & vanities_.
At an early period, while philosophy lay as yet rude and uncultivated in
the mists of error and ignorance, few were the virtues and properties of
things that were known and clearly perceived: there was a bristling forest
of plants and herbs, things metallick were hidden, and the knowledge of
stones was unheeded. But no sooner had the talents and toils of many
brought to light certain commodities necessary for the use and safety of
men, and handed them on to others (while at the same time reason and
experience had added a larger hope), than a thorough examination began to
be made of forests and fields, hills and heights; of seas too, and the
depths of the waters, of the bowels of the earth's body; and all things
began to be looked into. And at length by good luck the magnet-stone was
discovered in iron lodes, probably by smelters of iron or diggers of
metals. This, on being handled by metal folk, quickly displayed that
powerful and strong attraction for iron, a virtue not latent and obscure,
but easily proved by all, and highly praised and commended. And in after
time when it had emerged, as it were out of darkness and deep dungeons, and
had become dignified of men on account of its strong and amazing attraction
for iron, many philosophers as well as physicians of ancient days
discoursed of it, in short celebrated, as it were, its memory only; as for
instance Plato in the _Io_[2], Aristotle in the _De Anima_[3], in Book I.
only, Theophrastus the Lesbian, Dioscorides, C. Plinius Secundus, and
Julius Solinus[4]. As handed down by them the loadstone merely attracted
iron, the rest of its virtues were all undiscovered. But that the story of
the {2} loadstone might not appear too bare and too brief, to this singular
and sole known quality there were added certain figments and falsehoods,
which in the earliest times, no less than nowadays, used to be put forth by
raw smatterers and copyists to be swallowed of men. As for instance, that
if a loadstone be anointed with garlick, or if a diamond be near, it does
not attract iron[5]. Tales of this sort occur in Pliny, and in Ptolemy's
_Quadripartitum_; and the errors have been sedulously propagated, and have
gained ground (like ill weeds that grow apace) coming down even to our own
day, through the writings of a host of men, who, to fill put their volumes
to a proper bulk, write and copy out pages upon pages on this, that, and
the other subject, of which they knew almost nothing for certain of their
own experience. Such fables of the loadstone even Georgius Agricola
himself, most distinguished in letters, relying on the writings of others,
has embodied as actual history in his books _De Natura Fossilium_. Galen
noted its medicinal power in the ninth book of his _De Simplicium
Medicamentorum Facultatibus_, and its natural property of attracting iron
in the first book of _De Naturalibus Facultatibus_; but he failed to
recognize the cause, as Dioscorides before him, nor made further inquiry.
But his commentator Matthiolus repeats the story of the garlick and the
diamond, and moreover introduces Mahomet's shrine vaulted with
loadstones[6], and writes that, by the exhibition of this (with the iron
coffin hanging in the air) as a divine miracle, the public were imposed
upon. But this is known by travellers to be false. Yet Pliny relates that
Chinocrates the architect had commenced to roof over the temple of Arsinoe
at Alexandria with magnet-stone[7], that her statue of iron placed therein
might appear to hang in space. His own death, however, intervened, and also
that of Ptolemy, who had ordered it to be made in honour of his sister.
Very little was written by the ancients as to the causes of attraction of
iron; by Lucretius and others there are some short notices; others only
make slight and meagre mention of the attraction of iron: all of these are
censured by Cardan for being so careless and negligent in a matter of such
importance and in so wide a field of philosophizing; and for not supplying
an ampler notion of it and a more perfect philosophy: and yet, beyond
certain received opinions and ideas borrowed from others and ill-founded
conjectures, he has not himself any more than they delivered to posterity
in all his bulky works any contribution to the subject worthy of a
philosopher. Of modern writers some set forth its virtue in medicine only,
as [8]Antonius Musa Brasavolus, Baptista Montanus, Amatus Lusitanus, as
before them Oribasius in his thirteenth chapter _De Facultate
Metallicorum_, Aetius Amidenus, Avicenna, Serapio Mauritanus, Hali Abbas,
Santes de Ardoynis, Petrus Apponensis, Marcellus[9], Arnaldus. Bare mention
is made of certain points relating to the loadstone in very few words by
Marbodeus Callus, Albertus, {3} Matthæus Silvaticus, Hermolaus Barbarus,
Camillus Leonhardus, Cornelius Agrippa, Fallopius, Johannes Langius,
Cardinal Cusan, Hannibal Rosetius Calaber; by all of whom the subject is
treated very negligently, while they merely repeat other people's fictions
and ravings. Matthiolus compares the alluring powers of the loadstone which
pass through iron materials, with the mischief of the torpedo, whose venom
passes through bodies and spreads imperceptibly; Guilielmus Pateanus in his
_Ratio Purgantium Medicamentorum_ discusses the loadstone briefly and
learnedly. Thomas Erastus[10], knowing little of magnetical nature, finds
in the loadstone weak arguments against Paracelsus; Georgius Agricola, like
Encelius[11] and other metallurgists, merely states the facts; Alexander
Aphrodiseus in his _Problemata_ considers the question of the loadstone
inexplicable; Lucretius Carus, the poet of the Epicurean school, considers
that an attraction is brought about in this way: that as from all things
there is an efflux of very minute bodies, so from the iron atoms flow into
the space emptied by the elements of the loadstone, between the iron and
the loadstone, and that as soon as they have begun to stream towards the
loadstone, the iron follows, its corpuscles being entangled. To much the
same effect Johannes Costæus adduces a passage from Plutarch; Thomas
Aquinas[12], writing briefly on the loadstone in Chapter VII. of his
_Physica_, touches not amiss on its nature, and with his divine and clear
intellect would have published much more, had he been conversant with
magnetick experiments. Plato thinks the virtue divine. But when three or
four hundred years afterwards, the magnetick movement to North and South
was discovered or again recognized by men, many learned men attempted, each
according to the bent of his own mind, either by wonder and praise, or by
some sort of reasonings, to throw light upon a virtue so notable, and so
needful for the use of mankind. Of more modern authors a great number have
striven to show what is the cause of this direction and movement to North
and South, and to understand this great miracle of nature, and to disclose
it to others: but they have lost both their oil and their pains; for, not
being practised in the subjects of nature, and being misled by certain
false physical systems, they adopted as theirs, from books only, without
magnetical experiments, certain inferences based on vain opinions, and many
things that are not, dreaming old wives' tales. Marsilius Ficinus ruminates
over the ancient opinions, and in order to show the reason of the direction
seeks the cause in the heavenly constellation of the Bear, supposing the
virtue of the Bear to prevail in the stone and to be transferred to the
iron. Paracelsus asserted that there are stars, endowed with the power of
the loadstone, which attract to themselves iron. Levinus Lemnius describes
and praises the compass[13], and infers its antiquity on certain grounds;
he does not divulge the hidden miracle which he propounds. In the kingdom
{4} of Naples the Amalfians were the first (so it is said) to construct the
mariners' compass: and as Flavius Blondus says the Amalfians[14] boast, not
without reason, that they were taught by a certain citizen, Johannes Goia,
in the year thirteen hundred after the birth of Christ. That town is
situated in the kingdom of Naples not far from Salerno, near the promontory
of Minerva; and Charles V. bestowed that principality on Andrea Doria, that
great Admiral, on account of his signal naval services. Indeed it is plain
that no invention of man's device has ever done more for mankind than the
compass: some notwithstanding consider that it was discovered by others
previously and used in navigation, judging from ancient writings and
certain arguments and conjectures. The knowledge of the little mariners'
compass seems to have been brought into Italy by Paolo, the Venetian[15],
who learned the art of the compass in the Chinas about the year MCCLX.; yet
I do not wish the Amalfians to be deprived of an honour so great as that of
having first made the construction common in the Mediterranean Sea.
Goropius[16] attributes the discovery to the Cimbri or Teutons, forsooth
because the names of the thirty-two winds inscribed on the compass are
pronounced in the German tongue by all ship-masters, whether they be
French, British, or Spaniards; but the Italians describe them in their own
vernacular. Some think that Solomon, king of Judæa, was acquaint with the
use of the mariners' compass, and made it known to his ship-masters in the
long voyages when they brought back such a power of gold from the West
Indies: whence also, from the Hebrew word _Parvaim_[17], Arias Montanus
maintains that the gold-abounding regions of Peru are named But it is more
likely to have come from the coast of lower Æthiopia, from the region of
Cephala, as others relate. Yet that account seems to be less true, inasmuch
as the Phoenicians, on the frontier of Judæa, who were most skilled in
navigation in former ages (a people whose talents, work, and counsel
Solomon made use of in constructing ships and in the actual expeditions, as
well as in other operations), were ignorant of magnetick aid, the art of
the mariners' compass: For had it been in use amongst them, without doubt
the Greeks and also Italians and all barbarians would have understood a
thing so necessary and made famous by common use; nor could matters of much
repute, very easily known, and so highly requisite ever have perished in
oblivion; but either the learning would have been handed down to posterity,
or some memorial of it would be extant in writing. Sebastian Cabot was the
first to discover that the magnetick iron varied[18]. Gonzalus Oviedus[19]
is the first to write, as he does in the _Historia_, that in the south of
the Azores it does not vary. Fernelius in his book _De Abditis Rerum
Causis_ says that in the loadstone there is a hidden and abstruse cause,
elsewhere calling it celestial; and he brings forth nothing but the unknown
by means of what is still more unknown. {5} For clumsy, and meagre, and
pointless is his inquiry into hidden causes. The ingenious Fracastorio, a
distinguished philosopher, in seeking the reason for the direction of the
loadstone, feigns Hyperborean magnetick mountains attracting magnetical
things of iron: this view, which has found acceptance in part by others, is
followed by many authors and finds a place not in their writings only, but
in geographical tables, marine charts, and maps of the globe: dreaming, as
they do, of magnetick poles and huge rocks, different from the poles of the
earth. More than two hundred years earlier than Fracastorio there exists a
little work, fairly learned for the time, going under the name of one Peter
Peregrinus[20], which some consider to have originated from the views of
Roger Bacon, the Englishman of Oxford: In which book causes for magnetick
direction are sought from the poles of the heaven and from the heaven
itself. From this Peter Peregrinus, Johannes Taisnier of Hainault[21]
extracted materials for a little book, and published it as new. Cardan
talks much of the rising of the star in the tail of the Greater Bear, and
has attributed to its rising the cause of the variation: supposing that the
variation is always the same, from the rising of the star. But the
difference of the variation according to the change of position, and the
changes which occur in many places, and are even irregular in southern
regions, preclude the influence of one particular star at its northern
rising. The College of Coimbra[22] seeks the cause in some part of the
heaven near the pole: Scaliger in section CXXXI. of his _Exercitationes_ on
Cardan suggests a heavenly cause unknown to himself, and terrestrial
loadstones nowhere yet discovered. A cause not due to those sideritic
mountains named above, but to that power which fashioned them, namely that
portion of the heaven which overhangs that northern point. This view is
garnished with a wealth of words by that erudite man, and crowned with many
marginal subtilities; but with reasonings not so subtile. Martin Cortes[23]
considers that there is a place of attraction beyond the poles, which he
judges to be the moving heavens. One Bessardus[24], a Frenchman, with no
less folly notes the pole of the zodiack. Jacobus Severtius[25], of Paris,
while quoting a few points, fashions new errors as to loadstones of
different parts of the earth being different in direction: and also as to
there being eastern and western parts of the loadstone. Robert Norman[26],
an Englishman, fixes a point and region respective, not attractive; to
which the magnetical iron is collimated, but is not itself attracted.
Franciscus Maurolycus[27] treats of a few problems on the loadstone, taking
the trite views of others, and avers that the variation is due to a certain
magnetical island mentioned by Olaus Magnus[28]. Josephus Acosta[29],
though quite ignorant about the loadstone, nevertheless pours forth vapid
talk upon the loadstone. Livio Sanuto[30] in his Italian _Geographia_,
discusses at length the question whether the prime magnetick {6} meridian
and the magnetick poles are in the heavens or in the earth; also about an
instrument for finding the longitude: but through not understanding
magnetical nature, he raises nothing but errors and mists in that so
important notion. Fortunius Affaytatus[31] philosophizes foolishly enough
on the attraction of iron, and its turning to the poles. Most recently,
Baptista Porta[32], no ordinary philosopher, in his _Magia Naturalis_, has
made the seventh book a custodian and distributor of the marvels of the
loadstone; but little did he know or ever see of magnetick motions; and
some things that he noted of the powers which it manifested, either learned
by him from the Reverend Maestro Paolo, the Venetian[33], or evolved from
his own vigils, were not so well discovered or observed; but abound in
utterly false experiments, as will be clear in due place: still I deem him
worthy of high praise for having attempted so great a subject (as he has
done with sufficient success and no mean result in many other instances),
and for having given occasion for further research. All these
philosophizers of a previous age, philosophizing about attraction from a
few vague and untrustworthy experiments, drawing their arguments from the
hidden causes of things; and then, seeking for the causes of magnetick
directions in a quarter of the heavens, in the poles, the stars,
constellations, or in mountains, or rocks, space, atoms, attractive or
respective points beyond the heavens, and other such unproven paradoxes,
are whole horizons wrong, and wander about blindly. And as yet we have not
set ourselves to overthrow by argument those errors and impotent reasonings
of theirs, nor many other fables told about the loadstone, nor the
superstitions of impostors and fabulists: for instance, Franciscus
Rueus'[34] doubt whether the loadstone were not an imposture of evil
spirits: or that, placed underneath the head of an unconscious woman while
asleep, it drives her away from the bed if an adulteress: or that the
loadstone is of use to thieves by its fume and sheen, being a stone born,
as it were, to aid theft: or that it opens bars and locks, as Serapio[35]
crazily writes: or that iron held up by a loadstone, when placed in the
scales, added nothing to the weight of the loadstone, as though the gravity
of the iron were absorbed by the force of the stone: or that, as Serapio
and the Moors relate, in India there exist certain rocks of the sea
abounding in loadstone, which draw out all the nails of the ships which are
driven toward them, and so stop their sailing; which fable Olaus Magnus[36]
does not omit, saying that there are mountains in the north of such great
powers of attraction, that ships are built with wooden pegs, lest the iron
nails should be drawn from the timber as they passed by amongst the
magnetick crags. Nor this: that a white loadstone may be procured as a love
potion: or as Hali Abbas[37] thoughtlessly reports, that if held in the
hand it will cure gout and spasms: Or that it makes one acceptable and in
favour with princes, or eloquent, as Pictorio[38] has {7} sung; Or as
Albertus Magnus[39] teaches, that there are two kinds of loadstones, one
which points to the North, the other to the South: Or that iron is directed
toward the Northern stars by an influence imparted by the polar stars, even
as plants follow the sun, as Heliotrope does: Or that there is a
magnet-stone situated under the tail of the Greater Bear, as Lucas Gauricus
the Astrologer stated: He would even assign the loadstone, like the
Sardonyx and onyx, to the planet Saturn, yet at the same time he assigns it
with the adamant, Jasper, and Ruby, to Mars; so that it is ruled by two
planets. The loadstone moreover is said by him to pertain to the sign
Virgo; and he covers many such shameful pieces of folly with a veil of
mathematical erudition. Such as that an image of a bear is engraved on a
loadstone when the Moon faces towards the north, so that when hung by an
iron wire it may conciliate the influence of the celestial Bear, as
Gaudentius Merula[40] relates: Or that the loadstone drew iron and directed
it to the north, because it is superior in rank to iron, at the Bear, as
Ficinus writes, and Merula repeats: Or that by day it has a certain power
of attracting iron, but by night the power is feeble, or rather null: Or
that when weak and dulled the virtue is renewed by goats' blood, as
Ruellius[41] writes: Or that Goats' blood sets a loadstone free from the
venom of a diamond, so that the lost power is revived when bathed in goats'
blood by reason of the discord between that blood and the diamond: Or that
it removed sorcery from women, and put to flight demons, as Arnaldus de
Villanova dreams: Or that it has the power to reconcile husbands to their
wives, or to recall brides to their husbands, as Marbodeus Gallus[42],
chorus-leader of vanities, teaches: Or that in a loadstone pickled in the
salt of a sucking fish[43] there is power to pick up gold which has fallen
into the deepest wells, according to the narratives of Cælius Calcagninus.
With such idle tales and trumpery do plebeian philosophers delight
themselves and satiate readers greedy for hidden things, and unlearned
devourers of absurdities: But after the magnetick nature shall have been
disclosed by the discourse that is to follow, and perfected by our labours
and experiments, then will the hidden and abstruse causes of so great an
effect stand out, sure, proven, displayed and demonstrated; and at the same
time all darkness will disappear, and all error will be torn up by the
roots and will lie unheeded; and the foundations of a grand magnetick
philosophy which have been laid will appear anew, so that high intellects
may be no further mocked by idle opinions. Some learned men there are who
in the course of long voyages have observed the differences of magnetick
variation: the most scholarly Thomas Hariot[44], Robert Hues, Edward
Wright, Abraham Kendall, all Englishmen; Others there are who have invented
and produced magnetical instruments, and ready methods of observation,
indispensable for sailors and to those travelling afar: {8} as William
Borough[45] in his little book on the _Variation of the Compass_ or
Magneticall Needle, William Barlowe[46] in his _Supply_, Robert Norman in
his _Newe Attractive_. And this is that Robert Norman[47] (a skilful seaman
and ingenious artificer) who first discovered the declination of the
magnetick needle. Many others I omit wittingly; modern Frenchmen, Germans,
and Spaniards, who in books written for the most part in their native
tongues either misuse the placets of others, and send them forth furbished
with new titles and phrases as tricky traders do old wares with
meretricious ornaments; or offer something not worthy of mention even: and
these lay hands on some work filched from other authors and solicit some
one as their patron, or go hunting after renown for themselves among the
inexperienced and the young; who in all branches of learning are seen to
hand on errors and occasionally add something false of their own.
* * * * *
CHAP. II.
Magnet Stone, of what kind it is, and its
_discovery._
Loadstone, the stone which is commonly called the Magnet, derives its name
either from the discoverer (though he was not Pliny's fabulous
herdsman[48], quoted from Nicander, the nails of whose shoes and the tip of
whose staff stuck fast in a magnetick field while he pastured his flocks),
or from the region of Magnesia in Macedonia, rich in loadstones: Or else
from the city Magnesia in Ionia in Afia Minor, near the river Mæander.
Hence Lucretius says,
_The Magnet's name the observing Grecians drew_
_From the Magnetick region where it grew._
It is called Heraclean from the city Heraclea, or from the invincible
Hercules, on account of the great strength and domination and power which
there is in iron of subduing all things: it is also called _siderite_, as
being of iron; being not unknown to the most ancient writers, to the
Greeks, Hippocrates, and others, as also (I believe) to Jewish and Egyptian
writers; For in the oldest mines of iron, the most famous in Asia, the
loadstone was often dug out with its uterine brother, iron. And if the
tales be true which are told of the people of the Chinas, they were not
unacquainted in primitive times with magnetical experiments, for even
amongst {9} them the finest magnets of all are still found. The Egyptians,
as Manetho relates, gave it the name Os Ori: calling the power which
governs the turning of the sun Orus, as the Greeks call it Apollo. But
later by Euripides, as narrated by Plato, it was designated under the name
of Magnet. By Plato in the _Io_, Nicander of Colophon, Theophrastus,
Dioscorides, Pliny, Solinus, Ptolemy, Galen, and other investigators of
nature it was recognized and commended; such, however, is the variety of
magnets and their points of unlikeness in hardness, softness, heaviness,
lightness, density, firmness, and friability of substance: so great and
manifold are the differences in colour and other qualities, that they have
not handed down any adequate account of it, which therefore was laid aside
or left imperfect by reason of the unfavourable character of the time; for
in those times varieties of specimens and foreign products never before
seen were not brought from such distant regions by traders and mariners as
they have been lately, and now that all over the globe all kinds of
merchandise, stones, woods, spices, herbs, metals, and ore in abundance are
greedily sought after: neither was metallurgy so generally cultivated in a
former age. There is a difference in vigour; as whether it is male or
female: for it was thus that the ancients used often to distinguish many
individuals of the same species. Pliny quotes from Sotacus five kinds;
those from Æthiopia, Macedonia, Boeotia, the Troad, and Asia, which were
especially known to the ancients: but we have posited as many kinds of
loadstones as there are in the whole of nature regions of different kinds
of soil. For in all climates, in every province, on every soil, the
loadstone is either found, or else lies unknown on account of its rather
deep site and inaccesible position; or by reason of its weaker and less
obvious strength it is not recognized by us while we see and handle it. To
the ancients the differences were those of colour[49], how they are red and
black in Magnesia and Macedonia, in Boeotia red rather than black, in the
Troad black, without strength: While in Magnesia in Asia they are white,
not attracting iron, and resemble pumice-stone. A strong loadstone of the
kind celebrated so often nowadays in experiments presents the appearance of
unpolished iron, and is mostly found in iron mines: it is even wont to be
discovered in an unbroken lode by itself: Loadstones of this sort are
brought from East India, China, and Bengal, of the colour of iron, or of a
dark blood or liver colour; and these are the finest, and are sometimes of
great size, as though broken off a great rock, and of considerable weight;
sometimes single stones, as it were, and entire: some of these, though of
only one pound weight, can lift on high four ounces of iron or a half-pound
or even a whole pound. Red ones are found in Arabia, as broad as a tile,
not equal in weight to those brought from China, but strong and good: they
are a little darker in the island of Elba in the Tuscan sea, and together
with {10} these also grow white ones, like some in Spain in the mines of
Caravaca: but these are of lesser power. Black ones also are found, of
lower strength, such as those of the iron mines in Norway and in sea-coast
places near the strait of Denmark. Amongst the blue-black or dusky blue
also some are strong and highly commended. Other loadstones are of a leaden
colour, fissile and not-fissile, capable of being split like slates in
layers. I have also some like gray marble of an ashen colour, and some
speckled like gray marble, and these take the finest polish. In Germany
there are some perforated like honeycombs, lighter than any others, and yet
strong. Those are metallick which smelt into the best iron; others are not
easily smelted, but are burned up. There are loadstones that are very
heavy, as also others very light; some are very powerful in catching up
pieces of iron, while others are weaker and of less capacity, others so
feeble and barren that they with difficulty attract ever so tiny a piece of
iron and cannot repel an opposite magnetick. Others are firm and tough, and
do not readily yield to the artificer. Others are friable. Again, there are
some dense and hard as emery, or loose-textured and soft as pumice; porous
or solid; entire and uniform, or varied and corroded; now like iron for
hardness, yea, sometimes harder than iron to cut or to file; others are as
soft as clay. Not all magnets can be properly called stones; some rather
represent rocks; while others exist rather as metallick lodes; others as
clods and lumps of earth. Thus varied and unlike each other, they are all
endowed, some more, some less, with the peculiar virtue. For they vary
according to the nature of the soil, the different admixture of clods and
humours, having respect to the nature of the region and to their subsidence
in this last-formed crust of the earth, resulting from the confluence of
many causes, and the perpetual alternations of growth and decline, and the
mutations of bodies. Nor is this stone of such potency rare; and there is
no region wherein it is not to be found in some sort. But if men were to
search for it more diligently and at greater outlay, or were able, where
difficulties are present, to mine it, it would come to hand everywhere, as
we shall hereafter prove. In many countries have been found and opened
mines of efficacious loadstones unknown to the ancient writers, as for
instance in Germany, where none of them has ever asserted that loadstones
were mined. Yet since the time when, within the memory of our fathers,
metallurgy began to flourish there, loadstones strong and efficacious in
power have been dug out in numerous places; as in the Black Forest beyond
Helceburg; in Mount Misena not far from Schwartzenberg[50]; a fairly strong
kind between Schneeberg and Annaberg in Joachimsthal, as was noticed by
Cordus: also near the village of Pela in Franconia. In Bohemia it occurs in
iron mines in the Lessa district and other places, as Georgious Agricola
and several other men learned in metallurgy {11} witness. In like manner in
other countries in our time it is brought to light; for as the stone
remarkable for its virtues is now famous throughout the whole world, so
also everywhere every land produces it, and it is, so to speak, indigenous
in all lands. In East India, in China, in Bengal near the river Indus it is
common, and in certain maritime rocks: in Persia, Arabia, and the islands
of the Red Sea; in many places in Æthiopia, as was formerly Zimiri, of
which Pliny makes mention. In Asia Minor around Alexandria and the Troad;
in Macedonia, Boeotia, in Italy, the island of Elba, Barbary; in Spain
still in many mines as aforetime. In England quite lately a huge power of
it was discovered in a mine belonging to Adrian Gilbert, gentleman[51];
also in Devonshire and the Forest of Dean; in Ireland, too, Norway,
Denmark, Sweden, Lapland, Livonia, Prussia, Poland, Hungary. For although
the terrestrial globe, owing to the varied humours and natures of the soil
arising from the continual succession of growth and decay, is in the lapse
of time efflorescing through all its ambit deeper into its surface, and is
girt about with a varied and perishable covering, as it were with a veil;
yet out of her womb ariseth in many places an offspring nigher to the more
perfect body and makes its way to the light of day. But the weak and less
vigorous loadstones, enfeebled by the flow of humours, are visible in every
region, in every strath. It is easy to discover a vast quantity of them
everywhere without penetrating mountains or great depths, or encountering
the difficulties and hardships of miners; as we shall prove in the sequel.
And these we shall take pains so to prepare by an easy operation that their
languid and dormant virtue shall be made manifest. It is called by the
Greeks[52] [Greek: heraklios], as by Theophrastus, and [Greek: magnêtis];
and [Greek: magnês], as by Euripides, as quoted by Plato in the _Io_: by
Orpheus[53] too [Greek: magnêosa], and [Greek: sideritês] as though of
iron: by the Latins _magnes_, _Herculeus_; by the French _aimant_[54],
corruptly from _adamant_; by the Spaniards _piedramant_: by the Italians
_calamita_[55]; by the English LOADSTONE and ADAMANT STONE[56], by the
Germans _magness_[57] and _siegelstein_: Among English, French, and
Spaniards it has its common name from adamant; perhaps because they were at
one time misled by the name _sideritis_ being common to both: the magnet is
called [Greek: sideritês] from its virtue of attracting iron: the adamant
is called [Greek: sideritês] from the brilliancy of polished iron.
Aristotle designates it merely by the name of _the stone_:[58] [Greek:
Eoike de kai thalês ex hôn apomnêmoneuousi, kinêtikon ti tên psuchên
hupolabein, eiper ton lithon ephê psuchên echein, hoti ton sidêron kinei]:
_De Anima_, Lib. I. The name of magnet is also applied to another stone
differing from siderite, having the appearance of silver; it is like
Amianth in its nature; and since it consists of laminæ (like specular
stone)[59], it differs in form: in German _Katzensilber_ and _Talke_[60].
* * * * *
{12} CHAP. III.
The Loadstone has parts distinct in their natural
_power, & poles conspicuous for their property._
The stone itself manifests many qualities which, though known afore this,
yet, not having been well investigated, are to be briefly indicated in the
first place so that students may understand the powers of loadstone and
iron, and not be troubled at the outset through ignorance of reasonings and
proofs. In the heaven astronomers assign a pair of poles for each moving
sphere: so also do we find in the terrestrial globe natural poles
preeminent in virtue, being the points that remain constant in their
position in respect to the diurnal rotation, one tending to the Bears and
the seven stars; the other to the opposite quarter of the heaven. In like
manner the loadstone has its poles, by nature northern and southern, being
definite and determined points set in the stone, the primary boundaries of
motions and effects, the limits and governors of the many actions and
virtues. However, it must be understood that the strength of the stone does
not emanate from a mathematical point, but from the parts themselves, and
that while all those parts in the whole belong to the whole, the nearer
they are to the poles of the stone the stronger are the forces they acquire
and shed into other bodies: these poles are observant of the earth's poles,
move toward them, and wait upon them. Magnetick poles can be found in every
magnet, in the powerful and mighty (which Antiquity used to call the
masculine) as well as in the weak, feeble and feminine; whether its figure
is due to art or to chance, whether long, flat, square, three-cornered,
polished; whether rough, broken, or unpolished; always the loadstone
contains and shows its poles. * But since the spherical form, which is also
the most perfect, agrees best with the earth, being a globe, and is most
suitable for use and experiment, we accordingly wish our principal
demonstrations by the stone to be made with a globe-shaped magnet as being
more perfect and adapted for the purpose. Take, then, a powerful loadstone,
solid, of a just size, uniform, hard, without flaw[61]; make of it a globe
upon the turning tool used for rounding crystals and some other stones, or
with other tools as the material and firmness of the stone requires, for
sometimes it is difficult to be worked. The stone thus perpared is a true,
homogeneous offspring of the earth and of the same shape with it:
artificially possessed of the orbicular form which nature granted from the
beginning to the common mother earth: and it is a physical corpuscle imbued
with many virtues, by {13} means of which many abstruse and neglected
truths in philosophy buried in piteous darkness may more readily become
known to men. This round stone is called by us a [Greek: mikrogê] or
_Terrella_[62]. To find, then, the poles conformable to the earth's, take
the round stone in hand, and place upon the stone a needle or wire of iron:
the ends of the iron move upon their own centre and suddenly stand still.
Mark the stone with ochre or with chalk where the wire lies and sticks:
move the middle or centre of the wire to another place, and so on to a
third and a fourth, always marking on the stone along the length of the
iron where it remains at rest: those lines show the meridian circles, or
the circles like meridians on the stone, or terrella, all of which meet as
will be manifest at the poles of the stone. By the circles thus continued
the poles are made out, the Boreal as well as the southern, and in the
middle space betwixt these a great circle may be drawn for an æquator, just
as Astronomers describe them in the heavens and on their own globes, or as
Geographers do on the terrestrial globe: for that line so drawn on this our
terrella is of various uses in our demonstrations and experiments
magnetical. Poles are also found in a round stone by a versorium, a piece
of iron touched with a loadstone, and placed upon a needle or point firmly
fixed on a foot so as to turn freely about in the following way:[63]
[Illustration]
On the stone A B the versorium is placed in such a way that the versorium
may remain in equilibrium: you will mark with chalk the course of the iron
when at rest: Move the instrument to another spot, and again make note of
the direction and aspect: do the same thing in several places, and from the
concurrence of the lines of direction you will find one pole at the point
A, the other at B. A versorium placed near the stone also indicates the
true pole; when at right angles it eagerly beholds the stone and seeks the
pole itself directly, and is turned in a straight line through the axis to
the {14} centre of the stone. For instance, the versorium D faces toward A
and F, the pole and centre, whereas E does not exactly respect * either the
pole A or the centre F[64]. A bit of rather fine iron wire, of the length
of a barley-corn, is placed on the stone, and is moved over the regions and
surface of the stone, until it rises to the perpendicular[65]: for it
stands erect at the actual pole, whether Boreal or austral; the further
from the pole, the more it inclines from the vertical. The poles thus found
you shall mark with a sharp file or gimlet.
* * * * *
CHAP. IIII.
Which pole of the stone is the Boreal: & how it is
_distinguished from the austral_.
One pole of the earth turns toward the constellation of the Cynosure, and
constantly regards a fixed point in the heaven (except so far as it changes
by the fixed stars being shifted in longitude, which motion we recognize as
existing in the earth, as we shall hereafter prove): While the other pole
turns to the opposite face of heaven, unknown to the ancients, now visible
on long voyages, and adorned with multitudinous stars: In the same way the
loadstone has the property and power of directing itself North and South
(the earth herself consenting and contributing force thereto) according to
the conformation of nature, which arranges the movements of the stone
towards its native situation. Which thing is proved thus: Place a magnetick
stone (after finding the poles) in a round wooden vessel, a Bowl or dish,
at the same time place it together with the vessel (like a sailor in a
skiff) upon water in some large vessel or cistern, so that it may be able
to float freely in the middle, nor touch the edge of it, and where the air
is not disturbed by winds, which would thwart the natural movement of the
stone. Hereupon the stone placed as it were in a ship, in the middle of the
surface of the still and unruffled water, will at once put itself in motion
along with the vessel that carries it, and revolve circularly, until its
austral pole points to the north, and its boreal pole to the south. For it
reverts from the contrary position to the poles: and although by the first
too-vehement impulse it over-passes the poles; yet after returning again
and again, it rests at length at the poles, or at the meridian (unless
because of local reasons it is diverted some little from those points, or
from the meridional line, by some sort of variation[66], the cause of which
we will hereafter state). However often you move it away from its place, so
often by virtue of nature's noble dower does it seek again those sure and
{15} determined goals; and this is so, not only if the poles have been
disposed in the vessel evenly with the plane of the horizon, but also in
the case of one pole, whether austral or boreal, being raised in the vessel
ten, or twenty, or thirty, or fifty or eighty degrees, above * the plane of
the horizon, or lowered beneath it: Still you shall see the boreal part of
the stone seek the south, and the austral part seek the north; So much so
that if the pole of the stone shall be only one degree distant from the
Zenith and highest point of the heaven, in the case of a spherical stone,
the whole stone revolves until the pole occupies its own site; though not
in the absolutely direct line, it will yet tend toward those parts, and
come to rest in the meridian of the directive action. With a like impulse
too it is borne if the austral pole have been raised toward the upper
quarters, the same as if the Boreal had been exalted above the Horizon. But
it is always to be noted that, though there are various kinds of unlikeness
in the stones, and one loadstone may far surpass another in virtue and
efficiency; yet all hold to the same limits, and are borne toward the same
points. Further it is to be remembered * that all who before our time wrote
of the poles of the stone, and all the craftsmen and navigators, have been
very greatly in error in considering the part of the stone which tended to
the north as the north pole of the stone, and that which verged toward the
south, the south pole, which we shall hereafter prove to be false. So badly
hitherto hath the whole magnetick philosophy been cultivated, even as to
its foundation principles.
* * * * *
CHAP. V.
Loadstone seems to attract Loadstone when in natural
position: but repels it when in a contrary one, and brings
_it back to order_.
First of all we must declare, in familiar language, what are the apparent
and common virtues of the stone; afterward numerous subtilities, hitherto
abstruse and unknown, hidden in obscurity, are to be laid open, and the
causes of all these (by the unlocking of nature's secrets) made evident, in
their place, by fitting terms and devices. It is trite and commonplace that
loadstone draws iron; in the same way too does loadstone attract loadstone.
Place the stone which you have seen to have poles clearly distinguished,
and marked austral and boreal, in its vessel so as to float; and let the
poles be rightly arranged with respect to the plane of the horizon, or, at
any rate not much raised or awry: hold in your hand another stone the poles
of which are also known; in {16} such a way that its austral pole may be
toward the boreal pole of the one that is swimming, and near it, sideways:
for the floating stone forthwith follows the other stone (provided it be
within its force and dominion) and does not leave off nor forsake it until
it adhæres; unless by withdrawing your hand, you cautiously avoid contact.
In like manner if you set the boreal pole of the one you hold in your hand
opposite the austral pole of the swimming stone, they rush together and
follow each other in turn. For contrary poles allure contrary. If, however,
you apply in the same way the northern to the northern, and the austral to
the austral pole, the one stone puts the other to flight, and it turns
aside as though a pilot were pulling at the helm and it makes sail in the
opposite ward as one that ploughs the sea, and neither stands anywhere, nor
halts, if the other is in pursuit. For stone disposeth stone; the one turns
the other around, reduces it to range, and brings it back to harmony with
itself. When, however, they come together and are conjoined according to
the order of nature, they cohære firmly mutually. For instance, if you were
to set the boreal pole of that stone which is in your hand before the
tropic of Capricorn of a round floating loadstone (for it will be well to
mark out on the round stone, that is the terrella, the mathematical circles
as we do on a globe itself), or before any point between the æquator and
the austral pole; at once the swimming stone revolves, and so arranges
itself that its austral pole touches the other's boreal pole, and forms a
close union with it. In the same way, again, at the other side of the
æquator, with the opposite poles, you may produce similar results; and thus
by this art and subtilty we exhibit attraction, repulsion, and circular
motion for attaining a position of agreement and for declining hostile
encounters. Moreover 'tis in one and the same stone that we are thus able
to demonstrate all these things and also how the same part of one stone may
on division become either boreal or austral. Let A D be an oblong stone, in
which A is the northern, D the southern pole; cut this into two equal
parts, then set part A in its vessel on the water[67], so as to float.
[Illustration]
{17} And you will then see[68] that A the northern point will turn to the
south, as before; in like manner also the point D will move to the north,
in the divided stone, as in the whole one. Whereas, of the parts B and C,
which were before continuous, and are now divided, the one is southern B,
the other northern C. B draws C, desirous to be united, and to be brought
back into its pristine continuity: for these which are now two stones were
formed out of one: and for this cause C of the one turning itself to B of
the other, they mutually attract each other, and when freed from obstacles
and relieved of their own weight, as upon the surface of water, they run
together and are conjoined. But if you direct the part or point A to C in
the other stone, the one repels or turns away from the other: for so were
nature perverted, and the form of the stone perturbed, a form that strictly
keeps the laws which it imposed upon bodies: hence, when all is not rightly
ordered according to nature, comes the flight of one from the other's
perverse position and from the discord, for nature does not allow of an
unjust and inequitable peace, or compromise: but wages war and exerts force
to make bodies acquiesce well and justly. Rightly arranged, therefore,
these mutually attract each other; that is, both stones, the stronger as
well as the weaker, run together, and with their whole forces tend to
unity, a fact that is evident in all magnets, not in the Æthiopian only, as
Pliny supposed. The Æthiopian magnets if they be powerful, like those
brought from China, because all strong ones show the effect more quickly
and more plainly, attract more strongly in the parts nearest the pole, and
turn about until pole looks directly at pole. The pole of a stone more
persistently attracts and more rapidly seizes the corresponding part (which
they term the adverse part) of another stone; for instance, North pulls
South; just so it also summons iron with more vehemence, and the iron
cleaves to it more firmly whether it have been previously excited by the
magnet, or is untouched. For thus, not without reason hath it been ordained
by nature, that the parts nearer to the pole should more firmly attract:
but that at the pole itself should be the seat, the throne, as it were, of
a consummate and splendid virtue, to which magnetical bodies on being
brought are more vehemently attracted, and from which they are with utmost
difficulty dislodged. So the poles are the parts which more particularly
spurn and thrust away things strange and alien perversely set beside them.
* * * * *
{18} CHAP. VI.
Loadstone attracts the ore of iron, as well as iron
_proper, smelted and wrought_.
Principal and manifest among the virtues of the * magnet, so much and so
anciently commended, is the attraction of iron; for Plato states that the
magnet, so named by Euripides, allures iron, and that it not only draws
iron rings but also indues the rings with power to do the same as the
stone; to wit, draw other rings, so that sometimes a long chain of iron
objects, nails or rings is formed, some hanging from others. The best iron
(like that which is called _acies_ from its use, or _chalybs_ from the
country of the Chalybes) is best and strongly drawn by a powerful
loadstone; whereas the less good sort, which is impure, rusty, and not
thoroughly purged from dross, and not wrought in second furnaces, is more
feebly drawn; and yet more weakly when covered and defiled with thick,
greasy, and sluggish humours. It also draws ores of iron, those that are
rich and of iron colour; the poorer and not so productive ores it does not
attract, except they be prepared with some art. A loadstone loses some
attractive virtue, and, as it were, pines away with age, if exposed too
long to the open air instead of being laid in a case with filings or scales
of iron. Whence it should be buried in such materials; for there is nothing
that plainly resists this exhaustless virtue which does not destroy the
form of the body, or corrode it; not even if a thousand adamants were
conjoined. Nor do I consider that there is any such thing as the
Theamedes[69], or that it has a power opposite to that of the loadstone.
Although Pliny, that eminent man and prince of compilers (for it is what
others had seen and discovered, not always or mainly his own observations,
that he has handed down to posterity) has copied from others the fable now
made familiar by repetition: That in India there are two mountains near the
river Indus; the nature of one being to hold fast all that is iron, for it
consists of loadstone; the other's nature being to repel it, for it
consists of the Theamedes. Thus if one had iron nails in one's boots, one
could not tear away one's foot on the one mountain, nor stand still on the
other. Albertus Magnus writes that a loadstone had been found in his day
which with one part drew to itself iron, and repelled it with its other
end; but Albertus observed the facts badly; for every loadstone attracts
with one end iron that has been touched with a loadstone, and drives it
away with the other; and draws iron that been touched with a loadstone more
powerfully than iron that has not been so touched.
* * * * *
{19} CHAP. VII.
What Iron is, and of what substance,
_and its uses._
For that now we have declared the origin and nature of the loadstone, we
think it necessary first to add a history of iron and to indicate the
hitherto unknown forces of iron, before this our discourse goes on to the
explanation of magnetick difficulties and demonstrations, and to deal with
the coitions and harmonies of loadstone with iron. Iron is by all reckoned
in the class of metals, and is a metal livid in colour, very hard, glows
red-hot before it melts, being most difficult of fusion, is beaten out
under the hammer, and is very resonant. Chemists say that if a bed of fixed
earthy sulphur be combined with fixed earthy quicksilver, and the two
together are neither pure white but of a livid whiteness, if the sulphur
prevail, iron is formed. For these stern masters of metals who by many
inventions twisting them about, pound, calcine, dissolve, sublime, and
precipitate, decide that this metal, both on account of the earthy sulphur
and of the earthy mercury, is more truly a son of the earth than any other;
they do not even think gold or silver, lead, tin, or copper itself so
earthy; for that reason it is not smelted except in the hottest furnaces,
with bellows; and when thus fused, on having again grown hard it is not
melted again without heavy labour; but its slag with the utmost difficulty.
It is the hardest of metals, subduing and breaking all things, by reason of
the strong concretion of the more earthy matter. Wherefore we shall better
understand what iron is, when we shall declare what are the causes and
substance of metals, in a different way from those who before our time have
considered them. Aristotle takes the material of the metals to be vapour.
The chemists in chorus pronounce their actual elements to be sulphur and
quicksilver. Gilgil Mauritanus gives it as ashes moistened with water.
Georgius Agricola makes it out to be water and earth mixed; nor, to be
sure, is there any difference between his opinion and the position taken by
Mauritanus. But ours is that metals arise and effloresce at the summits of
the earth's globe, being distinguished each by its own form, like some of
the other substances dug out of it, and all bodies around us. The earth's
globe does not consist of ashes or inert dust. Nor is fresh water an
element, but a more simple consistency of evaporated fluids of the earth.
Unctuous bodies, fresh water devoid of properties, quicksilver and sulphur,
none of these are principia of metals: these latter, {20} things are the
results of a different nature, they are neither constant nor antecedent in
the course of the generation of metals. The earth emits various humours,
not begotten of water nor of dry earth, nor from mixtures of these, but
from the substance of the earth itself: these humours are not distinguished
by contrary qualities or substance, nor is the earth a simple substance, as
the Peripateticks dream. The humours proceed from vapours sublimated from
great depths; all waters are extracts and, as it were, exudations from the
earth. Rightly then in some measure does Aristotle make out the matter of
metals to be that exhalation which in continuance thickens in the lodes of
certain soils: for the vapours are condensed in places which are less hot
than the spot whence they issued, and by help of the nature of the soils
and mountains, as in a womb, they are at fitting seasons congealed and
changed into metals: but it is not they alone which form ores, but they
flow into and enter a more solid material, and so form metals. So when this
concreted matter has settled down in more temperate beds, it begins to take
shape in those tepid places, just as seed in the warm womb, or as the
embryo acquires growth: sometimes the vapour conjoins with suitable matter
alone: hence some metals are occasionally though rarely dug up native, and
come into existence perfect without smelting: but other vapours which are
mixed with alien soils require smelting in the way that the ores of all
metals are treated, which are rid of all their dross by the force of fires,
and being fused flow out metallick, and are separated from earthy
impurities but not from the true substance of the earth. But in so far as
that it becomes gold, or silver, or copper, or any other of the existing
metals, this does not happen from the quantity or proportion of material,
nor from any forces of matter, as the Chemists fondly imagine; but when the
beds and region concur fitly with the material, the metals assume forms
from the universal nature by which they are perfected; in the same manner
as all the other minerals, plants, and animals whatever: otherwise the
species of metals would be vague and undefined, which are even now turned
up in such scanty numbers that scarce ten kinds are known. Why, however,
nature has been so stingy as regards the number of metals, or why there
should be as many as are known to man, it is not easy to explain; though
the simple-minded and raving Astrologers refer the metals each to its own
planet. But there is no agreement of the metals with the planets, nor of
the planets with the metals, either in numbers or in properties. For what
connexion is there of iron with Mars? unless it be that from the former
numerous instruments, particularly swords and engines of war, are
fashioned. What has copper to do with Venus? or how does tin, or how does
spelter correspond with Jupiter? They should rather be dedicated to Venus.
But this is old wives' talk. Vapour is then a remote cause in the
generation of the metals; the fluid condensed from {21} vapours is a more
proximate one, like the blood and semen in the generation of animals. But
those vapours and juices from vapours pass for the most part into bodies
and change them into marcasites and are carried into lodes (for we have
numerous cases of wood so transmuted), the fitting matrices of bodies,
where they are formed as metals. They enter most often into the truer and
more homogeneal substance of the globe, and in the process of time a vein
of iron results; loadstone is also produced, which is nought else than a
noble kind of iron ore: and for this reason, and on account of its
substance being singular, alien from all other metals, nature very rarely,
if ever, mixes with iron any other metal, while the other metals are very
often minutely mixed, and are produced together. Now when that vapour or
those juices happen to meet, in fitting matrices, with efflorescences
deformed from the earth's homogenic substance, and with divers precipitates
(the forms working thereto), the remainder of the metals are generated (a
specifick nature affecting the properties in that place). For the hidden
primordial elements of metals and stones lie concealed in the earth, as
those of herbs and plants do in its outer crust. For the soil dug out of a
deep well, where would seem to be no suspicion of a conception of seed,
when placed on a very high tower, produces, by the incubation of sun and
sky, green herbage and unbidden weeds; and those of the kind which grow
spontaneously in that region, for each region produces its own herbs and
plants, also its own metals.
_[70]Here corn exults, and there the grape is glad,_
_Here trees and grass unbidden verdure add._
_So mark how Tmolus yields his saffrone store,_
_But ivory is the gift of Indian shore;_
_With incense soft the softer Shebans deal;_
_The stark Chalybeans' element is steel:_
_With acrid castor reek the Pontic wares,_
_Epirus wins the palm of Elian mares._
But what the Chemists (as Geber, and others) call fixed earthy sulphur in
iron is nothing else than the homogenic earth-substance concreted by its
own humour, amalgamated with a double fluid: a metallick humour is inserted
along with a small quantity of the substance of the earth not devoid of
humour. Wherefore the common saying that in gold there is pure earth, but
in iron mostly impure, is wrong; as though there were indeed such a thing
as natural earth, and that the globe itself were (by some unknown process
of refining) depurate. In iron, especially in the best iron, there is earth
in its own nature true and genuine; in the other metals there is not so
much earth as that in place of earth and precipitates there are
consolidated and (so to speak) fixed salts, which are efflorescences of the
globe, and which differ also greatly {22} in firmness and consistency: In
the mines their force rises up along with a twofold humour from the
exhalations, they solidify in the underground spaces into metallic veins:
so too they are also connate by virtue of their place and of the
surrounding bodies, in natural matrices, and take on their specific forms.
Of the various constitutions of loadstones and their diverse substances,
colours, and virtues, mention has been made before: but, now having stated
the cause and origin of metals, we have to examine ferruginous matter not
as it is in the smelted metal, but as that from which the metal is refined.
Quasi-pure iron is found of its proper colour and in its own lodes; still,
not as it will presently be, nor as adapted for its various uses. It is
sometimes dug up covered with white silex or with other stones. It is often
the same in river sand, as in Noricum. A nearly pure ore of iron is now
often dug up in Ireland, which the smiths, without the labours of furnaces,
hammer out in the smithy into iron implements. In France iron is very
commonly smelted out of a liver-coloured stone, in which are glittering
scales; the same kind[71] without the scales is found in England, which
also they use for craftsmen's ruddle[72]. In Sussex in England[73] is a
rich dusky ore and also one of a pale ashen hue, both of which on being
dried for a time, or kept in moderate fires, presently acquire a
liver-colour; here also is found a dusky ore square-shaped with a black
rind of greater hardness. An ore having the appearance of liver is often
variously intermingled with other stones: as also with the perfect
loadstone which yields the best of iron. There is also a rusty ore of iron,
one of a leaden hue tending to black, one quite black, or black mixed with
true cobalt: there is another sort mixed either with pyrites, or with
sterile plumbago. One kind is also like jet, another like bloodstone. The
emery used by armourers, and by glaziers for glass-cutting, called amongst
the English Emerelstone, by the Germans Smeargel, is ferruginous; albeit
iron is extracted from it with difficulty, yet it attracts the versorium.
It is now and then found in deep iron and silver diggings. Thomas Erastus
says he had heard from a certain learned man of iron ores, of the colour of
iron, but quite soft and fatty, which can be smoothed with the fingers like
butter, out of which excellent iron can be smelted: somewhat the same we
have seen found in England, having the aspect of Spanish soap. Besides the
numberless kinds of stony ores, iron is extracted from clay, from clayey
earth, from ochre, from a rusty matter deposited from chalybeate waters; In
England iron is copiously extracted in furnaces often from sandy and clayey
stones which appear to contain iron not more than sand, marl, or any other
clay soils contain it. Thus in Aristotle's book _De Mirabilibus
Auscultationibus_[74], "There is said" (he states) "to be a peculiar
formation of Chalybean and Misenian iron, for instance the sort collected
from river gravel; some say {23} that after being simply washed it is
smelted in the furnace; others declare that it and the sediment which
subsides after several washings are cast in and purified together by the
fire; with the addition of the stone pyrimachus which is found there in
abundance." Thus do numerous sorts of things contain in their various
substances notably and abundantly this element of iron and earth. However,
there are many stones, and very common ones, found in every soil, also
earths, and various and mixed materials, which do not hold rich substances,
but yet have their own iron elements, and yield them to skilfully-made
fires, yet which are left aside by metallick men because they are less
profitable; while other soils give some show of a ferruginous nature, yet
(being very barren) are hardly ever smelted down into iron; and being
neglected are not generally known. Manufactured irons differ very greatly
amongst themselves. For one kind is tenacious in its nature, and this is
the best; one is of medium quality: another is brittle, and this is the
worst. Sometimes the iron, by reason of the excellency of the ore, is
wrought into steel, as to-day in Noricum. From the finest iron, too, well
wrought and purged from all dross, or by being plunged in water after
heating, there issues what the Greeks call [Greek: stomôma]; the Latins
_acies;_ others _aciarium,_ such as was at times called Syrian, Parthian,
Noric, Comese, Spanish; elsewhere it is named from the water in which it is
so often plunged, as at Como in Italy[75], Bambola and Tarazona in Spain.
_Acies_ fetches a much larger price than mere iron. And owing to its
superiority it better accords with the loadstone, from which more powerful
quality it is often smelted, and it acquires the virtues from it more
quickly, retains them longer at their full, and in the best condition for
magnetical experiments. After iron has been smelted in the first furnaces,
it is afterward wrought by various arts in large worksteads or mills, the
metal acquiring consistency when hammered with ponderous blows, and
throwing off the dross. After the first smelting it is rather brittle and
by no means perfect. Wherefore with us (English) when the larger military
guns are cast, they purify the metal from dross more fully, so that they
may be stronger to withstand the force of the firing; and they do this by
making it pass again (in a fluid state) through a chink, by which process
it sheds its recremental matter. Smiths render iron sheets tougher with
certain liquids, and by blows of the hammer, and from them make shields and
breastplates that defy the blows of battle-axes. Iron becomes harder
through skill and proper tempering, but also by skill turns out in a softer
condition and as pliable as lead. It is made hard by the action of certain
waters into which while glowing it is plunged, as at Bambola and Tarazona
in Spain: It grows soft again, either by the effect of fire alone, when
without hammering and without water, it is left to cool by itself; or by
that of grease into which it is plunged; or {24} (that it may the better
serve for various trades) it is tempered variously by being skilfully
besmeared. Baptista Porta expounds this art in book 13 of his _Magia
Naturalis_. Thus this ferric and telluric nature is included and taken up
in various bodies of stones, ores, and earths; so too it differs in aspect,
in form, and in efficiency. Art smelts it by various processes, improves
it, and turns it, above all material substances, to the service of man in
trades and appliances without end. One kind of iron is adapted for
breastplates, another serves as a defence against shot, another protects
against swords and curved blades (commonly called scimitars), another is
used for making swords, another for horseshoes. From iron are made nails,
hinges, bolts, saws, keys, grids, doors, folding-doors, spades, rods,
pitchforks, hooks, barbs, tridents, pots, tripods, anvils, hammers, wedges,
chains, hand-cuffs, fetters, hoes, mattocks, sickles, baskets, shovels,
harrows, planes, rakes, ploughshares, forks, pans, dishes, ladles, spoons,
spits, knives, daggers, swords, axes, darts, javelins, lances, spears,
anchors, and much ship's gear. Besides these, balls, darts, pikes,
breastplates, helmets, cuirasses, horseshoes, greaves, wire, strings of
musical instruments, chairs, portcullises, bows, catapults, and (pests of
human kind) cannon, muskets, and cannon-balls, with endless instruments
unknown to the Latins: which things I have rehearsed in order that it may
be understood how great is the use of iron, which surpasses a hundred times
that of all the other metals; and is day by day being wrought by
metal-workers whose stithies are found in almost every village. For this is
the foremost of metals, subserving many and the greatest needs of man, and
abounds in the earth above all other metals, and is predominant. Wherefore
those Chemists are fools[76] who think that nature's will is to perfect all
metals into gold; she might as well be making ready to change all stones to
diamonds, since diamond surpasses all in splendour and hardness, because
gold excels in splendour, gravity, and density, being invincible against
all deterioration. Iron as dug up is therefore, like iron that has been
smelted, a metal, differing a little indeed from the primary homogenic
terrestrial body, owing to the metallick humour it has imbibed; yet not so
alien as that it will not, after the manner of refined matter, admit
largely of the magnetick forces, and may be associated with that prepotent
form belonging to the earth, and yield to it a due submission.
* * * * * {25}
CHAP. VIII.
In what countries and districts iron
_originates._
Plenty of iron mines exist everywhere, both those of old time recorded in
early ages by the most ancient writers, and the new and modern ones. The
earliest and most important seem to me to be those of Asia. For in those
countries which abound naturally in iron, governments and the arts
flourished exceedingly, and things needful for the use of man were
discovered and sought after. It is recorded to have been found about
Andria, in the region of the Chalybes near the river Thermodon in Pontus;
in the mountains of Palestine which face Arabia; in Carmania: in Africa
there was a mine of iron in the Isle of Meroe; in Europe in the hills of
Britain, as Strabo writes; in Hither Spain, in Cantabria. Among the
Petrocorii and Cubi Biturges[77] (peoples of Gaul), there were worksteads
in which iron used to be wrought. In greater Germany near Luna, as recorded
by Ptolemy; Gothinian iron is mentioned by Cornelius Tacitus; Noric iron is
celebrated in the verses of poets; and Cretan, and that of Euboea; many
other iron mines were passed over by these writers or unknown to them; and
yet they were neither poor nor scanty, but most extensive. Pliny[78] says
that Hither Spain and all the district from the Pyrenees is ferruginous,
and on the part of maritime Cantabria washed by the Ocean (says the same
writer) there is (incredible to relate) a precipitously high mountain
wholly composed of this material. The most ancient mines were of iron
rather than of gold, silver, copper or lead; since mainly this was sought
because of the demand; and also because in every district and soil they
were easy to find, not so deep-lying, and less beset by difficulties. If,
however, I were to enumerate modern iron workings, and those of this age
and over Europe only, I should have to write a large and bulky volume, and
sheets of paper would run short quicker than the iron, and yet for one
sheet they could furnish a thousand worksteads. For amongst minerals, no
material is so ample; all metals, and all stones distinct from iron, are
outdone by ferric and ferruginous matter. For you will not readily find any
region, and scarcely any country district over the whole of Europe (if you
search at all deeply), that does not either produce a rich and abundant
vein of iron or some soil containing or slightly charged with ferruginous
stuff; and that this is {26} true any expert in the arts of metals and
chemistry will easily find. Beside that which has ferruginous nature, and
the metallick lode, there is another ferric substance which does not yield
the metal in this way because its thin humour is burnt out by fierce fires,
and it is changed into an iron slag like that which is separated from the
metal in the first furnaces. And of this kind is all clay and argillaceous
earth, such as that which apparently forms a large part of the whole of our
island of Britain: all of which, if subjected very vehemently to intense
heat, exhibits a ferric and metallick body, or passes into ferric vitreous
matter, as can be easily seen in buildings in bricks baked from clay,
which, when placed next the fires in the open kilns (which our folk call
_clamps_)[79] and burned, present an iron vitrification, black at the other
end. Moreover all those earths as prepared are drawn by the magnet, and
like iron are attracted by it. So perpetual and ample is the iron offspring
of the terrestrial globe. Georgius Agricola says that almost all
mountainous regions are full of its ores, while as we know a rich iron lode
is frequently dug in the open country and plains over nearly the whole of
England and Ireland; in no other wise than as, says he, iron is dug out of
the meadows at the town of Saga in pits driven to a two-foot depth. Nor are
the West Indies without their iron lodes, as writers tell us; but the
Spaniards, intent upon gold, neglect the toilsome work of iron-founding,
and do not search for lodes and mines abounding in iron. It is probable
that nature and the globe of the earth are not able to hide, and are
evermore bringing to the light of day, a great mass of inborn matter, and
are not invariably obstructed by the settling of mixtures and
efflorescences at the earth's surface. It is not only in the common mother
(the terrestrial globe) that iron is produced, but sometimes also in the
air from the earth's exhalations, in the highest clouds. It rained iron in
Lucania, the year in which M. Crassus was slain. The tale is told, too,
that a mass of iron, like slag, fell from the air in the Nethorian forest,
near Grina, and they narrate that the mass was many pounds in weight; so
that it could neither be conveyed to that place, on account of its weight,
nor be brought away by cart, the place being without roads. This happened
before the civil war waged between the rival dukes in Saxony. A similar
story, too, comes to us from Avicenna. It once rained iron in the
Torinese[80], in various places (Julius Scaliger telling us that he had a
piece of it in his house), about three years before that province was taken
over by the king. In the year 1510 in the country bordering on the river
Abdua (as Cardan writes[81] in his book _De Rerum Varietate_) there fell
from the sky 1200 stones, one weighing 120 pounds, another 30 or 40 pounds,
of a rusty iron colour and remarkably hard. These occurrences being rare
are regarded as portents, like the showers of earth and stones mentioned in
Roman history. But that it ever rained other metals is not {27} recorded;
for it has never been known to rain from the sky gold, silver, lead, tin,
or spelter[82]. Copper, however, has been at some time noticed to fall from
the sky, and this is not very unlike iron; and in fact cloud-born iron of
this sort, or copper, are seen to be imperfectly metallick, incapable of
being cast in any way, or wrought with facility. For the earth hath of her
store plenty of iron in her highlands, and the globe contains the ferric
and magnetick element in rich abundance. The exhalations forcibly derived
from such material may well become concreted in the upper air by the help
of more powerful causes, and hence some monstrous progeny of iron be
begotten.
* * * * *
CHAP. IX.
Iron ore attracts iron ore.
From various substances iron (like all the rest of the * metals) is
extracted: such substances being stones, earth, and similar concretions
which miners call veins because it is in veins[83], as it were, that they
are generated. We have spoken above of the variety of these veins. If a
properly coloured ore of iron and a rich one (as miners call it) is placed,
as soon as mined, upon water in a bowl or any small vessel (as we have
shown before in the case of a loadstone), it is attracted by a similar
piece of ore brought near by hand, yet not so powerfully and quickly as one
loadstone is drawn by another loadstone, but slowly and feebly. Ores of
iron that are stony, cindery, dusky, red, and several more of other
colours, do not attract one another mutually, nor are they attracted by the
loadstone itself, even by a strong one, no more than wood, or lead, silver,
or gold. Take those ores and burn, or rather roast them, in a moderate
fire, so that they are not suddenly split up, or fly asunder, keeping up
the fire ten or twelve hours, and gently increasing it, then let them grow
cold, skill being shown in the direction in which they are placed: These
ores thus prepared a loadstone will now draw, and they now show a mutual
sympathy, and when skilfully arranged run together by their own forces.
* * * * *
{28}
CHAP. X.
*
Iron ore has poles, and acquires them, and settles
_itself toward the poles of the universe_.
Deplorable is man's ignorance in natural science, and modern philosophers,
like those who dream in darkness, need to be aroused, and taught the uses
of things and how to deal with them, and to be induced to leave the
learning sought at leisure from books alone, and that is supported only by
unrealities of arguments and by conjectures. For the knowledge of iron
(than which nothing is in more common use), and that of many more
substances around us, remains unlearned; iron, a rich ore of which, placed
in a vessel upon water, by an innate property of its own directs itself,
just like the loadstone, North and South, at which points it rests, and to
which, if it be turned aside, it reverts by its own inherent vigour. But
many ores, less perfect in their nature, which yet contain amid stone or
earthy substances plenty of iron, have no such motion; but when prepared by
skilful treatment in the fires, as shown in the foregoing chapter, they
acquire a polar vigour (which we call verticity[84]); and not only the iron
ores in request by miners, but even earth merely charged with ferruginous
matter, and many rocks, do in like manner tend and lean toward those
portions of the heavens, or more truly of the earth, if they be skilfully
placed, until they reach the desired location, in which they eagerly
repose.
* * * * *
{29} CHAP. XI.
*
Wrought Iron, not excited by a loadstone,
_draws iron_.
From the ore, which is converted, or separated, partly into metal, partly
into slag, by the intense heat of fires, iron is smelted in the first
furnaces in a space of eight, ten, or twelve hours, and the metal flows
away from the dross and useless matter, forming a large and long mass,
which being subjected to a sharp hammering is cut into parts, out of which
when reheated in the second hearth of the forge, and again placed on the
anvil, the smiths fashion quadrangular lumps, or more specially bars which
are bought by merchants and blacksmiths, from which in smithies usually it
is the custom to fashion the various implements. This iron we term
_wrought_, and its attraction by the loadstone is manifest to all. But we,
by more carefully trying everything[85], have found out that iron merely,
by itself alone, not excited by any loadstone, not charged by any alien
forces, attracts other iron; though it does not so eagerly snatch and
suddenly pluck at it as would a fairly strong loadstone; this you may know
thus: A small piece of cork, the size of a hazel-nut, rounded, is traversed
by an iron wire up to the middle of the wire: when set swimming on still
water apply to one end of it, close (yet so as not to touch), the end of
another iron wire; and wire draws wire, and one follows the other when
slowly drawn back, and this goes on up to the proper boundaries. Let A be
the cork with the iron wire, B one end of it raised a little above the
surface of the water, C the end of the second wire, showing the way in
which B is drawn by C. You may prove it in another way in a larger body.
Let a long bright iron rod (such as is made for hangings and window
curtains) be hung in balance by a slender silken cord: to one end of this
as it rests in the air bring a small oblong mass of polished iron, with its
proper {30} end at the distance of half a digit. The balanced iron turns
itself to the mass; do you with the same quickness draw back the mass in
your hand in a circular path about the point of equilibrium of the
suspension; the end of the balanced iron follows after it, and turns in an
orbit.
[Illustration]
* * * * *
CHAP. XII.
*
A long piece of Iron, even though not excited by a
_loadstone, settles itself toward North and South._
Every good and perfect piece of iron, if drawn out in length, points North
and South, just as the loadstone or iron rubbed with a magnetical body
does; a thing that our famous philosophers have little understood, who have
sweated in vain to set forth the magnetick virtues and the causes of the
friendship of iron for the stone. You may experiment with either large or
small iron works, and either in air or in water. A straight piece of iron
six feet long of the thickness of your finger is suspended (in the way
described in the foregoing chapter) in exact æquipoise by a strong and
slender silken cord. But the cord should be cross-woven of several silk
filaments, not twisted simply in one way; and it should be in a small
chamber with all doors and windows closed, that the wind may not enter, nor
the air of the room be in any way disturbed; for which reason it is not
expedient that the trial should be made on windy days, or while a storm is
brewing. For thus it freely follows its bent, and slowly moves until at
length, as it rests, it points with its ends North and South, just as iron
touched with a loadstone does in shadow-clocks, and in compasses, and in
the mariners' compass. You will be able, if curious enough, to balance all
at the same time by fine threads a number of small rods, or iron wires, or
long pins with which women knit stockings; you will see that all of them at
the same time are in accord, unless there be some error in this delicate
operation: for unless you prepare everything fitly and skilfully, the
labour will be void. Make trial of this thing in water also, which is done
both more certainly and more easily. Let an iron wire two or three digits
long, more or less, be passed through a round cork, so that it may just
float upon water; and as soon as you have committed it to the waves, it
turns upon its own centre, and one end tends to the North, the other to the
South; the causes {31} of which you will afterwards find in the laws of the
direction. This too you should understand, and hold firmly in memory, that
* as a strong loadstone, and iron touched with the same, do not invariably
point exactly to the true pole but to the point of the variation; so does a
weaker loadstone, and so does the iron, which directs itself by its own
forces only, not by those impressed by the stone; and so every ore of iron,
and all bodies naturally endowed with something of the iron nature, and
prepared, turn to the same point of the horizon, according to the place of
the variation in that particular region (if there be any variation
therein), and there abide and rest.
* * * * *
CHAP. XIII.
*
Wrought iron has in itself certain parts Boreal and Austral:
A magnetick vigour, verticity, and determinate
_vertices, or poles_.
Iron settles itself toward the North and South; not with one and the same
point toward this pole or that: for one end of the piece of ore itself and
one extremity also of a wrought-iron wire have a sure and constant
destination to the North, the other to the South, whether the iron hang in
the air, or float on water, be the iron large rods or thinner wires. Even
if it be a little rod, or a wire ten or twenty or more ells in length; one
end as a rule is Boreal, the other Austral. If you cut off part of that
wire, and if the end of that divided part were Boreal, the other end (which
was joined to it) will be Austral. Thus if you divide it into several
parts, before making an experiment on the surface of water, you can
recognize the vertex[86]. In all of them a Boreal end draws an Austral and
repels a Boreal, and contrariwise, according to the laws magnetical. Yet
herein wrought iron differs from the loadstone and from its own ore,
inasmuch as in an iron ball of any size, such as those used for artillery
or cannon, or bullets used for carbines or fowling-pieces, verticity is
harder to acquire and is less apparent than in a piece of loadstone, or of
ore itself, or than in a round loadstone. But in long and extended pieces
of iron a power is at once discerned; the causes of which fact, and the
methods by which it acquires its verticity and its poles without use of a
loadstone, as well as the reasons for all the other obscure features of
verticity, we shall set forth in describing the motion of direction.
* * * * *
{32} CHAP. XIIII.
Concerning other powers of loadstone, and its
_medicinal properties_.
Dioscorides prescribes loadstone to be given with sweetened water, three
scruples' weight, to expel gross humours. Galen writes that a like quantity
of bloodstone avails. Others relate that loadstone perturbs the mind and
makes folk melancholick, and mostly kills. Gartias ab Horto[87] thinks it
not deleterious or injurious to health. The natives of East India tell us,
he says, that loadstone taken in small doses preserves youth. On which
account the aged king, Zeilam, is said to have ordered the pans in which
his victuals were cooked to be made of loadstone. The person (says he) to
whom this order was given told me so himself. There are many varieties of
loadstone produced by differences in the mingling of earths, metals, and
juices; hence they are altogether unlike in their virtues and effects, due
to propinquities of places and of agnate bodies, and arising from the pits
themselves as it were from the matrices being soul. One loadstone is
therefore able to purge the stomach, and another to check purging, to cause
by its fumes a serious shock to the mind, to produce a gnawing at the
vitals, or to bring on a grave relapse; in case of which ills they exhibit
gold and emerald, using an abominable imposture for lucre. Pure loadstone
may, indeed, be not only harmless, but even able to correct an over-fluid
and putrescent state of the bowels and bring them back to a better
temperament; of this sort usually are the oriental magnets from China, and
the denser ones from Bengal, which are neither misliking nor unpleasant to
the actual senses. Plutarch and Claudius Ptolemy[88], and all the copyists
since their time, think that a loadstone smeared with garlick does not
allure iron. Hence some suspect that garlick is of avail against any
deleterious power of the magnet: thus in philosophy many false and idle
conjectures arise from fables and falsehoods. Some physicians[89] have that
a loadstone has power to extract the iron of an arrow from the human body.
But it is when whole that the loadstone draws, not when pulverized and
formless, buried in plasters; for it does not attract by reason of its
material, but is rather adapted for the healing of open wounds, by reason
of exsiccation, closing up and drying the sore, an effect by which the
arrow-heads would rather be retained in the wounds. Thus vainly and
preposterously do the sciolists {33} look for remedies while ignorant of
the true causes of things. The application of a loadstone for all sorts of
headaches no more cures them (as some make out) than would an iron helmet
or a steel cap. To give it in a draught to dropsical persons is an error of
the ancients, or an impudent tale of the copyists, though one kind of ore
may be found which, like many more minerals, purges the stomach; but this
is due to some defect of that ore and not to any magnetick property.
Nicolaus puts a large quantity of loadstone into his divine plaster[90],
just as the Augsburgers do into a black plaster[91] for fresh wounds and
stabs; the virtue of which dries them up without smart, so that it proves
an efficacious medicament. In like manner also Paracelsus to the same end
mingles it in his plaster for stab wounds[92].
* * * * *
CHAP. XV.
The Medicinal Virtue of Iron.[93]
Not foreign to our present purpose will it be to treat briefly also of the
medicinal virtue of iron: for it is a prime remedial for some diseases of
the human body, and by its virtues, both those that are natural and those
acquired by suitable preparation, it works marvellous changes in the human
body, so that we may the more surely recognize its nature through its
medicinal virtue and through certain manifest experiments. So that even
those tyros in medicine who abuse this most famous medicament may learn to
prescribe it with better judgment for the healing of the sick, and not, as
too often they use it, to their harm. The best iron, Stomoma, or Chalybs,
Acies, or Aciarium, is reduced to a fine powder by a file; the powder is
steeped in the sharpest vinegar, and dried in the sun, and again soused in
vinegar, and dried; afterwards it is washed in spring water or other
suitable water, and dried; then for the second time it is pulverized and
reduced on porphyry, passed through a very fine sieve, and put back for
use. It is given chiefly in cases of laxity and over-humidity of the liver,
in enlargement of the spleen, after due evacuations; for which reason it
restores young girls when pallid, sickly, and lacking colour, to health and
beauty; since it is very siccative, and is astringent without harm. But
some who in every internal malady always talk of obstruction {34} of the
liver and spleen, think it beneficial in those cases because it removes
obstructions, mainly trusting to the opinions of certain Arabians[94]:
wherefore they administer it to the dropsical and to those suffering from
tumour of the liver or from chronic jaundice, and to persons troubled with
hypochondrical melancholia or any stomachic disorder, or add it to
electuaries, without doubt to the grievous injury of many of their
patients. Fallopius commends it prepared in his own way for tumours of the
spleen, but is much mistaken; for loadstone is pre-eminently good for
spleens relaxed with humour, and swollen; but it is so far from curing
spleens thickened into a tumour that it mightily confirms the malady. For
those drugs which are strong siccatives and absorb humour force the viscera
when hardened into a tumour more completely into a quasi-stony body. There
are some who roast iron in a closed oven with fierce firing, and burn it
strongly, until it turns red, and they call this Saffron of Mars; which is
a powerful siccative, and more quickly penetrates the intestines. Moreover
they order violent exercise, that the drug may enter the viscera while
heated and so reach the place affected; wherefore also it is reduced to a
very fine flour; otherwise it only sticks in the stomach and in the chyle
and does not penetrate to the intestines. As a dry and earthy medicament,
then, it is shown by the most certain experiments to be, after proper
evacuations, a remedy for diseases arising from humour (when the viscera
are charged and overflowing with watery rheum). Prepared steel is a
medicament proper for enlarged spleen. Iron waters too are effectual in
reducing the spleen, although as a rule iron is of a frigid and astringent
efficiency, not a laxative; but it effects this neither by heat nor by
cold, but from its own dryness when mixed with a penetrative fluid: it thus
disperses the humour, thickens the villi, hardens the tissues, and
contracts them when lax; while the inherent heat in the member thus
strengthened, being increased in power, dissipates what is left. Whereas if
the liver be hardened and weakened by old age or a chronic obstruction, or
the spleen be shrivelled and contracted to a schirrus, by which troubles
the fleshy parts of the limbs grow flaccid, and water under the skin
invades the body, in the case of these conditions the introduction of iron
accelerates the fatal end, and considerably increases the malady. Amongst
recent writers there are some who in cases of drought of the liver
prescribe, as a much lauded and famous remedy, the electuary of iron slag,
described by Rhazes[95] in his ninth book _ad Almansorem_, Chap. 63, or
prepared filings of steel; an evil and deadly advice: which if they do not
some time understand from our philosophy, at least everyday experience, and
the decline and death of their patients, will convince them, even the
sluggish and lazy. Whether iron be warm or cold is variously contended by
{35} many. By Manardus, Curtius, Fallopius and others, many reasons are
adduced on both sides; each settles it according to his own sentiment. Some
make it to be cold, saying that iron has the property of refrigerating,
because Aristotle in his _Meteorologica_ would put iron in the class of
things which grow concreted in cold by emission of the whole of their Heat:
Galen, too, says that iron has its consistency from cold; also that it is
an earthy and dense body. Further that iron is astringent, also that
Chalybeate water quenches thirst: and they adduce the cooling effect of
thermal iron waters. Others, however, maintain that it is Warm, because of
Hippocrates making out that waters are warm which burst forth from places
where iron exists. Galen says that in all metals there is considerable
substance, or essence, of fire. Paolo[96] affirms that iron waters are
warm. Rhazes will have it that iron is warm and dry in the third degree.
The Arabians think that it opens the spleen and liver; wherefore also that
iron is warm. Montagnana recommends it in cold affections of the uterus and
stomach. Thus do the smatterers cross swords together, and puzzle inquiring
minds by their vague conjectures, and wrangle for trifles as for goats'
wool, when they philosophize, wrongly allowing and accepting properties:
but these matters will appear more plainly by and by when we begin to
discuss the causes of things; the clouds being dispersed that have so
darkened all Philosophy. Filings, scales, and slag of iron are, as Avicenna
makes out, not wanting in deleterious power (haply when they are not well
prepared or are taken in larger quantity than is fit), hence they cause
violent pain in the bowels, roughness of the mouth and tongue, marasmus,
and shrivelling of the limbs. But Avicenna wrongly[97] and old-womanishly
makes out that the proper antidote to this iron poison is loadstone to the
weight of a drachm taken as a draught in the juice of mercurialis or of
Beet; for loadstone is of a twofold nature, usually malefiant and
pernicious, nor does it resist iron, since it attracts it; nor when drunk
in a draught in the form of powder does it avail to attract or repel, but
rather inflicts the same evils.
* * * * * {36}
CHAP. XVI.
That loadstone & iron ore are the same, but iron an
_extract from both, as other metals are from their own_
ores; & that all magnetick virtues, though
_weaker, exist in the ore itself & in
smelted iron._
Hitherto we have declared the nature & powers of the loadstone, & also the
properties & essence of iron; it now remains to show their mutual
affinities, & kinship, so to speak, & how very closely conjoined these
substances are. At the highest part of the terrestrial globe, or at its
perishable surface & rind, as it were, these two bodies usually originate &
are produced in one and the same matrix, as twins in one mine. Strong
loadstones are dug up by themselves, weaker ones too have their own proper
vein. Both are found in iron mines. Iron ore most often occurs alone,
without strong loadstone (for the more perfect are rarely met with). Strong
loadstone is a stone resembling iron; out of it is usually smelted the
finest iron, which the Greeks call _stomoma_, the Latins _acies_, the
Barbarians (not amiss) _aciare_, or _aciarium_. This same stone draws,
repels, controls other loadstones, directs itself to the poles of the
world, picks up smelted iron, and works many other wonders, some already
set forth by us, but many more which we must demonstrate more fully. A
weaker loadstone, however, will exhibit all these powers, but in a lesser
degree; while iron ore, & also wrought iron (if they have been prepared)
show their strength in all magnetick experiments not less than do feeble
and weak * loadstones; & an inert piece of ore, & one possessed of no
magnetick properties, & just thrown out[98] of the pit, when roasted in the
fire & prepared with due art (by the elimination of humours & foreign
excretions) awakes, and becomes in power & potency a magnet, * occasionally
a stone or iron ore is mined, which attracts forthwith without being
prepared: for native iron of the right colour attracts and governs iron
magnetically. One form then belongs to the one mineral, one species, one
self-same essence. For to me there seems to be a greater difference, &
unlikeness, between the strongest {37} loadstone, & a weak one which scarce
can attract a single chip of iron; between one that is stout, strong,
metallick, & one that is soft, friable, clayey; amidst such variety of
colour, substance, quality, & weight; than there is on the one hand between
the best ore, rich in iron, or iron that is metallick from the beginning,
and on the other the most excellent loadstone. Usually, too, there are no
marks to distinguish them, and even metallurgists cannot decide between
them, because they agree together in all respects. Moreover we see that the
best loadstone and the ore of iron are both as it were distressed by the
same maladies & diseases, both run to old age in the same way & exhibit the
same marks of it, are preserved & keep their properties by the same
remedies & safeguards; & yet again the one increases the potency of the
other, & by artfully devised adjuncts marvellously intensifies, & exalts
it. For both are impaired by the more acrid juices as by poisons, & the
aqua fortis of the Chemists inflicts on both the same wounds, and when
exposed too long to harm from the atmosphere, they both alike pine away, so
to speak, & grow old; each is preserved by being kept in the dust &
scrapings of the other; & when a fit piece of steel or iron is adjoined
above its pole, the loadstone's vigour is augmented through the firm union.
The loadstone is laid up in iron filings, not that iron is its food; as
though loadstone were alive and needed feeding, as Cardan
philosophizes[99]; nor yet that so it is delivered from the inclemency of
the weather (for which cause it as well as iron is laid up in bran by
Scaliger; mistakenly, however, for they are not preserved well in this way,
and keep for years their own fixed forms): nor yet, since they remain
perfect by the mutual action of their powders, do their extremities waste
away, but are cherished & preserved, like by like. For just as in their own
places, in the mines, bodies like to each other endure for many ages entire
and uncorrupt, when surrounded by bodies of the same stuff, as the lesser
interior parts in a great mass: so loadstone and ore of iron, when inclosed
in a mound of the same material, do not exhale their native humour, do not
waste away, but retain their soundness. A loadstone lasts longer in filings
of smelted iron, & a piece of iron ore excellently also in dust of
loadstone; as also smelted iron in filings of loadstone & even in those of
iron. Then both these allied bodies have a true & just form of one & the
same species; a form which until this day was considered by all, owing to
their outward unlikeness & the inequality of the potency that is the same
innate in both, to be different & unlike in kind; the smatterers not
understanding that the same powers, though differing in strength, exist in
both alike. And in fact they both are true & intimate parts of the earth, &
as such retain the prime natural properties of mutually attracting, of
moving, & of disposing themselves toward the position of the world, {38}
and of the terrestrial globe; which properties they also impart to each
other, and increase, confirm, receive, and retain each other's forces. The
stronger fortifies the weaker, not as though aught were taken away from its
own substance, or its proper vigour, nor because any corporeal substance is
imparted, but the dormant virtue of the one is aroused by the other,
without loss. For if with a single small stone you touch a thousand bits of
iron for the use of mariners[100], that loadstone attracts iron no less
strongly than before; with the same stone weighing one pound, any one will
be able to suspend in the air a thousand pounds of iron. For if any one
were to fix high up on the walls so many iron nails of so great a weight, &
were to apply to them the same number of nails touched, according to the
art, by a loadstone, they would all be seen to hang in the air through the
force of one small stone. So this is not solely the action, labour, or
outlay of the loadstone; but the iron, which is in a sense an extract from
loadstone, and a fusion of loadstone into metal, & conceives vigour from
it, & by proximity strengthens the magnetick faculties, doth itself, from
whatever lode it may have come, raise its own inborn forces through the
presence & contact of the stone, even when solid bodies intervene. Iron
that has been touched, acts anew on another piece of iron by contact, &
adapts it for magnetick movements, & this again a third. But if you rub
with a loadstone any other metal, or wood, or bones, or glass, as they will
not be moved toward any particular and determinate quarter of heaven, nor
be attracted by any magnetick body, so they are able not to impart any
magnetick property to other bodies or to iron itself by attrition, & by
infection. Loadstone differs from iron ore, as also from some weaker
magnets, in that when molten in the furnace into a ferric & metallick fused
mass, it does not so readily flow & dissolve into metal; but is sometimes
burnt to ashes in large furnaces; a result which it is reasonable to
suppose arises from its having some kind of sulphureous matter mixed with
it, or from its own excellence & simpler nature, or from the likeness &
common form which it has with the common mother, the Great Magnet. For
earths, and iron stones, magnets abounding in metal, are the more imbued &
marred with excrementitious metallick humours, and earthy corruptions of
substance, as numbers of loadstones are weaker from the mine; hence they
are a little further remote from the common mother, & are degenerate, &
when smelted in the furnace undergo fusion more easily, & give out a more
certain metallick product, & a metal that is softer, not a tough steel. The
majority of loadstones (if not unfairly burnt[101]) yield in the furnace a
very excellent iron. But iron ore also agrees in all those primary
qualities with loadstone; for both, being nearer and more closely akin to
the earth above all bodies known to us, have in themselves {39} a magnetick
substance, & one that is more homogenic, true & cognate with the globe of
the earth; less infested & spoiled by foreign blemish; less confused with
the outgrowths of earth's surface, & less debased by corrupt products. And
for this reason Aristotle in the fourth book of his _Meteora_ seems not
unfairly to separate iron from all the rest of the metals. Gold, he says,
silver, copper, tin, lead, belong to water; but iron is of the earth.
Galen, in the fourth chapter of _De Facultatibus Simplicium
Medicamentorum_, says that iron is an earthy & dense body. Accordingly a
strong loadstone is on our showing especially of the earth: the next place
is occupied by iron ore or weaker loadstone; so the loadstone is by nature
and origin[102]** of iron, and it and magnetick iron are both one in kind.
Iron ore yields iron in furnaces; loadstone also pours forth iron in the
furnaces, but of a much more excellent sort, that which is called steel or
blade-edge; and the better sort of iron ore is a weak loadstone, the best
loadstone being a most excellent ore of iron, in which, as is to be shown
by us, the primary properties are grand and conspicuous. Weaker loadstone
or iron ore is that in which these properties are more obscure, feeble, and
are scarce perceptible to the senses.
* * * * *
CHAP. XVII.
That the globe of the earth is magnetick, & a magnet; &
_how in our hands the magnet stone has all the primary_
forces of the earth, while the earth by the
_same powers remains constant in a
fixed direction in the
universe._
Prior to bringing forward the causes of magnetical motions, & laying open
the proofs of things hidden for so many ages, & our experiments (the true
foundations of terrestrial philosophy), we have to establish & present to
the view of the learned our New & unheard of doctrine about the earth; and
this, when argued by us on the grounds of its probability, with subsequent
{40} experiments & proofs, will be as certainly assured as anything in
philosophy ever has been considered & confirmed by clever arguments or
mathematical proofs. The terrene mass, which together with the vasty ocean
produces the sphærick figure & constitutes our globe, being of a firm &
constant substance, is not easily changed, does not wander about, &
fluctuate with uncertain motions, like the seas, & flowing waves: but holds
all its volume of moisture in certain beds & bounds, & as it were in
oft-met veins, that it may be the less diffused & dissipated at random. Yet
the solid magnitude of the earth prevails & reigns supreme in the nature of
our globe. Water, however, is attached to it, & as an appendage only, & a
flux emanating from it; whose force from the beginning is conjoined with
the earth through its smallest parts, and is innate in its substance. This
moisture the earth as it grows hot throws off freely when it is of the
greatest possible service in the generation of things. But the thews and
dominant stuff of the globe is that terrene body which far exceeds in
quantity all the volume of flowing streams and open waters (whatever vulgar
philosophers may dream of the magnitudes and proportions of their
elements), and which takes up most of the whole globe and almost fills it
internally, and by itself almost suffices to endow it with sphærick shape.
For the seas only fill certain not very deep or profound hollows, since
they rarely go down to a depth of a mile and generally do not exceed a
hundred or 50 fathoms. For so it is ascertained by the observations of
seamen when by the plumb-line and sinker its abysms are explored with the
nautical sounder; which depths relatively to the dimensions of the globe,
do not much deform its globular shape. Small then appears to be that
portion of the real earth that ever emerges to be seen by man, or is turned
up; since we cannot penetrate deeper into its bowels, further than the
wreckage of its outer efflorescence, either by reason of the waters which
gush up in deep workings, as through veins, or for want of a wholesome air
to support life in the miners, or on account of the vast cost that would be
incurred in pumping out such huge workings[103], and many other
difficulties; so that to have gone down to a depth of four hundred, or
(which is of rarest occurrence) of five hundred fathoms[104] as in a few
mines, appears to all a stupendous undertaking. But it is easy to
understand how minute, how almost negligibly small a portion that 500
fathoms is of the earth's diameter, which is 6,872 miles. It is then parts
only of the earth's circumference and of its prominences that are perceived
by us with our senses; and these in all regions appear to us to be either
loamy, or clayey, or sandy, or full of various soils, or marls: or lots of
stones or gravel meet us, or beds of salt, or a metallick lode, and metals
in abundance. In the sea and in deep waters, however, either reefs, and
huge boulders, or smaller stones, or sands, or mud {41} are found by
mariners as they sound the depths. Nowhere does the Aristotelian element of
_earth_ come to light; and the Peripateticks are the sport of their own
vain dreams about elements. Yet the lower bulk of the earth and the inward
parts of the globe consist of such bodies; for they could not have existed,
unless they had been related to and exposed to the air and water, and to
the light and influences of the heavenly bodies, in like manner as they are
generated, and pass into many dissimilar forms of things, and are changed
by a perpetual law of succession. Yet the interior parts imitate them, and
betake themselves to their own source, on the principle of terrene matter,
albeit they have lost the first qualities and the natural terrene form, and
are borne towards the earth's centre, and cohære with the globe of the
earth, from which they cannot be wrenched asunder except by force. But the
loadstone and all magneticks, not the stone only, but every magnetick
homogenic substance, would seem to contain the virtue of the earth's core
and of its inmost bowels, and to hold within itself and to have conceived
that which is the secret and inward principle of its substance; and it
possesses the actions peculiar to the globe of attracting, directing,
disposing, rotating, stationing itself in the universe, according to the
rule of the whole, and it contains and regulates the dominant powers of the
globe; which are the chief tokens and proofs of a certain distinguishing
combination, and of a nature most thoroughly conjoint. For if among actual
bodies one sees something move and breathe, and experience sensations, and
be inclined and impelled by reason, will one not, knowing and seeing this,
conclude that it is a man or something rather like a man, than that it is a
stone or a stick? The loadstone far excels all other bodies known to us in
virtues and properties pertaining to the common mother: but those
properties have been far too little understood or realized by philosophers:
for to its body bodies magnetical rush in from all sides and cleave to it,
as we see them do in the case of the earth. It has poles, not mathematical
points, but natural termini of force excelling in primary efficiency by the
co-operation of the whole: and there are poles in like manner in the earth
which our forefathers sought ever in the sky: it has an æquator, a natural
dividing line between the two poles, just as the earth has: for of all
lines drawn by the mathematicians on the terrestrial globe, the æquator is
the natural boundary, and is not, as will hereafter appear, merely a
mathematical circle. It, like the earth, acquires Direction and stability
toward North and South, as the earth does; also it has a circular motion
toward the position of the earth, wherein it adjusts itself to its rule: it
follows the ascensions and declinations of the earth's poles, and conforms
exactly to the same, and by itself raises its own poles above the {42}
horizon naturally according to the law of the particular country and
region, or sinks below it. The loadstone derives temporary properties, and
acquires its verticity from the earth, and iron is affected by the
verticity of the globe even as iron is by a loadstone: Magneticks are
conformable to and are regulated by the earth, and are subject to the earth
in all their motions. All its movements harmonize with, and strictly wait
upon, the geometry and form of the earth, as we shall afterwards prove by
most conclusive experiments and diagrams; and the chief part of the visible
earth is also magnetical, and has magnetick motions, although it be
disfigured by corruptions and mutations without end. Why then do we not
recognize this the chief homogenic substance of the earth, likest of
substances to its inner nature and closest allied to its very marrow? For
none of the other mixed earths suitable for agriculture, no other
metalliferous veins, nor stones, nor sand, nor other fragments of the earth
which have come to our view possess such constant and peculiar powers. And
yet we do not assume that the whole interior of this globe of ours is
composed of stones or iron (although Franciscus Maurolycus, that learned
man, deems the whole of the earth's interior to consist of solid stone).
For not every loadstone that we have is a stone, it being sometimes like a
clod, or like clay and iron either firmly compacted together out of various
materials, or of a softer composition, or by heat reduced to the metallick
state; and the magnetick substance by reason of its location and of its
surroundings, and of the metallick matrix itself, is distinguished, at the
surface of the terrene mass, by many qualities and adventitious natures,
just as in clay it is marked by certain stones and iron lodes. But we
maintain that the true earth is a solid substance, homogeneous with the
globe, closely coherent, endowed with a primordial and (as in the other
globes of the universe) with a prepotent form; in which position it
persists with a fixed verticity, and revolves with a necessary motion and
an inherent tendency to turn, and it is this constitution, when true and
native, and not injured or disfigured by outward defects, that the
loadstone possesses above all bodies apparent to us, as if it were a more
truly homogenic part taken from the earth. Accordingly native iron which
_sui generis_ (as metallurgists term it), is formed when homogenic parts of
the earth grow together into a metallick lode; Loadstone being formed when
they are changed into metallick stone, or a lode of the finest iron, or
steel: so in other iron lodes the homogenic matter that goes together is
somewhat more imperfect; just as many parts of the earth, even the high
ground, is homogenic but so much more deformate. Smelted iron is fused and
smelted out of homogenic stuffs, and cleaves to the earth more tenaciously
than the ores themselves. Such then is our earth in its {43} inward parts,
possessed of a magnetick homogeneal nature, and upon such more perfect
foundations as these rests the whole nature of things terrestrial,
manifesting itself to us, in our more diligent scrutiny, everywhere in all
magnetick minerals, and iron ores, in all clay, and in numerous earths and
stones; while Aristotle's simple element, that most empty terrestrial
phantom of the Peripateticks, a rude, inert, cold, dry, simple matter, the
universal substratum, is dead, devoid of vigour, and has never presented
itself to any one, not even in sleep, and would be of no potency in nature.
Our philosophers were only dreaming when they spoke of a kind of simple and
inert matter. Cardan does not consider the loadstone to be any kind of
stone, "but a sort of perfected portion of some kind of earth that is
absolute; a token of which is its abundance, there being no place where it
is not found. And there is" (he says) "a power of iron in the wedded Earth
which is perfect in its own kind when it has received fertilizing force
from the male, that is to say, the stone of Hercules" (in his book _De
Proportionibus_). And later: "Because" (he says) "in the previous
proposition I have taught that iron is true earth." A strong loadstone
shows itself to be of the inward earth, and upon innumerable tests claims
to rank with the earth in the possession of a primary form, that by which
Earth herself abides in her own station and is directed in her courses.
Thus a weaker loadstone and every ore of iron, and nearly all clay, or
clayey earth, and numerous other sorts (yet more, or less, owing to the
different labefaction of fluids and slimes), keep their magnetick and
genuine earth-properties open to view, falling short of the characteristic
form, and deformate. For it is not iron alone (the smelted metal) that
points to the poles, nor is it the loadstone alone that is attracted by
another and made to revolve magnetically; but all iron ores, and other
stones, as Rhenish slates and the black ones from Avignon (the French call
them _Ardoises_) which they use for tiles, and many more of other colours
and substances, provided they have been prepared; as well as all clay,
grit[105], and some sorts of rocks, and, to speak more clearly, all the
more solid earth that is everywhere apparent; given that that earth be not
fouled with fatty and fluid corruptions; as mud, as mire, as accumulations
of putrid matter; nor deformate by the imperfections of sundry admixtures;
nor dripping with ooze, as marls; all are attracted by the loadstone, when
simply prepared by fire, and freed from their refuse humour; and as by the
loadstone so also by the earth herself they are drawn and controlled
magnetically, in a way different from all other bodies; and by that
inherent force settle themselves according to the orderly arrangement and
fabric of the universe and of the Earth, as will appear {44} later. Thus
every part of the earth which is removed from it exhibits by sure
experiments every impulse of the magnetick nature; by its various motions
it observes the globe of the earth and the principle common to both.
[Illustration]
* * * * *
{45} [Illustration]
BOOK SECOND.
_CHAP. I._
ON MAGNETICK
Motions.
Divers things concerning opinions about the magnet-stone, and its variety,
concerning its poles and its known faculties, concerning iron, concerning
the properties of iron, concerning a magnetick substance common to both of
these and to the earth itself, have been spoken briefly by us in the former
book. There remain the magnetical motions, and their fuller philosophy,
shown and demonstrated. These motions are incitements of homogeneal parts
either among themselves or toward the primary conformation of the whole
earth. Aristotle admits only two simple motions of his elements, from the
centre and toward the centre; of light ones upward, heavy ones downward; so
that in the earth there exists one motion only of all its parts towards the
centre of the world,--a rude and inert precipitation. But what of it is
light, and how wrongly it is inferred by the Peripateticks from the simple
motion of the elements, and also what is its heavy part, we will discuss
elsewhere. But now our inquiry must be into the causes of other motions,
depending on its true form, which we have plainly seen in our magnetick
bodies; and these we have seen to be present in the earth and in all its
homogenic parts also. We have noticed that they harmonize with the earth,
and are bound up with its forces. Five movements[106] or differences of
motions are then observed by us: Coition (commonly called attraction), the
{46} incitement to magnetick union; Direction towards the poles of the
earth, and the verticity and continuance of the earth towards the
determinate poles of the world; Variation, a deflexion from the meridian,
which we call a perverted movement; Declination, a descent of the magnetick
pole below the horizon; and circular motion, or Revolution. Concerning all
these we shall discuss separately, and how they all proceed from a nature
tending to aggregation, either by verticity or by volubility. Jofrancus
Offusius[107] makes out different magnetick motions; a first toward a
centre; a second toward a pole at seventy-seven degrees; a third toward
iron; a fourth toward loadstone. The first is not always to a centre, but
exists only at the poles in a straight course toward the centre, if the
motion is magnetick; otherwise it is only motion of matter toward its own
mass and toward the globe. The second toward a pole at seventy-seven
degrees is no motion, but is direction with respect to the pole of the
earth, or variation. The third and fourth are magnetick and are the same.
So he truly recognizes no magnetick motion except the Coition toward iron
or loadstone, commonly called attraction. There is another motion in the
whole earth, which does not exist towards the terrella or towards its
parts; videlicet, a motion of aggregation, and that movement of matter,
which is called by philosophers a right motion, of which elsewhere.
* * * * *
CHAP. II.
On the Magnetick Coition, and first on the
Attraction of Amber, or more truly, on the
_Attaching of Bodies to Amber_.
Celebrated has the fame of the loadstone and of amber ever been in the
memoirs of the learned. Loadstone and also amber do some philosophers
invoke when in explaining many secrets their senses become dim and
reasoning cannot go further. Inquisitive theologians also would throw light
on the divine mysteries set beyond the range of human sense, by means of
loadstone and amber; just as idle Metaphysicians, when they are setting up
and teaching useless phantasms, have recourse to the loadstone as if it
were a Delphick sword, an illustration always applicable to everything. But
physicians even (with the authority of {47} Galen), desiring to confirm the
belief in the attraction of purgative medicines by means of the likeness of
substance and the familiarities of the juices--truly a vain and useless
error--bring in the loadstone as witness as being a nature of great
authority and of conspicuous efficacy and a remarkable body. So in very
many cases there are some who, when they are pleading a cause and cannot
give a reason for it, bring in loadstone and amber as though they were
personified witnesses. But these men (apart from that common error) being
ignorant that the causes of magnetical motions are widely different from
the forces of amber, easily fall into error, and are themselves the more
deceived by their own cogitations. For in other bodies a conspicuous force
of attraction manifests itself otherwise than in loadstone; like as in
amber, concerning which some things must first be said, that it may appear
what is that attaching of bodies, and how it is different from and foreign
to the magnetical actions; those mortals being still ignorant, who think
that inclination to be an attraction, and compare it with the magnetick
coitions. The Greeks call it [Greek: êlektron][108] because it attracts
straws to itself, when it is warmed by rubbing; then it is called [Greek:
harpax][109]; and [Greek: chrusophoron] from its golden colour. But the
Moors call it Carabe[110], because they are accustomed to offer the same in
sacrifices and in the worship of the Gods. For Carab signifies to offer in
Arabic; so Carabe, an offering: or seizing chaff, as Scaliger quotes from
Abohalis, out of the Arabic or Persian language. Some also call it Amber,
especially the Indian and Ethiopian amber, called in Latin _Succinum_, as
if it were a juice[111]. The Sudavienses or Sudini[112] call it _geniter_,
as though it were generated terrestrially. The errors of the ancients
concerning its nature and origin having been exploded, it is certain that
amber comes for the most part from the sea, and the rustics collect it on
the coast after the more violent storms, with nets and other tackle; as
among the Sudini of Prussia; and it is also found sometimes on the coast of
our own Britain. It seems, however, to be produced also in the soil and at
spots of some depth, like other bitumens; to be washed out by the waves of
the sea; and to become concreted more firmly from the nature and saltness
of the sea-water. For it was at first a soft and viscous material;
wherefore also it contains enclosed and entombed in pieces of it, shining
in eternal sepulchres, flies, grubs, gnats, ants; which have all flown or
crept or fallen into it when it first flowed forth in a liquid state[113].
The ancients and also more recent writers recall (experience proving the
same thing), that amber attracts straws and chaff[114]. The same is also
done by jet[115], which is dug out of the earth in Britain, in Germany, and
in very many lands, and is a rather hard concretion from black bitumen, and
as it were a transformation into stone. There are many modern authors[116]
who have written and copied from others about amber and jet[117] attracting
chaff, and about other {48} substances generally unknown; with whose
labours the shops of booksellers are crammed. Our own age has produced many
books about hidden, abstruse, and occult causes and wonders, in all of
which amber and jet are set forth as enticing chaff; but they treat the
subject in words alone, without finding any reasons or proofs from
experiments, their very statements obscuring the thing in a greater fog,
forsooth in a cryptic, marvellous, abstruse, secret, occult, way. Wherefore
also such philosophy produces no fruit, because very many philosophers,
making no investigation themselves, unsupported by any practical
experience, idle and inert, make no progress by their records, and do not
see what light they can bring to their theories; but their philosophy rests
simply on the use of certain Greek words, or uncommon ones; after the
manner of our gossips and barbers nowadays, who make show of certain Latin
words to an ignorant populace as the insignia of their craft, and snatch at
the popular favour. For it is not only amber and * jet (as they suppose)
which entice small bodies[118]; but Diamond, Sapphire, Carbuncle, Iris
gem[119], Opal, Amethyst, Vincentina, and Bristolla (an English gem or
spar)[120], Beryl, and Crystal[121] do the same. Similar powers of
attraction are seen also to be possessed by glass (especially when clear
and lucid), as also by false gems made of glass or Crystal, by glass of
antimony, and by many kinds of spars from the mines, and by Belemnites.
Sulphur also attracts, and mastick, and hard sealing-wax[122] compounded of
lac tinctured of various colours. Rather hard resin entices, as does
orpiment[123], but less strongly; with difficulty also and indistinctly
under a suitable dry sky[124], Rock salt, muscovy stone, and rock alum.
This one may see when the air is sharp and clear and rare in mid-winter,
when the emanations from the earth hinder electricks less, and the
electrick bodies become * more firmly indurated; about which hereafter.
These substances draw everything, not straws and chaff only[125], but all
metals, woods, leaves, stones, earths, even water and oil, and everything
which is subject to our senses, or is solid; although some write that amber
does not attract anything but chaff and certain twigs; (wherefore Alexander
Aphrodiseus falsely declares the question of amber to be inexplicable,
because it attracts dry chaff only, and not basil leaves[126]), but these
are the utterly false and disgraceful tales of the writers. But in order
that you may be able clearly to test how such attraction occurs[127], and
what those materials[128] are which thus entice other bodies (for even if
bodies incline towards some of these, yet on account of weakness they seem
not to be raised by them, but are more easily turned), make yourself a
versorium of any metal you like, three or four digits in length, resting
rather lightly on its point of support after the manner of a magnetick
needle, to one end of which bring up a piece of amber or a smooth {49}
[Illustration] and polished gem which has been gently rubbed; for the
versorium turns forthwith. Many things are thereby seen to attract, both
those which are formed by nature alone, and those which are by art
prepared, fused, and mixed; nor is this so much a singular property of one
or two things (as is commonly supposed), but the manifest nature of very
many, both of simple substances, remaining merely in their own form, and of
compositions, as of hard sealing-wax, & of certain other mixtures besides,
made of unctuous stuffs. We must, however, investigate more fully whence
that tendency arises, and what those forces be, concerning which a few men
have brought forward very little, the crowd of philosophizers nothing at
all. By Galen three kinds of attractives in general were recognized in
nature: a First class of those substances which attract by their elemental
quality, namely, heat; the Second is the class of those which attract by
the succession of a vacuum; the Third is the class of those which attract
by a property of their whole substance, which are also quoted by Avicenna
and others. These classes, however, cannot in any way satisfy us; they
neither embrace the causes of amber, jet, and diamond, and of other similar
substances (which derive their forces on account of the same virtue); nor
of the loadstone, and of all magnetick substances, which obtain their
virtue by a very dissimilar and alien influence from them, derived from
other sources. Wherefore also it is fitting that we find other causes of
the motions, or else we must wander (as in darkness), with these men, and
in no way reach the goal. Amber truly does* not allure by heat, since if
warmed by fire and brought near straws, it does not attract them, whether
it be tepid, or hot, or glowing, or even when forced into the flame. Cardan
(as also Pictorio) reckons that this happens in no different way[129] than
with the cupping-glass, by the force of fire. Yet the attracting force of
the cupping-glass does not really come from the force of fire. But he had
previously said that the dry substance wished to imbibe fatty humour, and
therefore it was borne towards it. But these statements are at variance
with one another, and also foreign to reason. For if amber had moved
towards its food, or if other bodies had inclined towards amber as towards
provender, there would have been a diminution of the one which was
devoured, just as there would have been a growth of the other which was
sated. Then why should an attractive force of fire be looked for in amber?
If the attraction existed from heat, why should not very many other bodies
also attract, if warmed by fire, by the sun, or by friction? Neither can
the attraction be on account of the dissipating of the air, when it takes
place in open air (yet Lucretius the poet adduces this as the reason for
magnetical motions). Nor in the cupping-glass can heat or fire attract by
feeding on air: in the cupping-glass air, having been exhausted into flame,
{50} when it condenses again and is forced into a narrow space, makes the
skin and flesh rise in avoiding a vacuum. In the open air warm things
cannot attract, not metals even or stones, if they should * be strongly
incandescent by fire. For a rod of glowing iron, or a flame, or a candle,
or a blazing torch, or a live coal, when they are brought near to straws,
or to a versorium, do not attract; yet at the same time they manifestly
call in the air in succession; because they consume it, as lamps do oil.
But concerning heat, how it is reckoned by the crowd of philosophizers, in
natural philosophy and in _materia medica_ to exert an attraction otherwise
than nature allows, to which true attractions are falsely imputed, we will
discuss more at length elsewhere, when we shall determine what are the
properties of heat and cold. They are very general qualities or kinships of
a substance, and yet are not to be assigned as true causes, and, if I may
say so, those philosophizers utter some resounding words; but about the
thing itself prove nothing in particular. Nor does this attraction
accredited to amber arise from any singular quality of the substance or
kinship, since by more thorough research we find the same effect in very
many other bodies; and all bodies, moreover, of whatever quality, are
allured by all those bodies. Similarity also is not the cause; because all
things around us placed on this globe of the earth, similar and dissimilar,
are allured by amber and bodies of this kind; and on that account no cogent
analogy is to be drawn either from similarity or identity of substance. But
neither do similars mutually attract one another, as stone stone, flesh
flesh, nor aught else outside the class of magneticks and electricks.
Fracastorio would have it that "things which mutually attract one another
are similars, as being of the same species, either in action or in right
subjection. Right subjection is that from which is emitted the emanation
which attracts and which in mixtures often lies hidden on account of their
lack of form, by reason of which they are often different in act from what
they are in potency. Hence it may be that hairs and twigs move towards
amber and towards diamond, not because they are hairs, but because either
there is shut up in them air or some other principle, which is attracted in
the first place, and which bears some relation and analogy to that which
attracts of itself; in which diamond and amber agree through a principle
common to each." Thus far Fracastorio. Who if he had observed by a large
number of experiments that all bodies are drawn to electricks except those
which are aglow and aflame, and highly rarefied, would never have given a
thought to such things. It is easy for men of acute intellect, apart from
experiments and practice, to slip and err. In greater error do they remain
sunk who maintain these same substances to be not similar, but to be
substances near akin; and hold that on that account a thing moves towards
another, its like, by which it is brought to more perfection. But these are
{51} ill-considered views; for towards all electricks all things move[130]
except such as are aflame or are too highly rarefied, as air, which is the
universal effluvium of this globe and of the world. Vegetable substances
draw moisture by which their shoots are rejoiced and grow; from analogy
with that, however, Hippocrates, in his _De Natura Hominis_, Book I.,
wrongly concluded that the purging of morbid humour took place by the
specifick force of the drug. Concerning the action and potency of
purgatives we shall speak elsewhere. Wrongly also is attraction inferred in
other effects; as in the case of a flagon full of water, when buried in a
heap of wheat, although well stoppered, the moisture is drawn out; since
this moisture is rather resolved into vapour by the emanation of the
fermenting wheat, and the wheat imbibes the freed vapour. Nor do elephants'
tusks attract moisture, but drive it into vapour or absorb it. Thus then
very many things are said to attract, the reasons for whose energy must be
sought from other causes. Amber in a fairly large mass allures, if* it is
polished; in a smaller mass or less pure it seems not to attract without
friction. But very many electricks (as precious stones and some other
substances) do not attract at all unless rubbed. On the other hand many
gems, as well as other bodies, are polished, yet do* not allure, and by no
amount of friction are they aroused; thus the emerald, agate, carnelian,
pearls, jasper, chalcedony, alabaster, porphyry, coral, the marbles,
touchstone, flint, bloodstone, emery[131], do not acquire any power; nor do
bones, or ivory, or the hardest woods, as ebony, nor do cedar, juniper, or
cypress; nor do metals, silver, gold, brass, iron, nor any loadstone,
though many of them are finely polished and shine. But on the other hand
there are some other polished substances of which we have spoken before,
toward which, when they have been rubbed, bodies incline. This we shall
understand only when we have more closely looked into the prime origin of
bodies. It is plain to all, and all admit, that the mass of the earth, or
rather the structure and crust of the earth, consists of a twofold
material, namely, of fluid and humid matter, and of material of more
consistency and dry. From this twofold nature or the more simple compacting
of one, various substances take their rise among us, which originate in
greater proportion now from the earthy, now from the aqueous nature. Those
substances which have received their chief growth from moisture, whether
aqueous or fatty, or have taken on their form by a simpler compacting from
them, or have been compacted from these same materials in long ages, if
they have a sufficiently firm hardness, if rubbed after they have been
polished and when they remain bright with the friction--towards those
substances everything, if presented to them in the air, turns, if its too
heavy weight does not prevent it. For amber has been compacted of moisture,
and jet also. Lucid gems are made of water; just as Crystal[132], which has
been concreted from clear water, not {52} always by a very great cold, as
some used to judge, and by very hard frost, but sometimes by a less severe
one, the nature of the soil fashioning it, the humour or juices being shut
up in definite cavities, in the way in which spars are produced in mines.
So clear glass is fused out of sand, and from other substances, which have
their origin in humid juices. But the dross of metals, as also metals,
stones, rocks, woods, contain earth rather, or are mixed with a good deal
of earth; * and therefore they do not attract. Crystal, mica, glass, and
all electricks do not attract if they are burnt or roasted; for their
primordial supplies of moisture perish by heat, and are changed and
exhaled. All things therefore which have sprung from a predominant moisture
and are firmly concreted, and retain the appearance of spar and its
resplendent nature in a firm and compact body, allure all bodies, whether
humid or dry. Those, however, which partake of the true earth-substance or
are very little different from it, are seen to attract also, but from a far
different reason, and (so to say) magnetically; concerning these we intend
to speak afterwards. But those substances which are more mixed of water and
earth, and are produced by the equal degradation of each element (in which
the magnetick force of the earth is deformed and remains buried; while the
watery humour, being fouled by joining with a more plentiful supply of
earth, has not concreted in itself but is mingled with earthy matter), can
in no way of themselves attract or move from its place anything which they
do not touch. On this account metals, marbles, flints, woods, herbs, flesh,
and very many other things can neither allure nor solicit any body either
magnetically or electrically. (For it pleases us to call that an electrick
force, which hath * its origin from the humour.) But substances consisting
mostly of humour, and which are not very firmly compacted by nature
(whereby do they neither bear rubbing, but either melt down and become
soft, or are not levigable, such as pitch, the softer kinds of resin,
camphor, galbanum, ammoniack[133], storax, asafoetida, benzoin, asphaltum,
especially in rather warm weather) towards them small bodies are not borne;
for without rubbing most electricks do not * emit their peculiar and native
exhalation and effluvium. The resin turpentine when liquid does not
attract; for it cannot be rubbed; but if it has hardened into a mastick it
does attract. But now at length we must understand why small bodies turn
towards those substances which have drawn their origin from water; by what
force and with what hands (so to speak) electricks seize upon kindred
natures. In all bodies in the world two causes or principles have been laid
down, from which the bodies themselves were produced, matter and form[134].
Electrical motions become strong from matter, but magnetick from form
chiefly; and they differ widely from one another and turn out unlike, since
the one is ennobled by numerous virtues and is prepotent; the other is
ignoble and of less potency, and {53} mostly restrained, as it were, within
certain barriers; and therefore that force must at times be aroused by
attrition or friction, until it is at a dull heat and gives off an
effluvium and a polish is induced on the body. For spent air, either blown
out of the mouth or given* off from moister air, chokes the virtue. If
indeed either a sheet of paper or a piece of linen be interposed, there
will be no movement. But a loadstone, without friction or heat, whether dry
or suffused with moisture, as well in air as in water, invites magneticks,
even with the most solid bodies interposed, even planks of wood or pretty
thick slabs of stone or sheets of metal. A loadstone appeals to magneticks*
only; towards electricks all things move. A loadstone[135] raises great
weights; so that if there is a loadstone weighing two ounces and strong, it
attracts half an ounce or a whole ounce. An electrical substance only
attracts very small weights; as, for instance, a piece of amber of three
ounces weight, when rubbed, scarce raises a fourth part of a grain of
barley. But this attraction of amber and of electrical substances must be
further investigated; and since there is this particular affection of
matter, it may be asked why is amber rubbed, and what affection is produced
by the rubbing, and what causes arise which make it lay hold on everything?
As a result of friction it grows slightly warm and becomes smooth; two
results which must often occur together. A large polished fragment of amber
or jet attracts indeed, even without friction, but less strongly; but if it
be brought gently near a flame or a live coal, so that it equally becomes
warm, it does not attract small bodies because* it is enveloped in a cloud
from the body of the flaming substance, which emits a hot breath, and then
impinges upon it vapour from a foreign body which for the most part is at
variance with the nature of amber. Moreover the spirit of the amber which
is called forth is enfeebled by alien heat; wherefore it ought not to have
heat excepting that produced by motion only and friction, and, as it were,
its own, not sent into it by other bodies. For as the igneous heat emitted
from any burning substance cannot be so used that electricks may acquire
their force from it; so also heat from the solar rays does not fit an
electrick by the loosening of its* right material, because it dissipates
rather and consumes it (albeit a body which has been rubbed retains its
virtue longer exposed to the rays of the sun than in the shade; because in
the shade the effluvia are condensed to a greater degree and more quickly).
Then again the fervour from the light of the Sun aroused by means of a*
burning mirror confers no vigour on the heated amber[136]; indeed it
dissipates and corrupts all the electrick effluvia. Again, burning* sulphur
and hard wax, made from shell-lac, when aflame do not allure; for heat from
friction resolves bodies into effluvia, which flame consumes away. For it
is impossible for solid electricks to be resolved into their own true
effluvia otherwise than by attrition, save {54} in the case of certain
substances which by reason of innate vigour emit effluvia constantly. They
are rubbed with bodies which do not befoul their surface, and which produce
a polish, as pretty stiff silk or a rough wool rag which is as little
soiled as possible, or the dry palm. Amber also is rubbed with amber, with
diamond, and with glass, and numerous other substances. Thus are electricks
manipulated. These things being so, what is it which moves? Is it the body
itself, inclosed within its own circumference? Or is it something
imperceptible to us, which flows out from the substance into the ambient
air? Somewhat as Plutarch opines, saying in his _Quæstiones
Platonicæ_[137]: That there is in amber something flammable or something
having the nature of breath, and this by the attrition of the surface being
emitted from its relaxed pores attracts bodies. And if it be an effusion
does it seize upon the air whose motion the bodies follow, or upon the
bodies themselves? But if amber allured the body itself, then what need
were there of friction, if it is bare and smooth? Nor does the force arise
from the light which is reflected from a smooth and polished body; for a
Gem of Vincent's rock[138], Diamond, and clear glass, attract when they are
rough; but not so powerfully and quickly, because they are not so readily
cleansed from extraneous moisture on the surface, and are not rubbed
equally so as to be copiously resolved at that part. Nor does the sun by
its own beams of light and its rays, which are of capital importance in
nature, attract bodies in this way; and yet the herd of philosophizers
considers that humours are attracted by the sun, when it is only denser
humours that are being turned into thinner, into spirit and air; and so by
the motion of effusion they ascend into the upper regions, or the
attenuated exhalations are raised up from the denser air. Nor does it seem
to take place from the effluvia attenuating the air, so that bodies
impelled by the denser air penetrate towards the source of the rarefaction;
in this case both hot and flaming bodies would also allure other bodies;
but not even the lightest chaff, or any versorium moves towards a flame. If
there is a flow and rush of air towards the body, how can a small diamond
of the size of a pea[139] summon towards itself so much air, that it seizes
hold of a biggish long body placed in equilibrio (the air about one or
other very small part of an end being attracted)? It ought also to have
slopped or moved more slowly, before it came into contact with the body,
especially if the piece of amber was rather broad and flat, from the
accumulation of air on the surface of the amber and its flowing back again.
If it is because the effluvia are thinner, and denser vapours come in
return, as in breathing, then the body would rather have had a motion
toward the electrick a little while after the beginning of the application;
but when electricks which have been rubbed are applied quickly to * a
versorium then especially at once they act on the versorium, and it is
attracted more when near them. But if it is because the rarefied {55}
effluvia produce a rarefied medium, and on that account bodies are more
prone to slip down from a denser to a more attenuated medium; they might
have been carried from the side in this way or downwards, but not to bodies
above them; or the attraction and apprehension of contiguous bodies would
have been momentary only. But with a single friction jet and amber draw and
attract bodies to them strongly and for a long time, sometimes for the
twelfth part of an hour, especially in clear weather. But if the mass of
amber be rather large, and the surface polished, it attracts without
friction. Flint is rubbed and emits by attrition an inflammable matter that
turns into sparks and heat. Therefore the denser effluvia of flint
producing fire are very far different from electrical effluvia, which on
account of their extreme attenuation do not take fire, nor are fit material
for flame. Those effluvia are not of the nature of breath, for when emitted
they do not propel anything, but are exhaled without sensible resistance
and touch bodies. They are highly attenuated humours much more subtile than
the ambient air; and in order that they may occur, bodies are required
produced from humour and concreted with a considerable degree of hardness.
Non-electrick bodies are not resolved into humid effluvia, and those
effluvia mix with the common and general effluvia of the earth, and are not
peculiar. Also besides the attraction of bodies, they retain them longer.
It is probable therefore that amber does exhale something peculiar to *
itself, which allures bodies themselves, not the intermediate air. Indeed
it plainly does draw the body itself in the case of a spherical drop of
water standing on a dry surface; for a piece of amber applied to it at a
suitable distance pulls the nearest parts out of their position and draws
it up into a cone; otherwise, if it were * drawn by means of the air
rushing along, the whole drop would have moved. That it does not attract
the air is thus demonstrated: take a very thin wax candle, which makes a
very small and clear flame; bring up to this, within two digits or any
convenient distance, a piece of amber or jet, a broad flat piece, well
prepared * and skilfully rubbed, such a piece of amber as would attract
bodies far and wide, yet it does not disturb the flame; which of necessity
would have occurred, if the air was disturbed, for the flame would have
followed the current of air. As far as the effluvia are sent out, so far it
allures; but as a body approaches, its motion is accelerated, stronger
forces drawing it; as also in the case of magneticks and in all natural
motion; not by attenuating or by expelling the air, so that the body moves
down into the place of the air which has gone out[140]; for thus it would
have allured only and would not have retained; since it would at first also
have repelled approaching bodies just as it drives the air itself; but
indeed a particle, be it ever so small, does not avoid the first
application made very quickly after rubbing. An effluvium exhales from
amber and is emitted by rubbing: pearls, carnelian, agate, jasper,
chalcedony, coral, metals, {56} and other substances of that kind, when
they are rubbed, produce no effect. Is there not also something which is
exhaled from them by heat and attrition? Most truly; but from grosser
bodies more blended with the earthy nature, that which is exhaled is gross
and spent; for even towards very many electricks, if they are rubbed * too
hard, there is produced but a weak attraction of bodies, or none at all;
the attraction is best when the rubbing has been gentle and very quick; for
so the finest effluvia are evoked. The effluvia arise from the subtile
diffusion of humour, not from excessive and turbulent violence; especially
in the case of those substances which have been compacted from unctuous
matter, which when the atmosphere is very thin, when the North winds, and
amongst us (English) the East winds, are blowing, have a surer and firmer
effect, but during South winds and in damp weather, only a weak one; so
that those * substances which attract with difficulty in clear weather, in
thick weather produce no motion at all; both because in grosser air lighter
substances move with greater difficulty; and especially because the
effluvia are stifled, and the surface of the body that has been rubbed is
affected by the spent humour of the air, and the effluvia are stopped at
their very starting. On that account in the case of amber, jet, and
sulphur, because they do not so easily take up moist air on their surface
and are much more plenteously set free, that force is not so quickly
suppressed as in gems, crystal, glass, and substances of that kind which
collect on their surface the moister breath which has grown heavy. But it
may be asked why does amber allure water, when water placed on its surface
removes its action? Evidently because it is one thing to suppress it at its
very start, and quite another to extinguish it when it has been * emitted.
So also thin and very fine silk, in common language _Sarcenet_, placed
quickly on the amber, after it has been rubbed, * hinders the attraction of
the body; but if it is interposed in the intervening space, it does not
entirely obstruct it. Moisture also from spent air, and any breath blown
from the mouth, as well as water put on the amber, immediately extinguishes
its force. But oil, which is light and pure, does not hinder it; for
although amber * be rubbed with a warm finger dipped in oil, still it
attracts. But * if that amber, after the rubbing, is moistened with _aqua
vitæ_ or spirits of wine, it does not attract; for it is heavier than oil,
denser, and when added to oil sinks beneath it. For oil is light and rare,
and does not resist the most delicate effluvia. A breath therefore,
proceeding from a body which had been compacted from humour or from a
watery liquid, reaches the body to be attracted; the body that is reached
is united with the attracting body, and the one body lying near the other
within the peculiar radius of its effluvia makes one out of two; united,
they come together into the closest accord, and this is commonly called
attraction. This unity, according to {57} the opinion of Pythagoras, is the
principle of all things, and through participation in it each several thing
is said to be one. For since no action can take place by means of matter
unless by contact, these electricks are not seen to touch, but, as was
necessary, something is sent from the one to the other, something which may
touch closely and be the beginning of that incitement. All bodies are
united and, as it were, cemented together in some way by moisture; so that
a wet body, when it touches another body, attracts it, if it is small. So
wet bodies on the surface of water attract wet bodies. But the peculiar
electrical effluvia, which are the most subtile material of diffuse humour,
entice corpuscles. Air (the common effluvium of the earth) not only unites
the disjointed parts, but the earth calls bodies back to itself by means of
the intervening air; otherwise bodies which are in higher places would not
so eagerly make for the earth. Electrical effluvia differ greatly from air;
and as air is the effluvium of the earth, so electricks have their own
effluvia and properties, each of them having by reason of its peculiar
effluvia a singular tendency toward unity, a motion toward its origin and
fount, and toward the body emitting the effluvia. But those substances
which by attrition emit a gross or vapourous or aeriform effluvium produce
no effect; for either such effluvia are alien to the humour (the uniter of
all things), or being very like common air are blended with the air and
intermingle with the air, wherefore they produce no effect in the air, and
do not cause motions different from those so universal and common in
nature. In like manner * bodies strive to be united and move on the surface
of water, just [Illustration] as the rod C, which is put a little way under
water. It is plain that the rod E F, which floats on the water by reason of
the cork H, and only has its wet end F above the surface of the water, is
attracted by the rod C, if the rod C is wet a little above the surface of
the water; they are suddenly united, just as a drop adjoining a drop is
attracted. So a wet thing on the surface of water seeks union with a wet
thing, since the surface of the water is raised on both; and they
immediately flow together, just like drops or bubbles. But they are in much
greater proximity than electricks, and are united by their clammy natures.
If, however, the whole rod be dry * above the water, it no longer attracts,
but drives away the stick E F. The same is seen in those bubbles also which
are made on {58} water. For we see one drive towards another, and the
quicker the nearer they are. Solids are impelled towards solids by the
medium of liquid: for example, touch the end of a versorium with the end of
a rod on which a drop of water is projecting; as soon as the versorium
touches the top of the droplet, immediately it is joined * strongly by a
swift motion to the body of the rod. So concreted humid things attract when
a little resolved into air (the effluvia in the intermediate space tending
to produce unity); for water has on wet bodies, or on bodies wet with
abundant moisture on the top of water, the force of an effluvium. Clear air
is a convenient medium for an electrical effluvium excited from concreted
humour. Wet bodies projecting above the surface of water (if they are near)
run together so that they may unite; for the surface of the water is raised
around wet substances. But a dry thing is not impelled to a wet one, nor a
wet to a dry, but seems to run away. For if all is dry above the water, the
surface of the water close to it does not rise, but shuns it, the wave
sinking around a dry thing. So neither does a wet thing move towards the
dry rim of a vessel; but it seeks [Illustration] a wet rim. A B is the
surface of the water; C D two rods, which stand up wet above the water; it
is manifest that the surface of the water is raised at C and D along with
the rods; and therefore the rod C, by reason of the water standing up
(which seeks its level and unity), moves with the water to D. On E, on the
other hand, a wet rod, the water also rises; but on the dry rod F the
surface is depressed; and as it drives to depress also the wave rising on E
in its neighbourhood, the higher wave at E turns away from F[141]; for it
does not suffer itself to be depressed. All electrical attraction occurs
through an intervening humour; so it is by reason of humour that all things
mutually come together; fluids indeed and aqueous bodies on the surface of
water, but concreted things, if they have been resolved into vapour, in
air;--in air indeed, the effluvium of electricks being very rare, that it
may the better permeate the medium and not impel it by its motion; for if
that effluvium had been thick, as that of air, or of the winds, or of
saltpetre burnt by fire, as the thick and foul effluvia given out with very
great force, from other bodies, or air set free from humour by heat rushing
out through a pipe (in the instrument of Hero of Alexandria, described in
his {59} book _Spiritalia_), then the effluvium would drive everything
away, not allure it. But those rarer effluvia take hold of bodies and
embrace them as if with arms extended, with the electricks to which they
are united; and they are drawn to the source, the effluvia increasing in
strength with the proximity. But what is that effluvium from crystal,
glass, and diamond, since these are bodies of considerable hardness and
firmly concreted? In order that such an effluvium should be produced, there
is no need of any marked or perceptible flux[142] of the substance; nor is
it necessary that the electrick should be abraded, or worn away, or
deformed. Some odoriferous substances are fragrant for many years, exhaling
continually, yet are not quickly consumed. Cypress wood as long as it is
sound, and it lasts a very long time indeed, is redolent; as many learned
men attest from experience. Such an electrick only for a moment, when
stimulated by friction, emits powers far more subtile and more fine beyond
all odours; yet sometimes amber, jet, sulphur, when they are somewhat
easily let free into vapour, also pour out at the same time an odour; and
on this account they allure with the very gentlest rubbing, often even
without rubbing; they also excite more strongly, and retain hold for a
longer time, because they have stronger effluvia and last longer. But
diamond, glass, rock-crystal, * and numerous others of the harder and
firmly concreted gems first grow warm: therefore at first they are rubbed
longer, and then they also attract strongly; nor are they otherwise set
free into vapour. Everything rushes towards electricks[143] excepting
flame, and flaming bodies, and the thinnest air. Just as they do not draw
flame, in like manner they do not affect a versorium, if on any side it is
very near to a flame, either the flame of a lamp or of any burning matter.
It is manifest indeed that the effluvia are destroyed by flame and igneous
* heat; and therefore they attract neither flame nor bodies very near a
flame. For electrical effluvia have the virtue of, and are analogous with,
extenuated humour; but they will produce their effect, union and
continuity, not by the external impulse of vapours, not by heat and
attenuation of heated bodies, but by their humidity itself attenuated into
its own peculiar effluvia. Yet they entice * smoke sent out by an
extinguished light; and the more that smoke is attenuated in seeking the
upper regions, the less strongly is it turned aside; for things that are
too rarefied are not drawn to them; and at length, when it has now almost
vanished, it does not * incline towards them at all, which is easily seen
against the light. When in fact the smoke has passed into air, it is not
moved, as has been demonstrated before. For air itself, if somewhat thin,
is not attracted in any way, unless on account of succeeding that which has
vacated its place, as in furnaces and such-like, where the air is fed in by
mechanical devices for drawing it in. Therefore an effluvium resulting from
a non-fouling friction, and one which {60} is not changed by heat, but
which is its own, causes union and coherency, a prehension and a congruence
towards its source, if only the body to be attracted is not unfitted for
motion, either by the surroundings of the bodies or by its own weight. To
the bodies therefore of the electricks themselves small bodies are borne.
The effluvia extend out their virtue--effluvia which are proper and
peculiar to them, and _sui generis_, differing from common air, being
produced from humour, excited by a calorifick motion from attrition and
attenuation. And as if they were material rays[144], they hold and take up
chaff, straws, and twigs, until they become extinct or vanish away: and
then they (the corpuscles) being loosed again, attracted by the earth
itself, fall down to the earth. The difference between Magneticks and
Electricks[145] is that all magneticks run together with mutual forces;
electricks only allure; that which is allured is not changed by an
implanted force, but that which has moved up to * them voluntarily rests
upon them by the law of matter. Bodies are borne towards electricks in a
straight line towards the centre of the electrick; a loadstone draws a
loadstone directly at the poles only, in other parts obliquely and
transversely, and in this way also they adhere and hang to one another.
Electrical motion is a motion of aggregation of matter; magnetical motion
is one of disposition and conformation. The globe of the earth is
aggregated and cohæres by itself electrically. The globe of the earth is
directed and turned magnetically; at the same time also it both cohæres,
and in order that it may be solid, is in its inmost parts cemented
together.
* * * * *
CHAP. III.
Opinions of others on Magnetick Coition,
_which they call Attraction_.
Discussion having now been made concerning electricks, the causes of
magnetick coition must be set forth. We say coition, not attraction[146].
The word attraction unfortunately crept into magnetick philosophy from the
ignorance of the ancients; for there seems to be force applied where there
is attraction and an imperious violence dominates. For, if ever there is
talk about magnetick attraction, we understand thereby magnetick coition,
or a primary running together. Now in truth it will not be useless here
first briefly to set forth the views given by others, both the ancient {61}
and the more modern writers. Orpheus in his hymns[147] narrates that iron
is attracted by loadstone as the bride to the arms of her espoused.
Epicurus holds that iron is attracted by a loadstone just as straws by
amber; "and," he adds, "the Atoms and indivisible particles which are given
off by the stone and by the iron fit one another in shape; so that they
easily cling to one another; when therefore these solid particles of stone
or of iron strike against one another, then they rebound into space, being
brought against one another by the way, and they draw the iron along with
them." But this cannot be the case in the least; since solid and very dense
substances interposed, even squared blocks of marble, do not obstruct this
power, though they can separate atoms from atoms; and the stone and the
iron would be speedily dissipated into such profuse and perpetual streams
of atoms. In the case of amber, since there is another different method of
attracting, the Epicurean atoms cannot fit one another in shape. Thales, as
Aristotle writes, _De Anima_, Bk. I., deemed the loadstone to be endowed
with a soul of some sort, because it had the power of moving and drawing
iron towards it. Anaxagoras also held the same view. In the _Timæus_ of
Plato there is an idle fancy[148] about the efficacy of the stone of
Hercules. For he says that "all flowings of water, likewise the fallings of
thunderbolts, and the things which are held wonderful in the attraction of
Amber, and of the Herculean stone, are such that in all these there is
never any attraction; but since there is no vacuum, the particles drive one
another mutually around, and when they are dispersed and congregated
together, they all pass, each to its proper seat, but with changed places;
and it is forsooth, on account of these intercomplicated affections that
the effects seem to arouse the wonder in him who has rightly investigated
them." Galen does not know why Plato should have seen fit to select the
theory of circumpulsion rather than that of attraction (differing almost on
this point alone from Hippocrates), though indeed it does not agree in
reality with either reason or experiment. Nor indeed is either the air or
anything else circumpelled; and the bodies themselves which are attracted
are carried towards the attracting substance not confusedly, or in an orbe.
Lucretius, the poet of the Epicurean sect, sang his opinion of it thus:
[149]_First, then, know,_
_Ceaseless effluvia from the magnet flow,--_
_Effluvia, whose superior powers expel_
_The air that lies between the stone and steel._
_A vacuum formed, the steely atoms fly_
_In a link'd train, and all the void supply;_
_While the whole ring to which the train is join'd_
_The influence owns, and follows close behind. &c._
{62} Such a reason Plutarch also alleges in the _Quæstiones Platonicæ_:
That that stone gives off heavy exhalations, whereby the adjacent air,
being impelled along, condenses that which is in front of it; and that air,
being driven round in an orbe and reverting to the place it had vacated,
drags the iron forcibly along with it. The following explanation of the
virtues of the loadstone and of amber is propounded by Johannes Costæus of
Lodi[150]. For he would have it that "there is mutual work and mutual
result, and therefore the motion is partly due to the attraction of the
loadstone and partly to a spontaneous movement on the part of the iron: For
as we say that vapours issuing from the loadstone hasten by their own
nature to attract the iron, so also the air repelled by the vapours, whilst
seeking a place for itself, is turned back, and when turned back, it impels
the iron, lifts it up, as it were, and carries it along; the iron being of
itself also excited somehow. So by being drawn out and by a spontaneous
motion, and by striking against another substance, there is in some way
produced a composite motion, which motion would nevertheless be rightly
referred to attraction, because the terminus from which this motion
invariably begins is the same terminus at which it ends, which is the
characteristic proper of an attraction." There is certainly a mutual
action, not an operation, nor does the loadstone attract in that way; nor
is there any impulsion. But neither is there that origination of the motion
by the vapours, and the turning of them back, which opinion of Epicurus has
so often been quoted by others. Galen errs in his _De Naturalibus
Facultatibus_, Book I., chap. 14, when he expresses the view that whatever
agents draw out either the venom of serpents or darts also exhibit the same
power as the loadstone. Now of what sort may be the attraction of such
medicaments (if indeed it may be called attraction) we shall consider
elsewhere. Drugs against poisons or darts have no relation to, no
similitude with, the action of magnetical bodies. The followers of Galen
(who hold that purgative medicaments attract because of similitude of
substance) say that bodies are attracted on account of similitude, not
identity, of substance; wherefore the loadstone draws iron, but iron does
not draw iron. But we declare and prove that this happens in primary
bodies, and in those bodies that are pretty closely related to them and
especially like in kind one to another, on account of their identity;
wherefore also loadstone draws loadstone and likewise iron iron; every
really true earth draws earth; and iron fortified by a loadstone within the
orbe of whose virtue it is placed draws iron more strongly than it does the
loadstone. Cardan asks why no other metal is attracted by any other stone;
because (he replies) no metal is so cold as iron; as if indeed cold were
the cause of the attraction, or as if iron were much colder than lead,
which neither follows nor is deflected towards a loadstone. {63} But that
is a chilly story, and worse than an old woman's tale. So also is the
notion that the loadstone is alive and that iron is its food. But how does
the loadstone feed on the iron, when the filings in which it is kept are
neither consumed nor become lighter? Cornelius Gemma, _Cosmographia_, Bk.
X.[151], holds that the loadstone draws iron to it by insensible rays, to
which opinion he conjoins a story of a sucking fish and another about an
antelope. Guilielmus Puteanus[152] derives it, "not from any property of
the whole substance unknown to any one and which cannot be demonstrated in
any way (as Galen, and after him almost all the physicians, have asserted),
but from the essential nature of the thing itself, as if moving from the
first by itself, and, as it were, by its own most powerful nature and from
that innate temperament, as it were an instrument, which its substance, its
effective nature uses in its operations, or a secondary cause and deprived
of its intermediary"; so the loadstone attracts the iron not without a
physical cause and for the sake of some good. But there is no such thing in
other substances springing from some material form; unless it were primary,
which he does not recognize. But certes good is shown to the loadstone by
the stroke of the iron (as it were, association with a friend); yet it
cannot either be discovered or conceived how that disposition may be the
instrument of form. For what can temperament do in magnetical motions,
which must be compared with the fixed, definite, constant motions of the
stars, at great distances in case of the interposition of very dense and
thick bodies? To Baptista Porta[153] the loadstone seems a sort of mixture
of stone and iron, in such a way that it is an iron stone or stony iron.
"But I think" (he says) "the Loadstone is a mixture of stone and iron, as
an iron stone, or a stone of iron. Yet do not think the stone is so changed
into iron, as to lose its own Nature, nor that the iron is so drowned in
the stone, but it preserves itself; and whilst one labours to get the
victory of the other, the attraction is made by the combat between them. In
that body there is more of the stone than of iron; and therefore the iron,
that it may not be subdued by the stone, desires the force and company of
iron; that being not able to resist alone, it may be able by more help to
defend itself.... The Loadstone draws not stones, because it wants them
not, for there is stone enough in the body of it; and if one Loadstone draw
another, it is not for the stone, but for the iron that is in it." As if in
the loadstone the iron were a distinct body and not mixed up as the other
metals in their ores! And that these, being so mixed up, should fight with
one another, and should extend their quarrel, and that in consequence of
the battle auxiliary forces should be called in, is indeed absurd. But iron
itself, when excited by a loadstone, seizes iron no less strongly than the
loadstone. Therefore those fights, seditions, and conspiracies in the
stone, as if it were nursing up perpetual quarrels, {64} whence it might
seek auxiliary forces, are the ravings of a babbling old woman, not the
inventions of a distinguished mage. Others have lit upon sympathy as the
cause. There may be fellow-feeling, and yet the cause is not
fellow-feeling; for no passion can rightly be said to be an efficient
cause. Others hold likeness of substance, many others insensible rays as
the cause; men who also in very many cases often wretchedly misuse rays,
which were first introduced in the natural sciences by the mathematicians.
More eruditely does Scaliger[154] say that the iron moves toward the
loadstone as if toward its parent, by whose secret principles it may be
perfected, just as the earth toward its centre. The Divine Thomas[155] does
not differ much from him, when in the 7th book of his _Physica_ he
discusses the reasons of motions. "In another way," he says, "it may be
said to attract a thing, because it moves it to itself by altering it in
some way, from which alteration it happens that when altered it moves
according to its position, and in this manner the loadstone is said to
attract iron. For as the parent moves things whether heavy or light, in as
far as it gives them a form, by means of which they are moved to their
place; so also the loadstone gives a certain quality to the iron, in
accordance with which it moves towards it." This by no means ill-conceived
opinion this most learned man shortly afterwards endeavoured to confirm by
things which had obtained little credence respecting the loadstone and the
adverse forces of garlick. Cardinal Cusan[156] also is not to be despised.
"Iron has," he says, "in the loadstone a certain principle of its own
effluence; and whilst the loadstone by its own presence excites the heavy
and ponderous iron, the iron is borne by a wonderful yearning, even above
the motion of nature (by which in accordance with its weight it ought to
tend downwards) and moves upwards, in uniting itself with its own
principle. For if there were not in the iron a certain natural foretaste of
the loadstone itself, it would not move to the loadstone any more than to
any other stone; and unless there were in the stone a greater inclination
for iron than for copper, there would not be that attraction." Such are the
opinions expressed about the loadstone attracting (or the general sense of
each), all dubious and untrustworthy. But those causes of the magnetical
motions, which in the schools of the Philosophers are referred to the four
elements and the prime qualities, we relinquish to the moths and the worms.
* * * * *
{65} CHAP. IIII.
On Magnetick Force & Form, what it is; and on the
_cause of the Coition_.
Relinquishing the opinions of others on the attraction of loadstone, we
shall now show the reason of that coition and the translatory nature of
that motion. Since there are really two kinds of bodies, which seem to
allure bodies with motions manifest to our senses, Electricks and
Magneticks, the Electricks produce the tendency by natural effluvia from
humour; the Magneticks by agencies due to form, or rather by the prime
forces. This form is unique, and particular, not the formal cause of the
Peripateticks, or the specifick in mixtures, or the secondary form; not the
propagator of generating bodies, but the form of the primary and chief
spheres and of those parts of them which are homogeneous and not corrupted,
a special entity and existence, which we may call a primary and radical and
astral form; not the primary form of Aristotle, but that unique form, which
preserves and disposes its own proper sphere. There is one such in each
several globe, in the Sun, the moon, and the stars; one also in the earth,
which is that true magnetick potency which we call the primary vigour.
Wherefore there is a magnetick nature peculiar to the earth and implanted
in all its truer parts in a primary and astonishing manner; this is neither
derived nor produced from the whole heaven by sympathy or influence or more
occult qualities, nor from any particular star; for there is in the earth a
magnetick vigour of its own, just as in the sun and moon there are forms of
their own, and a small portion of the moon settles itself in moon-manner
toward its termini and form; and a piece of the sun to the sun, just as a
loadstone to the earth and to a second loadstone by inclining itself and
alluring in accordance with its nature. We must consider therefore about
the earth what magnetical bodies are, and what is a magnet; then also about
the truer parts of it, which are magnetical, and how they are affected as a
result of the coition. A body which is attracted by an electrick is not
changed by it, but remains unshaken and unchanged, as it was before, nor
does it excel any the more in virtue. A loadstone draws magnetical
substances, which eagerly acquire power from its strength, not in their
extremities only, but in their inward parts and * their very marrow. For
when a rod of iron is laid hold of, it is magnetically excited in the end
by which it is laid hold of, and that {66} force penetrates even to the
other extremity, not through its surface only, but through the interior and
all through the middle. Electrical bodies have material and corporeal
effluvia. Is any such magnetical effluvium given off, whether corporeal or
incorporeal? or is nothing at all given off that subsists? If it really has
a body, that body must be thin and spiritual, since it is necessary that it
should be able to enter into iron. Or what sort of an exhalation is it that
comes from lead, when quicksilver which is bright and fluid is bound
together by the odour merely and vapour of the lead, and remains, as it
were, a firm metal? But even gold, which is exceedingly solid and dense, is
reduced to a powder by the thin vapour of lead. Or, seeing that, as the
quicksilver has entrance into gold, so the magnetical odour has entrance
into the substance of the iron, how does it change it in its essential
property, although no change is perceptible to our senses in the bodies
themselves? For without ingression into the body, the body is not changed,
as the Chemists not incorrectly teach. But if indeed these things resulted
from a material ingression, then if strong and dense and thick substances
had been interposed between the bodies, or if magnetical substances had
been inclosed in the centres of the most solid and the densest bodies, the
iron particles would not have suffered anything from the loadstone. But
none the less they strive to come together and are changed. Therefore there
is no such conception and origin of the magnetick powers; nor do the very
minute portions of the stone exist, which have been wrongly imagined to
exist by Baptista Porta, aggregated, as it were, into hairs, and arising
from the rubbing of the stone which, sticking to the iron, constitute its
strength. Electrick effluvia are not only impeded by any dense matter, but
also in like manner by flames, or if a small flame is near, they do not
allure. But as iron is not hindered by any obstacle from receiving force or
motion from a loadstone, so it will pass through the midst of flames to the
body of the loadstone and adhære to the stone. Let there be a flame or a
candle near the stone; bring up a short piece of iron wire, and when it has
come near, it will penetrate through the midst of the flames to the stone;
* and a versorium turns towards the loadstone nor more slowly nor less
eagerly through the midst of flames than through open air. So flames
interposed do not hinder the coition. But if the iron itself became heated
by a great heat, it is demonstrable that it would not be attracted. Bring a
strongly ignited rod of iron near a magnetized versorium; the versorium
remains steady and does not turn towards * such iron; but it immediately
turns towards it, so soon as it has lost somewhat of its heat. When a piece
of iron has been touched by a loadstone, if it be placed in a hot fire
until it is perfectly red hot * and remain in the fire some considerable
time, it will lose that magnetick strength it had acquired. Even a
loadstone itself through a {67} longish stay in the fire, loses the powers
of attracting implanted and innate in it, and any other magnetick powers.
And although certain veins of loadstone exhale when burnt a dark vapour of
a black colour, or of a sulphurous foul odour, yet that vapour was not the
soul, or the cause of its attraction of iron (as Porta thinks), nor do all
loadstones whilst they are being baked or burnt smell of or exhale sulphur.
It is acquired as a sort of inborn defect from a rather impure mine or
matrix. Nor does anything analogous penetrate into the iron from that
material corporeal cause, since the iron conceives the power of attracting
and verticity from the loadstone, even if glass or gold or any other stone
be interposed. Then also cast iron acquires the power of attracting iron,
and verticity, from the verticity of the earth, as we shall afterwards
plainly demonstrate in _Direction_. But fire destroys the magnetick virtues
in a stone, not because it takes away any parts specially attractive, but
because the consuming force of the flame mars by the demolition of the
material the form of the whole; as in the human body the primary faculties
of the soul are not burnt, but the charred body remains without faculties.
The iron indeed may remain after the burning is completed and is not
changed into ash or slag; nevertheless (as Cardan not inaptly says) burnt
iron is not iron, but something placed outside its nature until it is
reduced. For just as by the rigour of the surrounding air[157] water is
changed from its nature into ice; so iron, glowing in fire, is destroyed by
the violent heat, and has its nature confused and perturbed; wherefore also
it is not attracted by a loadstone, and even loses that power of attracting
in whatever way acquired, and acquires another verticity when, being, as it
were, born again, it is impregnated by a loadstone or the earth, or when
its form is revived, not having been dead but confused, concerning which
many things are manifest in the change of verticity. Wherefore
Fracastorio[158] does not confirm his opinion, that the iron is not
altered; "for if it were altered," he says, "by the form of the loadstone,
the form of the iron would have been spoiled." This alteration is not
generation, but the restitution and reformation of a confused form. There
is not therefore anything corporeal which comes from the loadstone or which
enters the iron, or which is sent back from the iron when it is stimulated;
but loadstone disposes loadstone by its primary form; iron, however, which
is closely related to it, loadstone at the same time recalls to its
conformate strength, and settles it; on account of which it rushes to the
loadstone and eagerly conforms itself to it (the forces of each in harmony
bringing them together). The coition also is not vague or confused, not a
violent inclination of body to body, no rash and mad congruency; no
violence is here applied to the bodies; there are no strifes or discords;
but there is that concord (without which the universe would go to pieces),
that analogy, namely, of the {68} perfect and homogeneous parts of the
spheres of the universe to the whole, and a mutual concurrency of the
principal forces in them, tending to soundness, continuity, position,
direction, and to unity. Wherefore in the case of such wonderful action and
such a stupendous implanted vigour (diverse from other natures) the opinion
of Thales of Miletus[159] was not very absurd, nor was it downright
madness, in the judgment of Scaliger, for him to grant the loadstone a
soul; for the loadstone is incited, directed, and orbitally moved by this
force, which is all in all, and, as will be made clear afterwards, all in
every part; and it seems to be very like a soul. For the power of moving
itself seems to point to a soul; and the supernal bodies, which are also
celestial, divine, as it were, are thought by some to be animated, because
they move with admirable order. If two loadstones be set one over against
the other, each in a boat, on the surface of water, they do not immediately
run together, but first they turn towards one another, or the lesser
conforms to the greater, by moving itself in a somewhat circular manner,
and at length, when they are disposed according to their nature, they run
together. In smelted iron which has not been excited by a magnet there is
no need for such an apparatus; since it has no verticity, excepting what is
adventitious and acquired, and that not stable and confirmed (as is the
case with loadstone, even if the iron has been smelted from the best
loadstone), on account of the confusion of the parts by fire when it flowed
as a liquid; it suddenly acquires polarity and natural aptitude by the
presence of the loadstone, by a powerful mutation, and by a conversion into
a perfect magnet, and by an absolute metamorphosis; and it flies to the
body of the magnet as if it were a real piece of loadstone. For a loadstone
has no power, nor can a perfect loadstone do anything which iron when
excited by loadstone cannot perform, even when it has not been touched but
only placed in its vicinity. For when first it is within the orbe of virtue
of the loadstone, though it may be some distance away, yet it is
immediately changed, and has a renovated form, formerly indeed dormant and
inert in body, now lively and strong, which will be clearly apparent in the
demonstrations of _Direction_. So the magnetick coition is a motion of the
loadstone and of the iron, not an action of one[160]; an [Greek:
entelecheia], of each, not [Greek: ergon]; a [Greek: sunentelecheia] or
conjoint action, rather than a sympathy. There is properly no such thing as
magnetick antipathy. For the flight and declination of the ends, or an
entire turning about, is an action of each towards unity by the conjoint
action and [Greek: sunentelecheia] of both. It has therefore newly put on
the form, and on account of this being roused, it then, in order that it
may more surely acquire it, rushes headlong on the loadstone, not with
curves and turnings, as a loadstone to a loadstone. For since in a
loadstone both verticity and the power disponent have existed through many
ages, or from the very beginnings, {69} have been inborn and confirmed, and
also the special form of the terrestrial globe cannot easily be changed by
another loadstone, as iron is changed; it happens from the constant nature
of each, that one has not the sudden power over another of changing its
verticity, but that they can only mutually come to agreement with each
other. Again, iron which has been excited by a loadstone, * if that iron on
account of obstacles should not be able to turn round immediately in
accordance with its nature, as happens with a versorium, is laid hold of,
when a loadstone approaches, on either side or at either end. Because, just
as it can implant, so it can suddenly change the polarity and turn about
the formal energies to any part whatever. So variously can iron be
transformed when its form is adventitious and has not yet been long
resident in the metal. In the case of iron, on account of the fusion of the
substance when magnetick ore or iron is smelted, the virtue of its primary
form, distinct before, is now confused; but an entire loadstone placed near
it again sets up its primal activity; its adjusted and arranged form joins
its allied strength with the loadstone; and both mutually agree and are
leagued together magnetically in all their motions towards unity, and
whether joined by bodily contact or adjusted within the orbe, they are one
and the same. For when iron is smelted out of its own ore, or steel (the
more noble kind of iron) out of its ore, that is, out of loadstone, the
material is loosed by the force of the fire, and flows away, and iron as
well as steel flow out from their dross and are separated from it; and the
dross is either spoiled by the force of the fire and rendered useless, or
is a kind of dregs of a certain imperfection and of mixture in the
prominent parts of the earth. The material therefore is a purified one, in
which the metallick parts, which are now mixed up by the melting, since
those special forces of its form are confused and uncertain, by the
approach of a loadstone are called back to life, as if to a kind of
disponent form and integrity. The material is thus awakened and moves
together into unity, the bond of the universe and the essential for its
conservation. On this account and by the purging of the material into a
cleaner body, the loadstone gives to the iron a greater force of attracting
than there is in itself. For if iron dust * or an iron nail be placed over
a large loadstone, a piece of iron joined to it takes away the filings and
nail from the loadstone and retains them so long as it is near the
loadstone; wherefore iron attracts iron more than loadstone does, if it
have been conformed by a loadstone and remains within the orbe of its
communicated form. A piece of iron even, skilfully placed near the pole of
a loadstone, lifts up more than the loadstone. Therefore the material of
its own ore is better, and by the force of fire steel and iron are
re-purged; and they are again impregnated by the loadstone with its own
forms; therefore they move towards it by a spontaneous {70} approach as
soon as they have entered within the orbe of the magnetick forces, because
they were possessed by it before, connected and united with it in a perfect
union; & they have immediately an absolute continuity within that orbe, &
have been joined on account of their harmony, though their bodies may have
been disjoined. For the iron is not taken possession of and allured by
material effluvia, after the manner of electricks, but only by the
immaterial action of its form or an incorporeal progression, which in a
piece of iron as its subject acts and is conceived, as it were, in a
continuous homogeneous body, and does not need more open ways. Therefore
(though the most solid substances be interposed) the iron is still moved
and attracted, and by the presence of loadstone the iron moves and attracts
the loadstone itself, and by mutual forces a concurrency is made towards
unity, which is commonly called attraction of the iron. But those formal
forces pass out and are united to one another by meeting together; a force
also, when conceived in the iron, begins to flow out without delay. But
Julius Scaliger, who by other examples contends that this theory is absurd,
makes in his 344th Exercise a great mistake. For the virtues of primary
bodies are not to be compared with bodies formed from and mixed with them.
He would now have been able (had he been still alive) to discern the nature
of effused forms in the chapter on forms effused by spherical magneticks.
But if iron is injured somewhat by rust, it is affected either only
slightly or not at all by the stone. For the metal is spoiled when eaten
away and deformed by external injuries or by lapse of time (just as has
been said about the loadstone), and it loses its prime qualities which are
conjoined to its form; or, being worn out by age, retains them in a languid
and weak condition; indeed it cannot be properly re-formed, when it has
been corrupted. But a powerful and fresh loadstone attracts sound and clean
pieces of iron, and those pieces of iron (when they have conceived
strength) have a powerful attraction for other iron wires and iron nails,
not only one at a time, but even successively one behind another, three,
four or five, end to end, sticking and hanging in order like a chain. The
loadstone, however, would not attract the last one following in such a row,
if there were no nails between. [Illustration] A loadstone placed as at A
draws a nail or a bar B; similarly behind B it draws C; and after C, D. But
the nails B and C being removed, the loadstone A, if it remain at the same
distance, does not raise the nail D into the air. This occurs for this
reason: because in the case of a continuous row of nails the presence of
the loadstone A, besides its own powers, raises the magnetick natures of
the iron works B and C, and makes them, as it were, forces auxiliary to
itself. But B and C, like a continuous magnetical body, extend as far as
{71} D the forces by which D is taken and conformed, though they are weaker
than those which C receives from B. And those iron nails indeed from that
contact only, and from the presence of the loadstone even without contact,
acquire powers which they retain in their own bodies, as will be
demonstrated most clearly in the passage _on Direction_. For not only
whilst the stone is present does the iron assume these powers, and take
them, as it were, vicariously from the stone, as Themistius lays down in
his 8th book on Physicks[161]. The best iron, when it has been melted down
(such is steel), is allured by a loadstone from a greater distance, is
raised though of greater weight, is held more firmly, assumes stronger
powers than the common and less expensive, because it is cast from a better
ore or loadstone, imbued with better powers. But what is made from more
impure ore turns out weaker and is moved more feebly. As to
Fracastorio's[162] statement that he saw a piece of loadstone draw a
loadstone by one of its faces, but not iron; by another face iron, but not
loadstone; by another both; which he says is an indication that in one part
there is more of the loadstone, in another more of the iron, in another
both equally, whence arises that diversity of attraction; it is most
incorrect and badly observed on the part of Fracastorio, who did not know
how to apply skilfully loadstone to loadstone. A loadstone draws iron and
also a loadstone, if both are suitably arranged and free and unrestrained.
That is removed more quickly from its position and place which is lighter;
for the heavier bodies are in weight, the more they resist; but the lighter
both moves itself to meet the heavier and is allured by the other.
* * * * *
CHAP. V.
How the Power dwells in the
_Loadstone_.
That a loadstone attracts loadstone, iron and other magnetical bodies, has
been shown above in the previous book, and also with what strength the
magnetick coition is ordered; but now we must inquire how that vigour is
disposed in a magnetick substance. And indeed an analogy must be inferred
from a large loadstone. Any magnetick substance joins itself with a
loadstone strongly, if the loadstone itself is strong; but more weakly,
when it is somewhat imperfect or has been weakened by some flaw. A
loadstone does not draw iron equally well with every part; or a magnetick
substance does not approach every part of a loadstone alike; because a
loadstone has its points, that is its true poles, in which an exceptional
virtue excels. Parts nearer the pole are {72} stronger, those far away more
weak, and yet in all the power is in a certain way equal. The poles of a
terrella are A, B; the æquinoctial is C, D. At A and B the alluring force
seems greatest.
[Illustration]
At C and D there is no force alluring magnetick ends to the body, for the
forces tend toward both poles. But direction is powerful on the æquator. At
C, D, the distances are equal from both poles; therefore iron which is at
C, D, when it is allured in contrary ways, does not adhære with constancy;
but it remains and is joined to the stone, if only it incline to the one or
other side. At E there is a greater power of alluring than at F, because E
is nearer the pole. This is not so because there is really greater virtue
residing at the pole, but since all the parts are united in the whole, they
direct their forces towards the pole. From the forces flowing from the
plane of the æquinoctial towards the pole, the power increases. A fixed
verticity exists at the pole, so long as the loadstone remains whole; if it
is divided or broken, the verticity obtains other * positions in the parts
into which it is divided. For the verticity always changes in consequence
of any change in the mass, and for this cause, if the terrella be divided
from A to B, so that there are two stones, the poles will not be A, B, in
the divided parts, but F, G, and H, I.
[Illustration] {73}
Although these stones now are in agreement with one another, so that F
would not seek H, yet if A was previously the boreal pole[163], F is now
boreal, and H also boreal; for the verticity is not changed (as Baptista
Porta incorrectly affirms in the fourth chapter of his seventh book);
since, though F and H do not agree, so that the one would incline to the
other, yet both turn to the same point of the horizon. If the hemisphere H
I be divided into two quadrants, the one pole takes up its position in H,
the other in I. The whole mass of the stone, as I have said, retains the
site of its vertex constant; and any part of the stone, before it was cut
out from the block[164], might have been the pole or vertex. But concerning
this more under _Direction_. It is important now to comprehend and to keep
firmly in mind that the vertices are strong on account of the force of the
whole, so that (the command being, as it were, divided by the æquinoctial)
all the forces on one side tend towards the north; but those of an opposite
way towards the south, so long as the parts are united, as in the following
demonstration.
[Illustration]
For so, by an infinite number of curves from every point of the equator
dividing the sphere into two equal parts, and from every point of the
surface from the æquator towards the North, and from the æquator towards
the Southern pole, the whole force tends asunder toward the poles. So the
verticity is from the æquinoctial {74} circle towards the pole in each
direction. Such is the power reposed in the undivided stone. From A vigour
is sent to B, from A, B, to C, from A, B, C, to D, and from them likewise
to E. In like manner from G to H, and so forth, as long as the whole is
united. But if a piece A B be cut out (although it is near the æquator),
yet it will be as strong in its magnetical actions as C D or D E, if torn
away from the whole in equal quantity. For no part excels in special worth
in the whole mass except by what is owing to the other adjoining parts by
which an absolute and perfect whole is attained.
_Diagram of Magnetic Vigour
transmitted from the plane of the Æquator
to the peripherery of the terella
or of the earth_
[Illustration]
{75} HEQ is a terrella, E a pole, M the centre, HMQ the æquinoctial plane.
From every point of the æquinoctial plane vigour extends to the periphery,
but by various methods; for from A the formal force is transmitted towards
C, F, N, E, and to every point from C up to E, the pole; but not towards B;
so neither from G towards C. The power of alluring is not strengthened in
the part FHG from that which is in GMFE, but FGH increases the force in the
eminence FE. So no force rises from the internal parts, from the lines
parallel to the Axis above those parallels, but always inwards from the
parallels to the pole. From every point of the plane of the equator force
proceeds to the pole E, but the point F has its powers only from GH, and N
from OH; but the pole E is strengthened from the whole plane HQ. Wherefore
in it the mighty power excels (just as in a palace); but in the
intermediate intervals (as in F) only so much force of alluring is exerted
as the portion HG of the plane can contribute.
* * * * *
CHAP. VI.
How magnetick pieces of Iron and smaller
_loadstones conform themselves to a terrella & to_
the earth itself, and by them are
_disposed_.
Coition of those bodies which are divided, and do not naturally cohære, if
they are free, occurs through another kind of motion. A terrella sends out
in an orbe its powers in proportion to its vigour and quality. But when
iron or any other magnetick of convenient magnitude comes within its orbe
of virtue, it is allured; but the nearer it comes to the body, the more
quickly it runs up to it. They move towards the magnet, not as * to a
centre, nor towards its centre. For they only do this in the case of the
poles themselves, when namely that which is being allured, and the pole of
the loadstone, and its centre, are in the same straight line. But in the
intervening spaces they tend obliquely, just as is evident in the following
figure, in which it is shown how the influence is extended to the adjoining
magneticks within the orbe; in the case of the poles straight out.
{76} [Illustration]
The nearer the parts are to the æquinoctial, the more obliquely are
magneticals allured; but the parts nearer the poles appeal more directly,
at the poles quite straight. The principle of the turning of all
loadstones, of those which are round and those which are long, is the same,
but in the case of the long ones the experiment is easier. For in whatever
form they are the verticity exists, and there are poles; but on account of
bad and unequal form, they are often hindered by certain evils. If the
stone were long, the vertex is at the ends, not on the sides; it allures
more strongly at the vertex. For the parts bring together stronger forces
to the pole in right lines than oblique. So the stone and the earth conform
their magnetick motions by their nature.
* * * * *
CHAP. VII.
On the Potency of the Magnetick Virtue, and on
its nature capable of spreading out into an orbe.
From about a magnetical body the virtue magnetical is poured out on every
side around in an orbe; around a terrella; in the case of other shapes of
stones, more confusedly and unevenly. But yet there exists in nature no
orbe or permanent or essential virtue spread through the air, but a magnet
{77} only excites magneticks at a convenient distance from it. And as light
comes in an instant (as the opticians teach), so much more[165] quickly is
the magnetick vigour present within the limits of its strength; and because
its activity is much more subtile than light, and does not consent with a
non-magnetick substance, it has no intercourse with air, water, or any
non-magnetick; nor does it move a magnetick with any motion by forces
rushing upon it, but being present in an instant, it invites friendly
bodies. And as light strikes an object, so a loadstone strikes a magnetick
body and excites it. And just as light does not remain in the air above
vapours and effluvia, and is not reflected from those spaces, so neither is
the magnetick ray held in air or water. The appearances of things are
apprehended in an instant in mirrors and in the eye by means of light; so
the magnetick virtue seizes upon magneticks. Without the more intangible
and shining bodies, the appearances of things are not seized or reflected;
so without magnetical objects the magnetick power is not perceived, nor are
the forces thus conceived sent back again to the magnetick substance. In
this, however, the magnetick power excels light, in that it is not hindered
by any opaque or solid substance, but proceeds freely, and extends its
forces on every side. In a terrella and globe-shaped loadstone the
magnetick power is extended outside the body in an orbe; in a longer one,
however, not in an orbe, but it is extended in an ambit conformably to the
shape of the stone. As in the somewhat long stone A, the vigour is extended
to the ambient limit F C D, equidistant on every side from the stone A.
[Illustration]
* * * * *
{78} CHAP. VIII.
On the geography of the Earth,
_and of the Terrella_.
Desiring that what follows may be better understood, we must now say
something also about magnetick circles and limits. Astronomers, in order to
understand and observe methodically the motion of the planets and the
revolution of the heavens, and to describe with more accuracy the celestial
attire of the fixed stars, settled upon certain circles and definite limits
in the sky (which geographers also imitate), so that the varied face of the
earth and the beauty of its districts might be delineated. But we, in a way
differing from them, recognize those limits and circles, and have found
very many fixed by nature, not merely conceived by the imagination, both in
the earth and in our terrella. The earth they mark out[166] chiefly by
means of the æquator and the poles; and those limits indeed have been
arranged and marked out by nature. The meridians also indicate straight
paths from pole to pole through distinct points on the æquator; by which
way the magnetick virtue directs its course and moves. But the tropics and
arctic circles, as also the parallels, are not natural limits placed on the
earth; but all parallel circles indicate a certain agreement of the lands
situated in the same latitude, or diametrically opposite. All these the
Mathematicians use for convenience, painting them on globes and maps. In
like manner also in a terrella all these are required; not, however, in
order that its exterior appearance may be geographically delineated, since
the loadstone may be perfect, even, and uniform on all sides. And there are
no upper and lower parts in the earth, nor are there in a terrella; unless
perchance some one considers those parts superior which are in the
periphery, and those inferior which are situated more towards the centre.
* * * * *
{79} CHAP. IX.
On the Æquinoctial Circle of the Earth
_and of a Terrella_.
As conceived by astronomers the æquinoctial circle is equidistant from both
poles, cutting the world in the middle, measures the motions of their
_primum mobile_ or tenth sphere, and is named the zone of the _primum
mobile_. It is called æquinoctial, because when the sun stands in it (which
must happen twice in the year) the days are equal to the nights. That
circle is also spoken of as _æquidialis_, wherefore it is called by the
Greeks [Greek: isêmerinos]. In like manner it is also properly called
Æquator, because it divides the whole frame of the earth between the poles
into equal parts. So also an æquator may be rightly assigned to a terrella,
by which its power is naturally divided, and by the plane of which
permeating through its centre, the whole globe is divided into equal parts
both in quantity and strength (as if by a transverse septum) between
verticities on both sides imbued with equal vigour.
* * * * *
CHAP. X.
Magnetick Meridians of the Earth.
Meridians have been thought out by the geographer, by means of which he
might both distinguish the longitude and measure the latitude of each
region. But the magnetick meridians are infinite, running in the same
direction also, through fixed and opposite limits on the æquator, and
through the poles themselves. On them also the magnetick latitude is
measured, and declinations are reckoned from them; and the fixed direction
in them tends to the poles, unless it varies from some defect and the
magnetick is disturbed from the right way. What is commonly called a
magnetick meridian is not really magnetick, nor is it really a meridian,
but it is understood to pass through the termini of the variation on the
horizon. The variation is a depraved deviation from a meridian, nor is it
fixed and constant in various places on any meridian.
* * * * *
{80} CHAP. XI.
Parallels.
In parallel circles the same strength and equal power are perceived
everywhere, when various magneticks are placed on one and the same parallel
either on the earth or on a terrella. For they are distant from the poles
by equal intervals and have equal tendencies of declination, and they are
attracted and held, and they come together with like forces; just as those
regions which are situated under the same parallel, even if they differ in
longitude, yet we say possess the same quantity of daylight and a climate
equally tempered.
* * * * *
CHAP. XII.
The Magnetick Horizon.
Horizon is the name given to the great circle, separating the things which
are seen from those which are not seen; so that a half part of the heaven
always is open and easily seen by us, half is always hidden. This seems so
to us on account of the great distance of the star-bearing orbe: yet the
difference is as great as may arise from the ratio of the semi-diameter of
the earth compared with the semi-diameter of the starry heaven, which
difference is in fact not perceived by our senses. We maintain, however,
that the magnetick horizon is a plane level throughout touching the earth
or a terrella in the place of some one region, with which plane the
semi-diameter, whether of the earth or of the terrella, produced to the
place of the region, makes right angles on every side. Such a plane is to
be considered in the earth itself and also in the terrella, for magnetick
proofs and demonstrations. For we consider the bodies themselves only, not
the general appearances of the world. Therefore not with the idea of
outlook (which varies with the elevations of the lands), but taking it as a
plane which makes equal angles with the perpendicular, we accept in
magnetick demonstrations a sensible horizon or boundary, not that which is
called by Astronomers the rational horizon.
* * * * *
{81} CHAP. XIII.
On the Axis and Magnetick Poles.
Let the line be called the axis which is drawn in the earth (as in a
terrella) through the centre to the poles. They are called [Greek: poloi]
by the Greeks from [Greek: polein], to turn, and by the Latins they are
also called _Cardines_ or _Vertices_; because the world rotates and is
perpetually carried around them. We are about to show, indeed, that the
earth and a terrella are turned about them by a magnetick influence. One of
them in the earth, which looks towards the Cynosure, is called Boreal and
Arctic; the other one, opposite to this, is called Austral and Antarctic.
Nor do these also exist on the earth or on a terrella for the sake of the
turning merely; but they are also limits of direction and position, both as
respects destined districts of the world, and also for correct turnings
among themselves.
* * * * *
CHAP. XIIII.
Why at the Pole itself the Coition is stronger than in
_the other parts intermediate between the æquator and the pole;_
and on the proportion of forces of the coition in
_various parts of the earth and of the terrella_.
Observation has already been made that the highest power of alluring exists
in the pole, and that it is weaker and more languid in the parts adjacent
to the æquator. And as this is apparent in the declination, because that
disponent and rotational virtue has an augmentation as one proceeds from
the Æquator towards the poles: so also the coition of magneticks grows
increasingly fresh by the same steps, and in the same proportion. For in
the parts more remote from the poles the loadstone does not draw magneticks
straight down towards its own viscera; but they tend obliquely and they
allure obliquely. For as the smallest chords in a circle differ from the
diameter, so much do the forces of attracting differ between themselves in
different parts of the terrella. {82} For since attraction is coition
towards a body, but magneticks run together by their versatory tendency, it
comes about that in the diameter drawn from pole to pole the body appeals
directly, but in other places less directly. So the less the magnetick is
turned toward the body, the less, and the more feebly, does it approach and
adhære. [Illustration] Just as if A B were the poles and a bar of iron or a
magnetick fragment C is allured at the part E; yet the end laid hold of
does not tend towards the centre of the loadstone, but verges obliquely
towards the pole; and a chord drawn from that end obliquely as the
attracted body tends is short; therefore it has less vigour and likewise
less inclination. But as a greater chord proceeds from a body at F, so its
action is stronger; at G still longer; longest at A, the pole (for the
diameter is the longest way) to which all the parts from all sides bring
assistance, in which is constituted, as it were, the citadel and tribunal
of the whole province, not from any worth of its own, but because a force
resides in it contributed from all the other parts, just as all the
soldiers bring help to their own commander. Wherefore also a slightly
longer stone attracts more than a spherical one, since the length from pole
to pole is extended, even if the stones are both from the same mine and of
the same weight and size. The way from pole to pole is longer in a longer
stone, and the forces brought together from other parts are not so
scattered as in a round magnet and terrella, and in a narrow one they agree
more and are better united, and a united stronger force excels and is
preeminent. A much weaker office, however, does a plane or oblong stone
perform, when the length is extended according to the leading of the
parallels, and the pole stops neither on the apex nor in the circle and
orbe, but is spread over the flat. Wherefore also it invites a friend
wretchedly, and feebly retains him, so that it is esteemed as one of an
abject and contemptible class, according to its less apt and less suitable
figure.
* * * * *
{83} CHAP. XV.
*
The Magnetick Virtue which is conceived in Iron is
more apparent in an iron rod than in a piece of iron that
_is round, square, or of other figure_.
Duly was it said before that the longer magnet attracts the greater weight
of iron[167]; so also in a longish piece of iron which has been touched the
magnetick force conceived is stronger when the poles exist at the ends. For
the magnetick forces which are driven from the whole in every part into the
poles are not scattered but united in the narrow ends. In square and other
angular figures the influence is dissipated, and does not proceed in
straight lines or in convenient arcs. Suppose also an iron globe have the
shape of the earth, yet for the same reasons it drags magnetick substances
less; wherefore a small iron sphere, when excited, draws another piece of
iron more sluggishly than an excited rod of equal weight.
* * * * *
CHAP. XVI.
Showing that Movements take place by the Magnetical
Vigour though solid bodies lie between; and on
_the interposition of iron plates_.
Float a piece of iron wire on the surface of water by transfixing it
through a suitable cork; or set a versatory piece of iron on a pin or in a
seaman's compass (a magnet being brought near or moved about underneath),
it is put into a state of motion; neither the water, nor the vessel, nor
the compass-box offering resistance in any way. Thick boards do not
obstruct[168], nor earthen vessels nor marble vases, nor the metals
themselves; nothing is so solid as to carry away or impede the forces
excepting an iron plate. Everything which is interposed (even though it is
very dense) does not carry away its influence or obstruct its path, or
indeed in any way hinder, diminish, or retard it. But all the force is not
suppressed by an iron plate, but it is in some measure diverted aside. For
when the vigour passes into the middle of an iron plate within the orbe of
the magnetick virtue or placed just {84} opposite the pole of the stone,
that virtue is scattered in very large measure towards its extremities; so
that the edges of a small round * plate of suitable size allure iron wires
on every side. This is also apparent in the case of a long iron wand,
which, when it has been touched by a magnet in the middle, has a like
verticity at either end. *
[Illustration]
B is a loadstone, C D a long rod magnetized in the middle A; E being the
Boreal pole; C is an Austral end or pole; in like manner also the end D is
another Austral pole. But observe here the exactness with which a versorium
touched by a pole, when a round plate is interposed, turns towards the same
pole in the same * way as before the interposition, only weaker; the plate
not standing in the way, because the vigour is diverted through the edges
of the small plate, and passes out of its straight course, but yet the
plate retains in the middle the same verticity, when it is in the
neighbourhood of that pole, and close to it; wherefore the versorium tends
towards the plate, having been touched by the same pole. If a loadstone is
rather weak, a versorium hardly turns when a plate is put in between; for
the vigour of the rather weak loadstone, being diffused through the
extremities, passes less through the * middle. But if the plate has been
touched in this way by a pole in the middle and has been removed from the
stone outside its orbe of virtue, then you will see the point of the same
versorium tend in the contrary direction and desert the centre of the small
plate, which formerly it desired; for outside the orbe of virtue it has an
opposite verticity, in the vicinity the same; for in the vicinity it is, as
it were, a part of the loadstone, and has the same pole.
[Illustration]
A is an iron plate near the pole, B a versorium which tends with its point
towards the centre of the small plate, which has been touched by the pole
of the loadstone C. But if the same small plate be {85} placed outside the
orbe of magnetick virtue, the point will not turn towards its centre, but
the cross E of the same versorium does. But an iron globe interposed (if it
is not too large) attracts the * point of the iron on the other side of the
stone. For the verticity of that side is the same as that of the adjoining
pole of the stone. And this turning of the cusp (that is, of the end
touched by that pole) as well as of the cross-end, at a greater distance,
takes place with an iron globe interposed, which would not happen at all if
* the space were empty, because the magnetick virtue is passed on and
continued through magnetick bodies.
[Illustration]
A is a terrella, B an iron globe; between the two bodies is F, a versorium
whose point has been excited by the pole C. In the other figure A is a
terrella, C its pole, B an iron globe; where the versorium tends towards C,
the pole of the terrella, through the iron globe. So a versorium placed
between a terrella and an iron globe vibrates more forcibly towards the
pole of the terrella; because the loadstone sends an instantaneous
verticity into the opposite globe. There is the same efficiency in the
earth, produced from the same cause. For if a revolvable needle is shut up
in a rather thick gold box (this metal indeed excels all others in density)
or a glass or stone box, nevertheless that magnetick needle has its forces
connected and united with the influences of the earth, and the iron will
turn freely and readily (unhindered by its prison) to its desired points,
North and South. * It even does this when shut up in iron caverns, if they
are sufficiently spacious. Whatever bodies are produced among us, or are
artificially forged from things which are produced, consist of matter of
the terrestrial globe; nor do those bodies hinder the prime forces of
nature which are derived from their primary form, nor can they resist them
except by contrary forms. But no forms of mixed bodies are inimical to the
primary implanted earth-nature, although some often do not agree[169] with
one another. But in the case of all those substances which have a material
cause for their inclining (as amber, {86} jet, sulphur), their action is
impeded by the interposition of a body (as paper, leaves, glass, or the
like) when that way is impeded and obstructed, so that that which
exhales[170] cannot reach the corpuscle to be allured. Terrestrial and
magnetick coition and motion, when corporeal impediments are interposed, is
demonstrated also by the efficiencies of other chief bodies due to their
primary form. The moon (more than all the stars) agrees with internal parts
of the earth on account of its nearness and similarity in form. The moon
produces the movements of the waters and the tides of the sea; twice it
fills up the shores and empties them whilst it moves from a certain
definite point in the sky back to the same point in a daily revolution.
This motion of the waters is incited and the seas rise and fall no less
when the moon is below the horizon and in the lowest part of the heavens,
than if it had been raised at a height above the horizon. So the whole mass
of the earth interposed[171] does not resist the action of the moon, when
it is below the earth; but the seas bordering on our shores, in certain
positions of the sky when it is below the horizon, are kept in motion, and
likewise stirred by its power (though they are not struck by its rays nor
illuminated by its light), rise, come up with great force, and recede. But
about the reason of the tides anon[172]; here let it suffice to have merely
touched the threshold of the question. In like manner nothing on the earth
can be hidden from the magnetick disposition of the earth or of the stone,
and all magnetical bodies are reduced to order by the dominant form of the
earth, and loadstone and iron show sympathy with a loadstone though solid
bodies be interposed.
* * * * *
CHAP. XVII.
On the Iron Cap of a Loadstone, with which
it is armed at the pole (for the sake of the
_virtue) and on the efficacy of the same._
Conceive a small round plate, concave in shape, of the breadth of a digit
to be applied to the convex polar surface of a loadstone and skilfully
attached; or a piece of iron shaped like an acorn, rising from the base
into an obtuse cone, hollowed out a little and fitted to the surface of the
stone, to be tied to the loadstone. Let the iron be the best steel,
smoothed, shining, and even. A loadstone with such an appliance, which
before only bore four ounces of iron, will now raise twelve. But the
greatest force of a combining or rather united nature is seen {87} when two
loadstones, armed with iron caps, are so joined by their concurrent
(commonly called contrary) ends, that they mutually * attract and raise one
another. In this way a weight of twenty ounces is raised, when either stone
unarmed would only allure four ounces of iron. Iron unites to an armed
loadstone more firmly than to a loadstone; and on that account raises
greater weights, because the pieces of iron stick more pertinaciously to
one that is armed. For by the near presence of the magnet they are cemented
together, and since the armature[173] conceives a magnetick vigour from its
presence and the other conjoined piece of iron is at the same time endued
with vigour from the presence of the loadstone, they are firmly bound
together. Therefore by the mutual contact of strong pieces of iron, the
cohesion is strong. Which thing is also made clear and is exhibited by
means of rods sticking together, Bk. 3, chap 4[174]; and also when the
question of the concretion of iron dust into a united body was discussed.
For this reason a piece of iron set near a loadstone draws away any
suitable piece of iron from the loadstone, if only it touch the iron;
otherwise it does not snatch it away, though in closest proximity. For
magnetick pieces of iron within the orbe of virtue, or near a loadstone, do
not rush together with a greater endeavour[175] than the iron and the
magnet; but joined they are united more strongly and, as it were, cemented
together, though the substance remain the same with the same forces acting.
* * * * *
CHAP. XVIII.
An armed Loadstone does not endow an
excited piece of Iron with greater vigour
_than an unarmed_.
Suppose there are two pieces of iron, one of * which has been excited by an
armed loadstone, the other by one unarmed; and let there be applied to one
of them another piece of iron of a weight just proportional to its
strength, it is manifest that the remaining one in like manner raises the
same and no more. Magnetick versoria also touched by an armed loadstone
turn with the same velocity and constancy towards the poles of the earth as
those magnetized by the same loadstone unarmed.
* * * * *
{88} CHAP. XIX.
Union with an armed Loadstone is stronger;
_hence greater weights are raised; but the_
coition is not stronger[176], but
_generally weaker_.
An armed magnet raises a greater weight, as is manifest to all; but a piece
of iron moves towards a stone at an equal, or rather greater, distance when
it * is bare, without an iron cap. This must be tried with two pieces of
iron of the same weight and figure at an equal distance, or with one and
the same versorium, the test being made first with an armed, then with an
unarmed loadstone, at equal distances.
* * * * *
[Illustration]
CHAP. XX.
*
An armed Loadstone raises an armed Loadstone,
_which also attracts a third; which likewise_
happens, though the virtue in the first
_be somewhat small_.
Magnets armed cohære firmly when duly joined, and accord into one; and
though the first be rather weak, yet the second one adhæres to it not only
by the strength of the first, but of the second, which mutually give
helping hands; also to the second a third often adheres and in the case of
robust stones, a fourth to the third.
* * * * *
{89}
CHAP. XXI.
*
If Paper or any other Medium be interposed,
an armed loadstone raises no more than an
_unarmed one_.
Observation has shown above that an armed loadstone does not attract at a
greater distance than an unarmed one; yet raises iron in greater quantity,
if it is joined to and made continuous with the iron. But if Paper be
placed between, that intimate cohæsion of the metal is hindered, nor are
the metals cemented together at the same time by the operation of the
magnet.
* * * * *
[Illustration]
CHAP. XXII.
*
That an armed Loadstone draws Iron no more than an
_unarmed one: And that an armed one is more strongly united_
to iron is shown by means of an armed loadstone
_and a polished cylinder of iron_.
If a cylinder be lying on a level surface, of too great a weight for an
unarmed loadstone to lift, and (a piece of paper being interposed) if the
pole of an armed loadstone be joined to the middle of it; if the cylinder
were drawn from there by the loadstone, it would follow rolling; but if no
medium were interposed, the cylinder would be drawn along firmly united
with the armed loadstone, and in no wise rolling. But if the same loadstone
be unarmed, it will draw the cylinder rolling with the same speed as the
armed loadstone with the paper between or when it was wrapped in paper.
Armed loadstones of diverse weights, of the same ore vigour * and form,
cling and hang to pieces of iron of a convenient size and proportionate
figure with an equal proportion of strength. The same is apparent in the
case of unarmed stones. A suitable piece * of iron being applied to the
lower part of a loadstone, which is * hanging from a magnetick body,
excites its vigour, so that the loadstone hangs on more firmly. For a
pendent loadstone clings {90} more firmly to a magnetick body joined to it
above with a hanging piece of iron added to it, than when lead or any other
non-magnetick body is hung on.
A loadstone, whether armed or unarmed, * joined by its proper pole to the
pole of another loadstone, armed or unarmed, makes the loadstone raise a
greater weight by the opposite end[177]. A piece of iron also applied to
the pole of a magnet produces the same result, namely, that the other pole
will carry a greater weight of iron; just as a loadstone with a piece of
iron superposed on it (as in this figure) holds up a piece of iron below,
which it cannot hold, if the upper one be removed. * Magneticks in
conjunction make one magnetick. Wherefore as the mass increases, the
magnetick vigour is also augmented.
An armed loadstone, as well as an unarmed * one, runs more readily to a
larger piece of iron and combines more firmly with a larger piece than with
a lesser one.
* * * * *
CHAP. XXIII.
Magnetick Force causes motion towards unity,
_and binds firmly together bodies which are united_.
Magnetick fragments cohære within their strength well and harmoniously
together. Pieces of iron in the presence of a loadstone (even if they are
not * touching the loadstone) run together, seek one another anxiously and
embrace one another, and when joined are as if they were cemented. Iron *
filings or the same reduced to powder inserted in paper tubes, placed upon
a stone meridionally or merely brought rather close to it, coalesce into
one body, and so many parts suddenly are concreted * and combine; and the
whole company of corpuscles thus conspiring together affects another piece
of iron and attracts it, as if it constituted one integral rod of iron; and
above the stone it is directed toward the North and South. But when they
are removed a long * {91} way from the stone, the particles (as if loosed
again) are separated and move apart singly. In this way also the
foundations of the world are connected and joined and cemented together
magnetically. So let Ptolemy of Alexandria, and his followers, and those
philosophers of ours, be the less terrified if the earth do move round in a
circle, nor threaten its dissolution.
Iron filings, after being heated for a long time, are attracted by a
loadstone, yet not so strongly or from so great a distance as when not
heated. A loadstone loses some of its virtue by too great a heat; for its
humour is set free, whence its peculiar nature is marred. Likewise also, if
iron filings are well burnt in a reverberatory furnace and converted into
saffron of Mars, they are not attracted by a loadstone; but if they are
heated, but not thoroughly burnt, they do stick to a magnet, but less
strongly than the filings themselves not acted upon by fire. For the
saffron has become totally deformate, but the heated metal acquires a
defect from the fire, and the forces in the enfeebled body are less excited
by a loadstone; and, the nature of the iron being now ruined, it is not
attracted by a loadstone.
* * * * *
CHAP. XXIIII.
A piece of Iron placed within the Orbe of a
Loadstone hangs suspended in the air, if on account
_of some impediment it cannot approach it_.
Within the magnetick orbe a piece of iron moves towards the more powerful
points of the stone, if it be not hindered by force or by the material of a
body placed between them; either it falls down from above, or tends
sideways or obliquely, or flies up above. But if the iron cannot reach the
stone on account of some obstacle, it cleaves to it and remains there, but
with a less firm and constant connection, since at greater intervals or
distances the alliance is less amicable. Fracastorio, in the eighth chapter
of his _De Sympathia_, says that a piece of iron is suspended in the air,
so that it can be moved neither up nor down, if a loadstone be placed above
which is able to draw the iron up just as much as the iron itself inclines
downwards with equal force; for thus the iron would be supported in the
air: which thing is absurd; because the force of a magnet is {92} always
the stronger the nearer it is. So that when a piece of iron is raised a
very little from the earth by the force of the magnet, it needs must be
drawn steadily on towards the magnet (if nothing else come in the way) and
cleave to it. Baptista Porta suspends a piece of iron in the air[178] (a
magnet being fixed above), and, by no very subtile process, the iron is
detained by a slender thread from its lower part, so that it cannot rise up
to the stone. The iron is raised upright by the magnet, although the magnet
does not * touch the iron, but because it is in its vicinity; but when the
whole iron on account of its greater nearness is moved by that which
erected it, immediately it hurries with a swift motion to the magnet and
cleaves to it. For by approaching the iron is more and more excited, and
the coition grows stronger.
* * * * *
CHAP. XXV.
Exaltation of the power of the Magnet.
One loadstone far surpasses another in power, since one draws iron of
almost its own weight, another can hardly stir some shreds. Whatever
things, whether animals or plants, are endowed with life need some sort of
nourishment, by which their strength not only persists but grows firmer and
more vigorous. But iron is not, as it seemed to Cardan and to Alexander
Aphrodiseus, attracted by the loadstone in order that it may feed on shreds
of it, nor does the loadstone take up vigour from iron filings as if by a
repast on victuals. Since Porta had doubts on this and resolved to test it,
he took a loadstone of ascertained weight, and buried it in iron filings of
not unknown weight; and when he had left it there for many months, he found
the stone of greater weight, the filings of less. But the difference was so
slender that he was even then doubtful as to the truth. What was done by
him does not convict the stone of voracity, nor does it show any nutrition;
for minute portions of the filings are easily scattered in handling. So
also a very fine dust is insensibly born on a loadstone in some very slight
quantity, by which something might have been added to the weight of the
loadstone but which is only a surface accretion and might even be wiped off
with no great difficulty. Some think that a weak and sluggish stone can
bring itself back into better condition, and that a very powerful one also
might present it with the highest powers. Do they acquire strength like
animals when {93} they eat and are sated? Is the medicine prepared by
addition or subtraction? Is there anything which can re-create this primary
form or bestow it anew? And, certes, nothing can do this which is not
magnetical. Magneticks can restore a certain soundness to magneticks (when
not incurable); some can even exalt them beyond their proper strength; but
when a body is at the height of perfection in its own nature, it is not
capable of being strengthened further. So that that imposture of
Paracelsus, who affirms that the force and virtue can be increased and
transmuted tenfold, turns out to be the more infamous. The method of
effecting this is as follows, viz., you make it semi-incandescent in a fire
of charcoal (that is, you heat it very hot), so that it does not become
red-hot, however, and immediately slake it, as much indeed as it can
imbibe, in oil of saffron of Mars, made from the best Carynthian steel. "In
this way you will be able so to strengthen a loadstone that it can draw a
nail out of a wall and accomplish many other like wonderful things, which
are not possible for a common loadstone." But a loadstone thus slaked in
oil not only does not gain power, but suffers also a certain loss of its
inborn strength. A loadstone is improved if polished and rubbed with steel.
Buried in filings of the best iron or of pure steel, not rusty, it
preserves its strength. Sometimes also a somewhat good and strong one gains
[Illustration] some strength when it is rubbed on the pole of another, on
the opposite part, and receives virtue. In all these experiments it is an
advantage to observe the pole of the earth, and to adjust according to
magnetick laws the stone which we wish to strengthen; which we shall set
forth below. A somewhat powerful and fairly large loadstone increases the
strength of a loadstone as it does of iron. A loadstone being placed over
the boreal pole of a loadstone, * {94} the boreal pole becomes stronger,
and an iron rod (like an arrow) sticks to the boreal pole A, but not at all
to the pole B. The pole A also, when it is at the top in a right line with
the axis of both loadstones joined in accordance with magnetick laws,
raises the rod to the perpendicular, which it cannot do if the large
loadstone be removed, on account of its own weaker strength. But as a small
iron globe, when placed above the pole of a terrella, raises the rod to the
* perpendicular, so, when placed at the side, the rod is not directed
towards the centre of the globe, but is raised obliquely and cleaves
anywhere, because the pole in a round piece of iron is always the point
which is joined most closely to the pole of the terrella and is not
constant as in a smaller terrella. The parts of the earth, as of all
magneticks, are in agreement and take delight in their mutual proximity; if
placed in the highest power, they do not harm their inferiors, nor slight
them; there is a mutual love among them all, a perennial good feeling. The
weaker loadstones are re-created by the more powerful, and the less
powerful cause no harm to the stronger. But a powerful one attracts and
turns a somewhat strong one more than it does an impotent one. Because a
strenuous one confers a stronger activity, and itself hastens, flies up to
the other, and solicits it more keenly; therefore there is a more certain
and a stronger co-action and cohærency.
* * * * *
CHAP. XXVI.
Why there should appear to be a greater love between
_iron and loadstone, than between loadstone and loadstone, or_
between iron and iron, when close to the loadstone,
_within its orbe of virtue._
Magnet attracts magnet, not in every part and on every side with equal
conditions, as iron, but at one and a fixed point; therefore the poles of
both must be exactly disposed, otherwise they do not cleave together duly
and strongly. But this disposition is not easy and expeditious; wherefore a
loadstone seems not to conform to a loadstone, when nevertheless they agree
very well together. A piece of iron by the sudden impression of a loadstone
is not only allured by the stone, but is renewed, its forces being drawn
forth; by which it follows and solicits the loadstone with no less impulse,
and even leads another piece of iron captive. Let there be a small iron
spike above a loadstone clinging firmly to it; if you apply an unmagnetized
rod of iron to the spike, not, however, {95} so that it touches the stone,
you will see the spike when it has touched the iron, leaving the loadstone,
follow the rod, try to grasp it by leaning toward it, and (if it should
touch it) cleave firmly to it: for a piece of iron, when united and joined
to another piece of iron placed within the orbe of virtue of the loadstone,
draws it more strongly than does the loadstone itself. The natural
magnetick virtue, confused and dormant in the iron, is aroused by the
loadstone, is linked to the loadstone, and rejoices with it in its primary
form; then smelted iron becomes a perfect magnetick, as robust as the
loadstone itself. For as the one imparts and stirs, so the other conceives,
and being stirred remains in virtue, and pours back the forces also by its
own activity. But since iron is more like iron than loadstone, and the
virtue in both pieces of iron is exalted by the proximity of the loadstone,
so in the loadstone itself, in case of equal strength, likeness of
substance prevails, and iron gives itself up rather to iron, and they are
united by their very similar homogenic powers. Which thing happens not so
much from a coition, as from a firmer unition; and a knob or snout of
steel, fixed skilfully on the pole of the stone, raises greater weights of
iron than the stone of itself could. When steel or iron is smelted from
loadstone or iron ore, the slag and corrupt substances are separated from
the better by the fusion of the material; whence (in very large measure)
that iron contains the nature of the earth, purified from alien flaw and
blemish, and more homogenic and perfect, though deformed by the fusion. And
when that material indeed is provoked by a loadstone, it conceives the
magnetick virtues, and within their orbe is raised in strength more than
the weaker loadstone, which with us is often not free from some admixture
of impurities.
* * * * *
CHAP. XXVII.
*
The Centre of the Magnetick Virtues in the earth
is the centre of the earth; and in a terrella
_is the centre of the stone_.
Rays of magnetick virtue spread out in every direction in an orbe; the
centre of this orbe is not at the pole (as Baptista Porta reckons, Chap.
22), but in the centre of the stone and of the terrella. So also the centre
of the earth is the centre of the magnetick motions of the earth; though
magneticks are not borne directly toward the centre by magnetical motion,
except when they are attracted by the true pole. For since the formal {96}
power of the stone and of the earth does not promote anything but the unity
and conformity of disjoined bodies, it comes about that everywhere at an
equal distance from the centre or from the circumference, just as it seems
to attract perpendicularly at one place, so at another it is able even to
dispose and to turn, provided the stone is not uneven in virtue. For if at
the distance C from the pole D the stone is able to allure a versorium, *
at an equally long interval above the æquator at A that stone can also
direct and turn the versorium. So the very centre and middle of the
terrella is the centre of its virtue, and from this to the circumference of
the orbe (at equal intervals on every side) its magnetick virtues are
emitted.
[Illustration]
* * * * *
CHAP. XXVIII.
A Loadstone attracts magneticks not only to a
fixed point or pole, but to every part of a
_terrella save the æquinoctial zone_.
Coitions are always more powerful when poles are near poles, since in them
by the concordancy of the whole there exists a stronger force; wherefore
the one embraces the other more strongly. Places declining from the poles
have attractive forces, but a little weaker and languid in the ratio of
their distance; so that at length on the æquinoctial circle they are
utterly enervated and evanescent. Neither do even the poles attract as
mathematical points; nor do magneticks come into conjunction by their own
poles, only on the poles of a loadstone. But coition {97} is made on every
part of the periphery, both Northern and Southern, by virtue emanating from
the whole body; magneticks nevertheless incline languidly towards
magneticks in the parts bordering on the æquator, but quickly in places
nearer the pole. Wherefore not the poles, not the parts alone nearest to
the pole allure and invite magneticks, but magneticks are disposed and
turned round and combine with magneticks in proportion as the parts facing
and adjoined unite their forces together, which are always of the same
potency in the same parallel, unless they are distributed otherwise from
causes of variation.
* * * * *
CHAP. XXIX.
On Variety of Strength due to Quantity
_or Mass_.
Quite similar in potency are those stones which are of the same mine, and
not corrupted by adjacent ores or veins. Nevertheless that which excels in
size shows greater powers, since it seizes greater weights and has a wider
orbe of virtue. For a loadstone weighing one ounce does not lift a large
nail as does one weighing a pound, nor does it rule so widely, nor extend
its forces; and if from a loadstone of a pound weight a portion is taken
away, something of its power will be seen to go also; for when a portion is
abstracted the virtue is lessened. But if that part is properly applied and
united to it, though it is not fastened * to nor grown into it, yet by the
application it obtains its pristine power and its vigour returns.
Sometimes, however, when a part is taken away, the virtue turns out to be
stronger on account of the * bad shape of the stone, namely, when the
vigour is scattered through inconvenient angles. In various species the
ratio is various, for one stone of a drachm weight draws more than another
of twenty pounds. Since in very many the influence is so effete that it can
hardly be perceived, those weak stones are surpassed by prepared pieces of
clay. But, it may be asked[179], if a stone of the same species and
goodness weighing a drachm would seize upon a drachm of iron, would a stone
of an ounce weight seize on an ounce, a pound on a pound, and so on? And
this is indeed true; for it both strains and remits its strength
proportionately, so that if a loadstone, one drachm of which would attract
one drachm of iron, were in equal proportion applied either to a suitably
large obelisk or to an immense pyramid of iron, it would lift it directly
in such {98} proportion and would draw it towards itself with no greater
effort of its nature or trouble than a loadstone of a drachm weight
embraces a drachm. But in all such experiments as this let the vigour of
the magnets be equal; let there be also a just proportion in all of the
shapes of the stones, and let the shape of the iron to be attracted be the
same, and the goodness of the metal, and let the position of the poles of
the loadstones be most exact. This is also no less true in the case of an
armed loadstone than of an unarmed one. For the sake of experiment, let
there be given a loadstone of eight ounces weight, which when armed lifts
twelve ounces of iron; if you cut off from that loadstone a certain
portion, which when it has been * reduced to the shape of the former whole
one is then only of two ounces, such a loadstone armed lifts a piece of
iron applied to it of three ounces, in proportion to the mass. In this
experiment also the piece of iron of three ounces ought to have the same
shape as the former one of twelve ounces; if that rose up into a cone, it
is necessary that this also in the ratio of its mass should be given a
pyramidal shape proportioned to the former.
* * * * *
CHAP. XXX.
The Shape and Mass of the Iron are of most
_importance in coition_.
Observation has shown above that the shape and mass of the loadstone have
great influence in magnetick coitions; likewise also the shape and mass of
the iron bodies give back more powerful and steady forces. Oblong iron rods
are both drawn more quickly to a loadstone and cleave to it with greater
obstinacy than round or square pieces, for the same reasons which we have
proven in the case of the loadstone. But, moreover, this is also worthy of
observation, that a smaller piece of iron, to which is hung a weight of
another material, so that it is altogether in weight equal to another large
whole piece of iron of a right weight * (as regards the strength of the
loadstone), is not lifted by the loadstone as the larger piece of iron
would be. For a smaller piece of iron does not join with a loadstone so
firmly, because it sends back less strength, and only that which is
magnetick conceives strength; the foreign material hung on cannot acquire
magnetick forces.
* * * * *
{99} CHAP. XXXI.
On Long and Round Stones.
Pieces of iron join more firmly with a long stone than with a round one,
provided that the pole of the stone is at the extremity and end of its
length; because, forsooth, in the case of a long stone, a magnetick is
directed at the end straight towards the body in which the virtue proceeds
in straighter lines and through the longer diameter. But a somewhat long
stone has but little power on the side, much less indeed than a round one.
It is demonstrable[180], indeed, that at A and B the coition is * stronger
in a round stone than at C and D, at like distances from the pole.
[Illustration]
* * * * *
CHAP. XXXII.
Certain Problems and Magnetick Experiments about
the Coition, and Separation, and regular Motion
_of bodies magnetical_.
Equal loadstones come together with equal incitation. *
Also magnetick bodies of iron, if alike in all respects, * come together
when excited with similar incitation.
Furthermore, bodies of iron not excited by a * loadstone, if they are alike
and not weighed down by their bulk, move towards one another with equal
motion.
Two loadstones, disposed on the surface of some water in {100} suitable
skiffs, if they are drawn up suitably within their orbes of virtue, incite
one another mutually to an embrace. So a proportionate * piece of iron in
one skiff hurries with the same speed towards the loadstone as the
loadstone itself in its boat strives towards the iron. From their own
positions, indeed, they are so borne together, that they are joined and
come to rest at length in the middle of the space. Two iron wires
magnetically excited, floating in water by means of * suitable pieces of
cork, strive to touch and mutually strike one another with their
corresponding ends, and are conjoined.
Coition is firmer and swifter than repulsion and separation in * equal
magnetick substances. That magnetick substances are more sluggishly
repelled than they are attracted is manifest in all magnetical experiments
in the case of stones floating on water in suitable skiffs; also in the
case of iron wires or rods swimming (transfixed through corks) and well
excited by a loadstone, and in the case of versoria. This comes about
because, though there is one faculty of coition, another of conformation or
disposition, repulsion and aversion is caused merely by something
disposing; on the other hand, the coming together is by a mutual alluring
to contact and a disposing, that is, by a double vigour.
A disponent vigour is often only the precursor of coition, in order that
the bodies may stand conveniently for one another before conjunction;
wherefore also they are turned round to the corresponding ends, if they can
[not][181] reach them through the hindrances.
[Illustration]
If a loadstone be divided through a meridian into two equal parts, the
separate parts mutually repel one another, the poles being * placed
directly opposite one another at a convenient and equal distance. They
repel one another also with a greater velocity than when pole is put
opposite pole incongruously. Just as the part B of the loadstone, placed
almost opposite the part A, repels it floating in its skiff, because D
turns away from F, and E from C; but if B is exactly joined with A again,
they agree and become one body {101} magnetical; but in proximity they
raise enmities. But if one part of the stone is turned round, so that C
faces D and F faces E, then A pursues B within its orbe until they are
united.
The Southern parts of the stone avoid the Southern parts, and the Northern
parts the Northern. Nevertheless, if by force you move up the Southern cusp
of a piece of iron too near the Southern part of the stone, the cusp is
seized and both are linked together in friendly embraces: because it
immediately reverses the implanted verticity of the iron, and it is changed
by the presence of the more powerful stone, which is more constant in its
forces than the iron. For they come together according to their nature, if
by reversal and mutation true conformity is produced, and just coition, as
also regular direction. Loadstones of the same shape, size, and vigour,
attract one another mutually with like efficacy, and in the opposite
position repel one another mutually with a like vigour.
Iron rods not touched, though alike and equal, do yet often act * upon one
another with different forces; because as the reasons of their acquired
verticity, also of their stability and vigour, are different, so the more
strongly they are excited, the more vigorously do they incite.
Pieces of iron excited by one and the same pole mutually repel * one
another by those ends at which they were excited; then also the opposite
ends to those in these iron pieces raise enmities one to another.
In versoria whose cusps have been rubbed, but not their cross-ends, * the
crosses mutually repel one another, but weakly and in proportion to their
length.
In like versoria the cusps, having been touched by the same * pole of the
loadstone, attract the cross-ends with equal strength.
In a somewhat long versorium the cross-end is attracted rather * weakly by
the cusp of a shorter iron versorium; the cross of the shorter more
strongly by the cusp of the longer, because the cross of the longer
versorium has a weak verticity, but the cusp has a stronger.
The cusp of a longer versorium drives away the cusp of a * shorter one more
vehemently than the cusp of the shorter the cusp of the longer, if the one
is free upon a pin, and the other is held in the hand; for though both were
equally excited by the same loadstone, yet the longer one is stronger at
its cusp on account of its greater mass.
The Southern end of an iron rod which is not excited attracts * the
Northern, and the Northern the Southern; moreover, also the Southern parts
repel the Southern, and the Northern the Northern.
If magnetick substances are divided or in any way broken in pieces, each
part has a Northern and a Southern end.
{102} A versorium is moved as far off by a loadstone when an obstacle * is
put in the way, as through air and an open medium.
Rods rubbed upon the pole of a stone strive after the same pole * and
follow it. Therefore Baptista Porta errs when he says, chapter 40[182], "If
you put that part to it from which it received its force, it will not
endure it, but drives it from it, and draws to it the contrary and opposite
part."
The principles of turning round and inclining are the same in the case of
loadstone to loadstone, of loadstone to iron, of iron also to iron.
When magnetick substances which have been separated by force and dissected
into parts flow together into a true union and are suitably connected, the
body becomes one, and one united virtue, nor have they diverse ends.
The separate parts assume two opposite poles, if the division has * not
been made along a parallel: if the division has been made along a parallel,
they are able to retain one pole in the same site as before.
Pieces of iron which have been rubbed and excited by a loadstone are more
surely and swiftly seized by a loadstone at fitting ends than such as have
not been rubbed.
If a spike is set up on the pole of a loadstone, a spike or style * of iron
placed on the upper end is strongly cemented to it, and draws away the
erect spike from the terrella when motion is made.
If to the lower end of the erect spike the end of another spike * is
applied, it does not cohære with it, nor do they unite together.
As a rod of iron draws away a piece of iron from a terrella, so is it also
with a minute loadstone and a lesser terrella, though weaker in strength.
[Illustration]
The piece of iron C comes into conjunction with the terrella A, and the
vigour in it is magnetically exalted and excited, both in the adjoining end
and in the other also which is turned away through {103} its conjunction
with the terrella. The end that is turned away also conceives vigour from
the loadstone B; likewise the pole D of that loadstone is powerful on
account of its suitable aspect and the nearness of the pole E of the
terrella. Several causes therefore concur why the piece of iron C should
cleave to the terrella B, to which it is joined more firmly than to the
terrella A; the vigour excited in the rod, the vigour also excited in the
stone B, and the strength implanted in B concur; therefore D is more firmly
cemented magnetically with C than E with C.
But if you were to turn the vertex F round to the iron C, C would not
adhære to F as formerly to D; for stones so arranged being within the orbe
of virtue are placed contrary to natural order; wherefore F does not
receive power from E.
Two loadstones or excited pieces of iron, duly cohæring, fly * asunder on
the approach of another more powerful loadstone or magnetized piece of
iron. Because the new-comer repels the other with its opposing face, and
dominates it, and ends the relationship of the two which were formerly
joined. So the forces of the other are lessened and succumb; but if it
conveniently could, being diverted of its association with the weaker, and
rolling round, it would turn about to the stronger. Wherefore also
magnetick bodies suspended in the air fall when a loadstone is brought near
them with an opposing face, not (as Baptista Porta teaches) because the
faculty of both those which were joined before grows faint and torpid, for
no face can be hostile to both the ends which cohære, but to one only; and
when the stronger loadstone, coming fresh with opposing face, impels this
further from it, it is put to flight by the friendly reception of the
former.
* * * * *
CHAP. XXXIII.
On the Varying Ratio of Strength, and of the Motion
_of coition, within the orbe of virtue_.
Should a very large weight, which at a very small distance is drawn towards
a loadstone, be divided into ever so many equal parts, and should the
radius of the orbe of magnetick attraction be divided into the same number
of parts, the like named parts of the weight will correspond to the
intermediate parts of the radius.
The orbe of virtue extends more widely than the orbe of motion of any
magnetick; for the magnetick is affected at its extremity, even if it is
not moved with local motion, which effect is produced {104} by the
loadstone being brought nearer. A small versorium also is turned when a
good distance off, even if at the same distance it would not flow towards
the loadstone, though free and disengaged from impediment.
The swiftness of the motion of a magnetick body to a loadstone is dependent
on either the power of the loadstone, on its mass, on its shape, on the
medium, or on its distance within the magnetick orbe.
A magnetick moves more quickly towards a more powerful * stone than towards
a sluggish one in proportion to the strength, and [as appears] by a
comparison of the loadstones together. A lesser mass of iron also is
carried more quickly towards a loadstone, just as also one that is a little
longer in shape. The swiftness of magnetick motion towards a loadstone is
changed by reason of the medium; for bodies are moved more quickly in air
than in water, and in clear air than in air that is thick and cloudy.
By reason of the distance, the motion is quicker in the case of bodies near
together than when they are far off. At the limits of the orbe of virtue of
a terrella a magnetick is moved feebly and slowly. At very short distances
close to the terrella the moving impetus is greatest.
A loadstone which in the outmost part of its orbe of virtue * hardly moves
a versorium when one foot removed from it, doth, if a long piece of iron is
joined to it, attract and repel the versorium more strongly with its
opposite poles when even three feet distant. The result is the same whether
the loadstone is armed or unarmed. Let the iron be a suitable piece of the
thickness of the little finger.
For the vigour of the loadstone excites verticity in the iron and proceeds
in the iron and through the iron much further than it extends through the
air.
The vigour proceeds even through several pieces of iron (joined * to one
another end to end), not so regularly, however, as through one continuous
solid.
Dust of steel placed upon paper rises up when a loadstone is moved near
above it in a sort of steely hairiness; but if the loadstone is placed
below, such a hairiness is likewise raised.
Steel dust (when the pole of a loadstone is placed near) is cemented * into
one body; but when it desires coition with the loadstone, the mass is split
and it rises in conglomerated parts.
But if there is a loadstone beneath the paper, the mass is split in the
same way and many portions result, each of which consists of very many
parts, and remains cemented together, as individual bodies. Whilst the
lower parts of these pursue greedily the pole of the loadstone placed
directly beneath, even they also are raised up as magnetick wholes, just as
a small iron wire of the length of a grain or two grains of barley is
raised up, both when the loadstone is moved near both beneath and above.
* * * * *
{105} CHAP. XXXIIII.
Why a Loadstone should be stronger in its poles
in a different ratio; as well in the Northern
_regions as in the Southern_.
The extraordinary magnetick virtue of the earth is * remarkably
demonstrated by the subtility of the following magnetical experiment. Let
there be given a terrella of no contemptible power, or a long loadstone
with equal cones as polar extremities; but in any other shape which is not
exactly round error is easy, and the experiment difficult. In the Northern
regions, raise the true North pole of the terrella above the horizon
straight toward the zenith; it is demonstrable that it raises up a larger
iron spike on its North pole, than the South pole of the same terrella is
able to raise, when turned in the same way toward the highest point of the
sky. The same thing is shown by a small terrella placed in the same way
above a larger.
[Illustration]
Let _a b_ be the earth or a somewhat large terrella, also _a b_ a smaller
terrella. There is set up above the Northern pole of the smaller terrella a
spike larger than the pole _b_ of the smaller terrella can raise, if it is
turned round to the higher parts. And the pole _a_ of the {106} smaller
terrella has its strength from the larger, declining from the Zenith to the
plane of the horizon or to the level. But now, if, * leaving the terrella
disposed in the same way, you bring a piece of iron to the lower and
Southern pole, it will attract and retain a greater weight than the Boreal
pole could, if it were turned round to the lower parts. Which thing is
demonstrated thus: let A be the earth or a terrella; E the Boreal pole or
some place in some great latitude; B a rather large terrella above the
earth or a smaller terrella on the top of a larger; D its Southern pole. It
is manifest that D (the Southern pole) attracts a larger piece of iron, C,
than F (the Boreal pole) will be able to, if it is turned round downward to
the position D, toward the earth or the terrella in the Northern regions.
[Illustration]
Magneticks acquire strength through magneticks, if they are properly placed
according to their nature, in near neighbourhood and within the orbe of
virtue. Wherefore when a terrella is placed on the earth or on a terrella,
so that its Southern pole is turned round toward the Northern pole, its
Northern pole, however, turned away from the Northern pole, the influence
and strength of {107} its poles are increased. And so the Northern pole of
a terrella in such a position lifts up a larger spike than the Southern
pole, if the Southern pole is turned away. Similarly the Southern pole in a
proper and natural arrangement, acquiring strength from the earth or from a
larger terrella, attracts and retains larger rods of iron. In * the other
part of the terrestrial globe toward the South, as also in the Austral
portion of a terrella, the reasoning is converse; for the Southern pole of
the terrella being turned away is more robust, as also the Northern pole
when turned round. The more a region on the earth is distant from the
æquinoctial (as also in a larger terrella), the larger is the accession of
strength perceived; near the æquator, indeed, the difference is small, but
on the æquator itself null; at the poles finally it is greatest.
* * * * *
CHAP. XXXV.
On a Perpetual Motion Machine, mentioned
by authors, by means of the attraction
_of a loadstone_.
Cardan writes[183] that out of iron and the Herculean stone can be made a
perpetual motion machine; not that he himself had ever seen one, but only
conceived the idea from an account by Antonius de Fantis[184], of Treves.
Such a machine he describes, Book 9, _De Rerum Varietate_. But they have
been little practised in magnetick experiments who forge such things as
that. For no magnetick attraction can be greater (by any skill or by any
kind of instrument) than the retention. Things which are joined and those
which are approaching near are retained with a greater force than those
which are enticed and set in motion, and are moved; and that coition is, as
we have shown above, a motion of both, not an attraction of one. Such a
machine Peter Peregrinus feigned many centuries before or else depicted one
which he had received from others, and one which was much better fitted for
the purpose. Johannes Taysnier published it also, spoiled by wretched
figures, and copied out the whole theory of it word for word. O that the
gods would at length bring to a miserable end such fictitious, crazy,
deformed labours, with which the minds of the studious are blinded!
* * * * *
{108} CHAP. XXXVI.
How a more robust Loadstone may be
_recognized_.
Very powerful loadstones sometimes lift into the air a weight of iron equal
to their own; a weak one barely attracts a slender wire. Those therefore
are more robust which appeal to and retain larger bodies, if there is no
defect in their form, or the pole of the stone is not suitably moved up.
Moreover, when placed in a boat a keener influence turns its own poles
round more quickly to the poles of the earth or the limits of variation on
the horizon. One which performs its function more feebly indicates a defect
and an effete nature. There must always be a similar preparation, a similar
figure, and a like size; for in such as are very dissimilar and unlike, the
experiment is doubtful. The method of testing the strength is the same also
with a versorium in a place somewhat remote from a loadstone; for the one
which is able to turn the versorium round at the greater distance, that one
conquers and is held the more potent. Rightly also is the force of a
loadstone weighed in a balance by B. Porta; a piece of loadstone is placed
in one scale-pan, in the other just as much weight of something else, so
that the scale-pans hang level. Soon a piece of iron lying on the table is
adjusted so that it sticks to the loadstone placed in the scale, and they
cling together most perfectly, according to their friendly points; into the
other scale-pan sand is gradually thrown, and that until the scale in which
the loadstone is placed is separated from the iron. Thus by weighing the
weight of sand, the magnetick force becomes known. Similarly also it will
be pleasing to try with another stone, in equilibrium, the weight of the
sand being observed, and to find out the stronger by means of the weights
of sand. Such is the experiment of Cardinal Cusan in his _De
Staticis_[185], from whom it would seem that B. Porta learnt the
experiment. The better loadstones turn themselves round more quickly toward
the poles or points of variation; then they also lead along and turn round
more quickly, according to the greater quantity and mass of wood, a boat
and other stuff. In a declination instrument, the more powerful force of a
loadstone is looked for and required. Those therefore are more lively when
they get through their work readily, and pass through and come back again
with speed, and swiftly at length settle at their own point. Languid and
effete ones move more sluggishly[186], settle more tardily, adhære more
uncertainly, and are easily disturbed from their possession.
* * * * *
{109} CHAP. XXXVII.
Use of a Loadstone as it affects
_iron._
By magnetick coition we test iron ore in a blacksmith's forge. It is burnt,
broken in pieces, washed and dried, in which way it lays down its alien
humours; in the bits collected from the washing is placed a loadstone,
which attracts the iron dust to itself; this, being brushed off with
feathers, is received in a crucible, and the loadstone is again placed in
the bits collected from the washing, and the dust wiped off, as long as any
remains which it will attract to itself. This is then heated in the
crucible along with _sal nitri_[187] until it is liquid, and from this a
small mass of iron is cast. But if the loadstone draws the dust to itself
quickly and readily, we conjecture that the iron ore is rich; if slowly,
poor; if it seems altogether to reject it, there is very little iron in it
or none at all. In like manner iron dust can be separated from another
metal. Many tricks there are also, when iron is secretly applied to lighter
bodies, and, being attracted by the motion of a loadstone which is kept out
of sight, causes movements which are amazing to those who do not know the
cause. Very many such indeed every ingenious mechanician will perform by
sleight of hand, as if by incantations and jugglery[188].
* * * * *
CHAP. XXXVIII.
On Cases of Attraction in other Bodies.
Very often the herd of philosophizers and plagiarists repeat from the
records of others in natural philosophy opinions and errors about the
attractions of various bodies; as that Diamond attracts iron, and snatches
it away from a magnet; that there are various kinds or magnets, some which
attract gold, others silver, brass, lead; even some which attract flesh,
water, fishes. The flame of sulphur is said to seek iron and stones; so
white naphtha is said to attract fire. I have said above that {110}
inanimate natural bodies do not attract, and are not attracted by, others
on the earth, excepting magnetically or electrically. Wherefore it is not
true that there are magnets which attract gold or other metals; because a
magnetick substance draws nothing but magnetick substances. Though
Fracastorio says that he has shown a magnet drawing silver; if this were
true, it must have happened on account of iron skilfully mixed with that
silver or concealed in it, or else because nature (as she does sometimes,
but rarely) had mixed iron with the silver; iron indeed is rarely mixed
with silver by nature; silver with iron very rarely or never. Iron is mixed
with silver by forgers of false coin or from the avarice of princes in the
coining of money, as was the case with the denarius of Antony[189],
provided that Pliny is recording a true incident. So Cardan (perhaps
deceived by others) says that there is a certain kind of loadstone which
draws silver; he adds a most foolish test of this: "If therefore" (he says)
"a slender rod of silver be steeped in that in which a versatory needle has
stood, it will turn toward silver (especially toward a large quantity)
although it be buried; by this means anyone will be able easily to dig up
concealed treasures." He adds that "it should be very good stone, such as
he has not yet seen." Nor indeed will either he or anyone else ever see
such a stone or such an experiment. Cardan brings forward an attraction of
flesh, wrongly so named and very dissimilar from that of the loadstone; for
his _magnes creagus_ or flesh-magnet, from the experiment that it sticks to
the lips, must be hooted out from the assembly of loadstones, or by all
means from the family of things attractive. Lemnian earth, ruddle, and very
many minerals do this, and yet they are fatuously said to attract. He will
have it that there is another loadstone, as it were, a third species, into
which, if a needle is driven and afterwards stuck into the body, it is not
felt. But what has attraction to do with stupefaction, or stupor with a
Philosopher's intellect, when he is discoursing about attraction? There are
many stones, both found in nature and made by art, which have the power of
stupefying. Sulphur flame is said by some to attract, because it consumes
certain metals by its power of penetration. So white naphtha attracts
flame, because it gives off and exhales an inflammable vapour, on which
account it is kindled at some distance, just as the smoke of a recently
extinguished candle takes fire again from another flame; for fire creeps to
fire through an inflammable medium. Why the sucking fish Echineis or the
Remora should stay ships has been variously treated by Philosophers, who
are often accustomed to fit this fable (as many others) to their theories,
before they find out whether the thing is so in nature. Therefore, in order
that they may support and agree with the fatuities of the ancients, they
put forward even the most fatuous ratiocinations and ridiculous problems,
cliffs that attract, where the {111} sucking fish tarry, and the necessity
of some vacuum, I know not what, or how produced. Pliny and Julius Solinus
make mention of a stone Chatochitis[190]. They say that it attracts flesh,
and keeps hold of the hands, just as a loadstone does iron, and amber
chaff. But that happens only from a stickiness and from glue contained in
it, since it sticks more easily to the hands when they are warm. Sagda or
Sagdo[191], of the colour of a sard, is a precious stone mentioned by
Pliny, Solinus, Albertus, and Evax[192]; they describe its nature and
relate, on the authority of others, that it specially attracts wood to
itself. Some even babble that woods cannot be wrenched away except they are
cut off. Some also narrate that a stone is found which grows pertinaciously
into ships, in the same way as certain testacea on long voyages. But a
stone does not draw because it sticks; and if it drew, it would certainly
draw shreds electrically, Encelius saw in the hands of a sailor such a
stone of feeble virtue, which would hardly attract even the smallest twigs;
and in truth, not of the colour of the sard. So Diamond, Carbuncle,
Crystal, and others do attract. I pass over other fabulous stones;
Pantarbe, about which Philostratus writes that it draws other stones to
itself; Amphitane also, which attracts gold. Pliny in his origin of glass
will have it that a loadstone is an attractor of glass, as well as of iron.
For in his method of preparing glass, when he has indicated its nature, he
subjoins this about loadstone. "Soon (such is the astute and resourceful
craft) it was not content to have mixed natron; loadstone also began to be
added, since it was thought to attract to itself the liquor of glass (as it
does iron)." Georgius Agricola writes that to the material of glass (sand
and natron) one part also of loadstone is added. "Because that force is
believed, in our times just as in former times, to attract the liquor of
glass to itself, as it attracts iron to itself, purges it when drawn, and
makes clear glass from green or muddy; but the fire afterwards burns up the
loadstone." It is true indeed that some sort of _magnes_ (as the magnesia
of the glass-makers imbued with no magnetick virtues) is sometimes put in
and mixed with the material of the glass; not, however, because it attracts
glass. But when a loadstone is burnt, it does not lay hold of iron at all,
nor is iron when red-hot allured by any loadstone; and loadstone also is
burnt up by more powerful fires and loses its attractive potency. Nor is
this a function of loadstone alone in the glass furnaces; but also of
certain pyrites and of some easily combustible iron ores, which are the
only ones used by our glass-makers, who make clear, bright glass. They are
mixed with the sand, ashes, and natron (just as they are accustomed to make
additions in the case of metallick ores whilst they are smelted), so that
when the material slows down into glass, the green and muddy colour of the
glass may be purged by the penetrating heat. For no other material becomes
so hot, {112} or bears the fire for such a convenient time, until the
material of the glass is perfectly fluid, and is at the same time burnt up
by that ardent fire. It happens, however, sometimes, that on account of the
magnetick stone, the magnesia, or the ore, or the pyrites, the glass has a
dusky colour, when they resist the fire too much and are not burnt up, or
are put in in too great quantity. Wherefore manufacturers are seeking for a
stone suitable for them, and are observing also more diligently the
proportion of the mixture. Badly therefore did the unskilful philosophy of
Pliny impose upon Georgius Agricola and the more recent writers, so that
they thought the loadstone was wanted by glass-makers on account of its
magnetick strength and attraction. But Scaliger in _De Subtilitate ad
Cardanum_, in making diamond attract iron, when he is discussing
magneticks, wanders far from the truth, unless it be that diamond attracts
iron electrically, as it attracts wood, straws, and all other minute bodies
when it is rubbed. Fallopius reckons that quicksilver draws metals by
reason of an occult property, just as a loadstone iron, amber chaff. But
when quicksilver enters metals, it is wrongly called attraction. For metals
imbibe quicksilver, just as clay water; nor do they do this unless they are
touching, for quicksilver does not allure gold or lead to itself from afar,
but they remain motionless in their places.
* * * * *
CHAP. XXXIX.
On Bodies which mutually repel one another.
Writers who have discoursed on the forces of bodies which attract others
have also spoken about the powers of bodies which repel, but especially
those who have instituted classes for natural objects on the basis of
sympathy and antipathy. Wherefore it would seem necessary for us to speak
also about the mutual strife of bodies, so that published errors should not
creep further, and be received by all to the ruin of true philosophy. They
say that, just as like things attract for the sake of preservation, so
unlike and contrary things for the same purpose mutually repel and put one
another to flight. This is evident in the reaction of many things, but it
is most manifest in the case of plants and animals, which attract kindred
and familiar things, and in like manner reject foreign and unsuitable
things. But in other bodies there is not the same reason, so that when they
are separated, they should come together by mutually {113} attracting one
another. Animals take food (as everything which grows), and draw it into
their interior; they absorb the nourishment by certain parts and
instruments (through the action and operation of the _anima_). They enjoy
by natural instinct only the things set in front of them and near them, not
things placed afar off; and this without any alien force or motion.
Wherefore animals neither attract any bodies nor drive them away. Water
does not repel oil (as some think) because the oil floats on water; nor
does water repel mud, because the mud, if mixed in water, settles down in
time. This is a separation of unlike bodies or such as are not perfectly
mixed as respects the material; the separated bodies nevertheless remain
joined without any natural strife. Wherefore a muddy sediment settles
quietly on the bottom of vessels, and oil remains on the top of the water
and is not sent further away. A drop of water remains intact on a dry
surface, and is not expelled from the dry substance. Wrongly therefore do
those who discourse on these matters infer an antipathy (that is, the force
of repelling by contrary passions); for there is no repelling force in
them; and repulsion comes[193] from action, not from passion. But their
greek vocables please them too much. We, however, must inquire whether
there is any body which drives anything else further off without material
impetus, as a loadstone attracts. But a loadstone seems even to repel
loadstone. For the pole of one loadstone repels the pole of another, which
does not agree with it according to nature; by repelling, it turns it round
in an orbit so that they may exactly agree according to their nature. But
if a somewhat weak loadstone, floating freely on water, cannot readily be
turned round on account of impediments, the whole loadstone is repelled and
sent further away from the other. All electricks attract all things: they
never repel or propel anything at all[194]. As to what is related about
certain plants (as about the cucumber, which turns aside when oil is
applied to it), there is a material change from the vicinity, not a hidden
antipathy. But when they show a candle flame put against a cold solid
substance (as iron) turn away to the side, and allege antipathy as the
cause, they say nothing. The reason of this they will see clearer than the
day, when we discourse on what heat is[195]. But Fracastorio's opinion that
a loadstone can be found, which would drive iron away, on account of some
opposing principle lurking in the iron, is foolish.
* * * * *
{115} [Illustration]
BOOK THIRD.
_CHAP. I._
ON DIRECTION.
On referring to the earlier books it will be found shown that a loadstone
has its poles, and that a piece of iron has also poles, and rotation, and a
certain verticity; finally, that the loadstone and the iron direct their
poles toward the poles of the earth. Now, however, we must make clear the
causes of these things and their admirable workings, pointed out indeed
before, but not proven. All those who have written before us about these
rotations have left us their opinions so briefly, so meagrely, and with
such hesitating judgment that they seem hardly likely ever to persuade
anyone, or even to be able to satisfy themselves; and all their petty
reasons are rejected by the more prudent as useless, uncertain, and absurd,
being supported by no proofs or arguments; whence also magnetick science,
being all the more neglected and not understood, has been in exile. The
true austral pole of a loadstone, not the boreal (as all before us used to
think), * if the loadstone is placed in its boat on the surface of water,
turns to the North; in the case of a piece of iron also, whether it has
been excited by a loadstone or not, the southern end moves toward the
North. An oblong piece of iron of three or four digits' length[196], when
skilfully rubbed with a loadstone, quickly turns north and south. Wherefore
mechanicians, taking a piece of iron prepared in this way, balance it on a
pin in a box, and fit it up with the requisites of a sun-dial; or they
prepare the versorium out of two curved pieces of iron with their ends
touching one another, so that the motion may be more constant. In this way
the mariners' versorium is arranged, which is an instrument beneficial,
useful, and auspicious to sailors for indicating, like a good genius,
safety and the right way. But it must be understood on the threshold of
this argument (before we proceed further) that these pointings of the
loadstone or of iron are not perpetually made {116} toward the true poles
of the world, do not always seek those fixed and definite points, or remain
on the line of the true meridian; but usually diverge some distance to the
East or to the West. Sometimes also at certain places on land or sea they
do indicate exactly the true poles. This discrepancy is called the
_Variation_ of the iron or of the loadstone; and since this is brought
about by other causes, and is merely a certain disturbance and perversion
of the true direction, we are directing our attention in this place to the
true direction of the compass and of the magnetick iron (which would be
equally toward the true poles and on the true meridian everywhere on the
earth, unless other obstacles and an untoward pervertency hindered it). Of
its variation and the cause of the perversion we shall treat in the next
book. Those who wrote about the world and about natural philosophy a
century ago, especially those remarkable elementary philosophers, and all
those who trace their knowledge and training to them down to our own times,
those men, I say, who represented the earth as always at rest and, as it
were, a useless weight, placed in the centre of the universe at an equal
distance from the sky on every side, and its nature to be simple, imbued
only with the qualities of dryness and cold, sought diligently for the
causes of all things and of all effects in the heavens, the stars, the
planets, in fire, air, waters and substances of mixed natures. Never indeed
did they recognize that the terrestrial globe had, besides dryness and
cold, some special, effective, and predominant properties, strengthening,
directing, and moving the globe itself through its whole mass and its very
deepest vitals; nor did they ever inquire whether there were any such. For
this reason the crowd of philosophizers, in order to discover the reasons
of the magnetical motions, called up causes lying remote and far away. And
one man seems to me beyond all others worthy of censure, Martin Cortes,
who, since there was no cause which could satisfy him in the whole of
nature, dreamed that there was a point of magnetical attraction beyond the
heavens, which attracted iron. Peter Peregrinus thinks that the direction
arises from the poles of the sky. Cardan thought that the turning of iron
was caused by a star in the tail of the Great Bear; Bessard, the Frenchman,
opines that a magnetick turns toward the pole of the zodiack. Marsilius
Ficinus will have it that the loadstone follows its own Arctick pole; but
that iron follows the loadstone, straws amber; whilst this perhaps follows
the Antarctick pole--a most foolish dream. Others have recourse to I know
not what magnetick rocks and mountains. Thus it is always customary with
mortals, that they despise things near home, whilst foreign and distant
things are dear and prized. But we study the earth itself and observe in it
the cause of so great an effect. The earth, as the common mother, has these
causes inclosed in her innermost parts; in accordance with her rule, {117}
position, condition, verticity, poles, æquator, horizons, meridians,
centre, circumference, diameter, and the nature of the whole interior of
her substance, must all magnetical motions be discussed. The earth has been
ordered by the highest Artificer and by nature in such a way that it should
have parts dissimilar in position, bounds of the whole and complete body,
ennobled by certain functions, by which it might itself remain in a
definite direction. For just as a loadstone, when it is floated on water in
a suitable vessel, or is hung by slender threads in the air, by its
implanted verticity conforms its poles to the poles of the common mother in
accordance with magnetick laws; so if the earth were to deviate from its
natural direction and its true position in the universe, or if its poles
were to be drawn aside (if this were possible) toward the sun-rising or the
sun-setting or toward any other points whatsoever in the visible firmament,
they would return again to the north and south by magnetical motion, and
would settle at the same points at which they are now fixed. The reason why
the terrestrial globe seems to remain more steadily with the one pole
toward those parts and directed toward the Cynosure, and why its pole
diverges by 23 degrees 29 minutes, with a certain variation not
sufficiently investigated as yet by Astronomers, from the poles of the
ecliptick, depends on its virtue magnetical. The causes of the precession
of the æquinoxes and the progression of the fixed stars, and of the change,
moreover, in the declinations of the sun and of the tropicks, must be
sought from magnetick influences; so that neither that absurd motion of
trepidation of Thebit Bencora[197], which is at great variance with
observations, nor the monstrous superstructures of other heavens, are any
longer needed. A versatory iron turns to the position of the earth, and if
disturbed ever so often returns always to the same points. For in the far
regions of the north, in a latitude of 70 or 80 degrees (to which at the
milder seasons of the year our sailors are accustomed to penetrate without
injury from the cold); in the regions halfway between the poles; on the
æquator in the torrid zone; and again in all the maritime places and lands
of the south, in the highest latitude which has thus far been reached,
always the iron magnetick finds its way, and points to the poles in the
same manner (excepting for the difference of variation); on this side of
the æquator (where we live), and on the other side to the south, less well
known, but yet in some measure explored by sailors: and always the lily of
the compass points toward the North. This we have had confirmed by the most
eminent captains, and also by very many of the more intelligent sailors.
These facts have been pointed out to me and confirmed by our most
illustrious Sea-god, Francis Drake, and by another circumnavigator of the
globe, Thomas Candish; our terrella also indicates the same thing. This is
demonstrated in the case of the {118} [Illustration] orbicular stone, whose
poles are A and B; an iron wire CD, which is placed upon the stone, always
points directly along the meridian toward the poles AB, whether the centre
of the wire is on the central line or æquator of the stone, or on any other
part situated between the æquator and the poles, as at H, G, F, E. So the
cusp of a versorium on this side of the æquator points toward the north; *
on the other side the cross is always directed toward the south; but the
cusp or lily[198] does not, as some one has thought, turn toward the south
beyond the æquator. Some inexperienced people indeed, who in distant parts
beyond the æquator have seen the versorium sometimes become more sluggish
and less prompt, thought that the distance from the arctick pole or from
the magnetick rocks was the cause of this. But they are very much mistaken;
for it is as powerful[199], and adjusts itself as quickly to the meridian
or to the point of variation in the southern as in the northern parts of
the earth. Yet sometimes the motion appears slower, namely, when the
supporting pin by lapse of time and long voyaging has become somewhat
blunt, or the magnetick iron parts have lost, by age or rust, some of their
acquired vigour. This may also be shown experimentally by the versatory
iron of a small sun-dial placed on a very short pin set perpendicular to
the surface of the stone, for the iron when touched by a loadstone points
toward the poles of the stone and leaves the poles of the earth; for the
general and remoter cause is overcome by the particular and powerful cause
which is so near at hand. Magnetick bodies have of themselves an
inclination toward the position of the earth and are influenced by a
terrella. Two equal stones of equal strength adjust themselves to a
terrella in accordance with magnetick laws. The iron conceives vigour from
the loadstone and is influenced by the magnetical motions. Wherefore true
direction is the motion of a magnetick body in regard to the verticity of
the earth, the natures of both agreeing and working together toward a
natural position and unity. For indeed we have found out at length, by many
experiments and in many ways, that there is a disposing nature, moving them
together by reason of their various positions by one form that is common
{119} to both, and that in all magnetick substances there is attraction and
repulsion. For both the stone[200] and the magnetick iron arrange
themselves by inclination and declination, according to the common position
of their nature and the earth. And the force of the earth by the virtue of
the whole, by attracting toward the poles, and repelling, arranges all
magneticks which are unfixed and loose. For in all cases all magneticks
conform themselves to the globe of the earth in the same ways and by the
same laws by which another loadstone or any magneticks do to a
terrella.[201]
* * * * *
CHAP. II.
The Directive or Versorial Virtue (which we call
verticity): what it is, how it exists in the loadstone;
_and in what way it is acquired when innate._
Directive force, which is also called by us verticity, is a virtue which
spreads by an innate vigour from the æquator in both directions toward the
poles. That power, inclining in both directions towards the termini, causes
the motion of direction, and produces a constant and permanent position in
Nature, not only in the earth itself but also in all magneticks. Loadstone
is found either in veins of its own or in iron mines, when the homogeneous
substance of the earth, either having or assuming a primary form, is
changed or concreted into a stony substance, which besides the primary
qualities of its nature has various dissimilitudes and differences in
different quarries and mines, as if from different matrices, and very many
secondary qualities and varieties in its substance. A loadstone which is
dug out in this breaking up of the earth's surface and of protuberances
upon it, whether formed complete in itself (as sometimes in China) or in a
larger vein, is fashioned by the earth and follows the nature of the whole.
All the interior parts of the earth mutually conspire together in
combination and produce direction toward north and south. But those
magnetical bodies which come together in the uppermost parts of the earth
are not true united parts of the whole, but appendages and parts joined on,
imitating the nature of the whole; wherefore when floating free on water,
they dispose themselves just in the same way as they are placed in the
terrestrial system of nature. We had a large loadstone of twenty pounds *
weight, dug up and cut out of its vein, after we had first observed and
marked its ends; then after it was dug out, we placed it in a boat on
water, so that it could turn freely; then immediately the face which had
looked toward the north in the quarry began to {120} turn to the north on
the waves and at length settled toward that point. For that face which
looked toward the north in the quarry is the southern, and is attracted by
the northern parts of the earth, [Illustration] in the same way as pieces
of iron which acquire their verticity from the earth. About this point we
intend to speak afterwards[202] under change of verticity. But there is a
different rotation of the internal parts of the earth, which are perfectly
united to the earth and which are not separated from the true substance of
the earth by the interposition of bodies as are loadstones in the upper
portion of the earth, which is maimed, corrupt, and variable. Let A B be a
piece of magnetick ore; between which and the uniform globe of the earth
lie various soils or mixtures which separate the ore to a certain extent
from the globe of the true earth. It is therefore influenced by the forces
of the earth just in the same way as C D, a piece of iron, in the air. So
the face B of some ore or of that piece of it is moved toward the Boreal
pole G, just as the extremity C of the iron, not A or D. But the condition
of the piece E F is different, which piece is produced in one connected
mass with the whole, and is not separated from it by any earthy mixture.
For if the part E F were taken out and floated freely in a boat by itself,
it is not E that would be directed toward the Boreal pole, but F. So in
those substances which acquire their verticity in the air, C is the
southern part and is seen to be attracted by the Boreal pole G. In the case
of others which are found in the upper unstable portion of the earth, B is
the south, and in like manner inclines toward the Boreal pole. But if those
pieces deep down which are produced along with the earth are dug up, they
turn about on a different plan. For F turns toward the Boreal parts of the
earth, because * is the southern part; E toward the south, because it is
the northern. So of a magnetick body, C D, placed close to the earth, the
end C turns toward the Boreal pole; of one that is adnate to it B A, B
inclines to the North; of one that is innate in it, E F, E turns toward the
southern pole; which is confirmed by the {121} [Illustration] following
demonstration, and comes about of necessity according to all magnetick
laws. Let there be a terrella with poles A B; from its mass cut out a small
part E F; if this be suspended by a fine thread above the hole or over some
other place, E does not seek the pole A but the pole B, and F turns to A;
very differently from a rod of iron C D; because C, touching some northern
part of the terrella, being magnetically carried away makes a turn round to
A, not to B. And yet here it should be observed, that if the pole A of *
the terrella were moved toward the earth's south, the end E of the piece
cut out by itself, if not brought too near to the stone, would also move of
itself toward the south. But the end C of the piece of iron, placed beyond
its orbe of virtue, will turn toward the north. The part E F of the
terrella, whilst in the mass, produced the same direction as the whole; but
when it is separated and suspended by a thread, E turns to B, and F to A.
[Illustration] {122} So parts having the same verticity with the whole,
when separated, are impelled in the contrary direction; for contrary parts
solicit contrary parts. Nor yet is this a true contrariety, but the highest
concordancy, and the true and genuine conformation of bodies magnetical in
the system of nature, if they shall have been divided and separated: for
the parts thus divided should be raised some distance from the whole, as
will be made clear afterwards. Magnetick substances seek a unity as regards
form; they do not so much respect their own mass. Wherefore the part F E is
not attracted into its former bed; but when once it is unsettled and at a
distance, it is * solicited by the opposite pole. But if the small piece F
E is placed back again in its bed or brought close to, without any
substances intervening, it acquires its former combination, and, as a part
of the whole once more united, accords with the whole and sticks readily in
its former position; and E remains toward A, and F toward B, and they
settle steadily in their mother's lap. The reasoning is the same when the
stone is divided into equal parts through the poles. [Illustration] A
spherical stone is divided into two equal parts along the axis A B; *
whether therefore the surface A B is in the one part facing upward (as in
the former diagram) or lying on its face in both parts (as in * the
latter), the end A tends toward B. But it must also be understood that the
point A is not carried with a definite aim always toward the point B,
because in consequence of the division the verticity proceeds to other
points, as to F G, as appears in the fourteenth chapter of this book. And L
M are now the axes in each, and A B is no longer the axis; for magnetick
bodies, as soon as they are divided, become single magnetick wholes; and
they have {123} vertices in accordance with their mass, new poles arising
at each end in consequence of the division. Yet the axis and the poles
always follow the leading of a meridian; because that force passes along
the meridians of the stone from the æquator to the poles, by an everlasting
rule, the inborn virtue of the substance agreeing thereto from the long and
lasting position and the facing of a suitable substance toward the poles of
the earth; by whose strength continued through many centuries it has been
fashioned; toward fixed and determined parts of which it has remained since
its origin firmly and constantly turned.
* * * * *
CHAP. III.
How Iron acquires Verticity through
a Loadstone, and how that verticity
_is lost and changed_.
Friction between an oblong piece of iron and a loadstone imparts to the
former magnetick virtues, which are not corporeal nor inherent and
persistent in any body, as we showed in the discussion on coition. It is
plain that the iron, when it has been rubbed hard with one end and applied
to the stone for a pretty long time, receives no stony nature, acquires no
weight; for if, before the iron is touched by the stone, you weigh * it in
a small and very exact goldsmith's balance, you will see after the rubbing
that it has exactly the same weight, neither diminished nor increased. But
if you wipe the iron with cloths after it has been touched, or wash it in
water, or scour it with sand or on a grindstone, still it in nowise lays
aside its acquired strength. For the force is spread through the whole body
and conceived in the inmost parts, and cannot in any way be washed or wiped
away. Let an experiment then be made in fire, that untamed tyrant of
nature. Take a piece of iron of the length of a palm and the thickness of a
goosequill pen; let this iron be passed through a suitable round cork and
placed on the surface of water, and observe the end which turns to the
north; rub this particular end with the true southern end of a loadstone;
the iron so rubbed turns toward the south. Remove the cork, and place the
end * which was excited in the fire until the iron is just red-hot; when it
is cooled, it will retain the strength of the loadstone and the verticity,
though it will not be so prompt, whether because the force of the fire had
not yet continued long enough to overcome all its {124} strength, or
because the whole iron was not heated to redness, for the virtue is
diffused through the whole. Remove the cork a second time, and putting the
whole iron in the fire, blow the fire with the bellows, so that it may be
all aglow, and let it remain a little longer time red-hot; when cooled (so,
however, that, whilst it is cooling, it does not rest in one position),
place it again on the water with the cork, and you will see that it has
lost the verticity * which it had acquired from the stone. From these
experiments it is clear how difficult it is for the property of polarity
implanted by the loadstone to be destroyed. But if a small loadstone had
remained as long in the same fire, it would have lost its strength. Iron,
because it does not so easily perish, and is not so easily burnt up as very
many loadstones, retains its strength more stably, and when it is lost can
recover it again from a loadstone; but a loadstone when burnt does not
revive. But now that iron, which has * been deprived of its magnetick form,
moves in a different way from any other piece of iron, for it has lost its
polar nature; and whereas before the touch of the loadstone it may have had
a motion toward the north, and after contact toward the south; now it turns
to no definite and particular point; but afterwards, very slowly and after
* a long time, it begins to turn in a doubtful fashion toward the poles of
the earth (having acquired some power from the earth). I have said that the
cause of direction was twofold, one implanted in the stone and iron, but
the other in the earth, implanted by the disponent virtue; and for that
reason (the distinction of poles and the verticity in the iron having now
been destroyed) a slow and weak directive power is acquired anew from the
verticity of the earth. We may see, therefore, with what difficulty and
only by the application of hot fires and by long ignition of the iron
heated to softness, the imparted magnetick virtue is eradicated. When this
ignition has overcome the acquired polarity, and it has been now completely
subdued and not awakened again, that iron is left unsettled and utterly
incapable of direction. But we must further inquire how iron remains
affected by verticity. It is manifest that it strongly affects and changes
the nature of the iron, because the presence of a loadstone attracts the
iron to itself with an altogether wonderful readiness. Nor is it only the
part that is rubbed, but on account of the rubbing (on one end only) the
whole iron is affected together, and gains by it a permanent though an
unequal power. This is demonstrated as follows. Rub an iron wire on the end
so * that it is excited, and it will turn towards the north; afterward cut
off some portion of it; you will see that it still turns toward the north
(as before), but more feebly. For it must be understood that the loadstone
excites a steady verticity in the whole iron (if the rod be not too long)
more vigorous throughout the whole mass in a shorter bar, and as long as
the iron remains touching the loadstone a little {125} stronger. But when
the iron is separated from contact with it, then it becomes much weaker,
especially in the end that was not touched. Just as a long rod, one end of
which is placed in the fire and heated, grows exceedingly hot at that end,
less so in the parts adjoining and in the middle, whilst at the other end
it can be held in the hand, and that end is only warm; so the magnetical
vigour diminishes from the excited end to the other end; but it is present
there instantly, and does not enter after an interval of time nor
successively, as the heat in the iron; for as soon as a piece of iron has
been touched by a loadstone it is excited throughout its whole length. For
the sake of experiment, let there be a rod of iron 4 or * 5 digits long,
untouched by a loadstone; as soon as you touch one end only with a
loadstone, the opposite end immediately, or in the twinkling of an eye, by
the power that it has conceived, repels or attracts a versorium, if it be
applied to it ever so quickly.
* * * * *
CHAP. IIII.
Why Iron touched by a Loadstone acquires an opposite
_verticity, and why iron touched by the true Northern side of a stone_
turns to the North of the earth, by the true Southern side
_to the South; and does not turn to the South when rubbed
by the Northern point of the stone, and when by
the Southern to the North, as all who have
written on the loadstone have
falsely supposed._
Demonstration has already been given that the northern part of a loadstone
does not attract the northern part of another stone, but the southern, and
repels the northern part of another stone from its northern side when it is
applied[203] to it. That general magnet, the terrestrial globe, disposes
iron touched by a loadstone in the same way, and likewise magnetick iron
stirs this same iron by its implanted strength, and excites motion and
controls it. For whether the comparison and experiment has been made
between loadstone and loadstone, or loadstone and iron, or iron and iron,
or the earth and loadstone, or the earth and iron conformed * by the earth
or strengthened by the power of a loadstone, the strength and inclinations
of each must mutually harmonize and accord in the same way. But the reason
must be sought, why a piece of iron when touched by a loadstone acquires a
disposition to motion toward the opposite pole of the earth, and not toward
that {126} pole of the earth to which that pole of that loadstone turned by
which it was excited. It has been pointed out that iron and loadstone are
of one primary nature; when the iron is joined to the loadstone, they
become, as it were, one body, and not only is the end of the iron changed,
but the remaining parts also are affected along with it. A, the north pole
of a loadstone, is placed against the cusp of a piece of iron; the cusp of
the iron has now become the southern part of the iron, [Illustration]
because it is touching the northern part of the stone; the cross-end of the
iron has become the northern. For if that contiguous magnetick substance be
separated from the pole of the terrella, or from the parts near the pole,
the one end (or the end which, whilst the connection was kept up, was
touching the northern part of the stone) is the southern, whilst the other
is the northern. So also if a versorium excited by a loadstone be divided
into ever so many parts (however small), those parts when separated will,
it is clear, arrange themselves in the same disposition as that in which
they were disposed before, when they were undivided. Wherefore whilst the
cusp remains over the northern pole A, it is not the southern end, but is,
as it were, part of a whole; but when it is taken away from the stone, it
is the southern end, because when rubbed it tended toward the northern
parts of the stone, and the cross (the other end of the versorium) is the
northern end. The loadstone and the iron make one body; B is the south pole
of the whole; C (that is, the cross) is the northern end of the whole;
divide the iron also at E, and E will be the southern end with respect to
the cross; and E will likewise be the northern end in respect to B. A is
the true northern pole of the stone and is attracted by the southern pole
of the earth. The end of the iron which is touched by the true boreal part
of the stone becomes the southern end, and turns to A, the north [pole] of
the stone, if it be near; or if it be some distance from the stone it turns
to the north [pole] of the earth. So always iron which is touched (if it is
free and unrestrained) tends to the opposite part of the earth from that
part to which the loadstone that touched it tends. Nor does it * make any
difference how it is rubbed, whether straight up or slanting in some way.
For in any case the verticity flows into the iron, {127} [Illustration]
provided it is touched by either end. Wherefore all the cusps at B acquire
the same verticity, after they are separated, but opposite to that pole of
the stone; wherefore also they are united to the loadstone at the pole B;
and all the crosses in the present figure have the opposite verticity to
the pole E, and are moved and laid hold of by E when they are in a
convenient position. It is exactly the same in the case of the long stone F
H divided at G; F and H always move, both in the whole and in the divided
stone, to opposite poles of the earth, and O and P mutually attract one
another, the one of them being the northern, the other the southern. For,
supposing H to have been the southern in the whole stone and F the
northern, P will be the northern with respect to H in the divided stone,
and O the southern with respect to F. So also F and H mutually incline to a
connection, if they are turned a very little toward one another, and run
together at length and join. But supposing the division of the stone to
have been meridional (that is, according to the line of a meridian, not of
any parallel circle), then they turn [Illustration] round, and A attracts
B, and the end B is attracted to A and attracts A, until, being turned
round, they are connected and cemented together; because magnetick
attraction is not made along the parallels, but meridionally. For this
reason pieces of iron placed on a terrella whose poles are A B, near the
æquator along parallels, * do not combine or stick together firmly: {128}
[Illustration] But if applied to one another along a meridian they are
immediately * joined firmly together, not only on and near the stone, but
even at some distance within the force of the controlling orbe. Thus they
are joined and cemented together at E, but not at C in the other figure.
For the opposite ends C and F meet and adhære together in the case of the
iron just in the same way as A and B before in the case of the stone. But
they are opposite ends, because the pieces of iron proceed from the
opposite sides and poles of the terrella; and C in reference to the
northern pole A is southern, and F is boreal in reference to the * southern
pole B. In like manner also they are cemented together, if the rod C (being
not too long[204]) be moved further toward A, and F toward B, and they be
joined together over the terrella, like A and B of the divided stone above.
But now if the cusp A, * which has been touched by a loadstone, be the
southern end, and you were to touch and rub with this the cusp of another
iron needle B, which has not been touched, B will be northern, and will
point to the south. But if you were to touch with the northern point B any
other iron needle, still new, on its cusp, this again will be southern, and
will turn to the north. The iron not only receives the necessary strength
from the loadstone, if it be a good loadstone, but also imparts its
acquired strength to another piece of iron, and the second to a third
(always in strict accordance with magnetick laws). In all these
demonstrations of ours it should always be borne in mind that the poles of
a stone, as well as those of iron, whether touched or untouched, are always
in fact and by nature opposite to the pole toward which they point and are
so designated by us, as we have laid down above. For in them all it is
always the northern * which tends to the south, either of the earth or of
the stone, and the southern which tends to the north of the stone. Northern
parts are attracted by the southern of the earth; so in the boat they {129}
tend toward the south. A piece of iron touched by the northern parts of a
loadstone becomes south at the one end and tends always (if it is near and
within the orbe of the loadstone) to the north of the stone, and if it be
free and left to itself at some distance from the stone, it tends to the
northern part of the earth. The northern pole A of a loadstone turns to G,
the south of the earth; a versorium touched at its cusp by the part A
follows A, because it has become southern. But the versorium C, placed
farther away from the loadstone, turns its cusp to F, the north of the
earth, because * the cusp has become southern by contact with the boreal
part of the stone. So the ends touched by the northern part of the stone
are made southern, or are excited with a southern polarity, and tend toward
the north of the earth; those touched by the southern pole are made
northern, or are excited with a northern force, and turn to the south of
the earth.
[Illustration]
* * * * *
CHAP. V.
On the Touching of pieces of Iron
_of divers shapes._
Bars of iron, when touched by a loadstone, have one end north, the other
south, and in the middle is the limit of verticity, like the æquinoctial
circle on the globe of a terrella or on an iron globe. But when an iron
ring is rubbed on one side on a * loadstone, then the one pole is on the
place that was in contact, whilst the other is at the opposite point; and
the magnetick power divides the ring into two parts by a natural
distinction which, though not in shape, yet in power and effect is like an
æquator. But if a thin straight rod be bent into a ring without any welding
or union of the ends, and be touched in the middle by a loadstone, both
ends will be of the same verticity. Let a ring be taken which is whole and
continuous, and which has been * touched by a loadstone at one place, and
let it be divided afterward {130} at the opposite point and straightened
out, both ends will also be * of the same verticity, no otherwise than a
thin rod touched in the middle or a ring not cohærent at the joint.
* * * * *
CHAP. VI.
What seems an Opposing Motion in Magneticks
_is a proper motion toward unity_.
[Illustration]
In things magnetical nature always tends to unity, not merely to confluence
and agglomeration, but to harmony; in such a way that the rotational and
disponent faculty should not be disturbed, as is variously shown in the
following example. Let C D be an entire body of some magnetick substance,
in which C tends to B, the north of the earth, and D to the south, A.
Then[205] divide it in the middle in its æquator, and it will be E that is
tending toward A, and F tending toward B. For just as in the undivided
body, so in the divided, nature aims at these bodies being united; the end
E again joins with F harmoniously and * eagerly and they stick together,
but E is never joined to D, nor F to C; for then C must be turned contrary
to nature toward A, the south, or D toward B, the north, which is foreign
to them and incongruous. Separate the stone in the place where it is cut
and turn D round to C; they harmonize and combine excellently. For D is
tending to the south, as before, and C to the north; E and F, parts which
were cognate in the ore, are now widely separated, for they do not move
together on account of material affinity, but they take their motion and
inclination from their form. So the ends, whether joined or divided, tend
magnetically in the same way to the earth's poles in the first figure where
there is one whole, or divided as in the second figure; and F E in the
second figure is a perfect magnetick joined together into one body and C D,
just as it was primarily produced in its ore, and F E in its boat, turn in
{131} this way to the poles of the earth and are conformed to them. * This
harmony of the magnetick form is shown also in the forms of vegetables. Let
A B be a twig from a branch of osier or other * tree which sprouts easily.
Let A be the upper part, B the lower part toward the root; divide it at C
D; I say that the end D, if grafted again to C by the primer's art, grows
to it; just as also if B is grafted to A, they grow together and germinate.
But D being grafted on A, or C on B, they are at variance, and never grow
into one another, but one of them dies on account of the inverted and
inharmonious arrangement, since the vegetative force, which moves in one
way, is now impelled in opposite directions.
[Illustration]
* * * * *
CHAP. VII.
A determined Verticity and a disponent Faculty are what
arrange magneticks, not a force, attracting or pulling them
_together, nor merely strongish coition or unition_.
[Illustration] {132}
In the neighbourhood of the æquinoctial A there is no coition of the ends
of a piece of iron with the terrella; at the poles there is the strongest.
The greater the distance from the æquinoctial, the stronger is the coition
with the stone itself, and with any part of it, not with its pole alone.
Yet pieces of iron are not raised up on account of some peculiar attracting
force or a stronger combined force, but on account of that common directing
or conforming and rotating force; nor indeed is a spike in the part about
B, even one that is very small and of no * weight[206], raised up to the
perpendicular by the strongest terrella, but cleaves to it obliquely. Also
just as a terrella attracts magnetick bodies variously with dissimilar
forces, so also an iron snout placed on the stone obtains a different
potency in proportion to the latitude, * just as a snout at L by its firmer
connection resists a greater weight more stoutly than one at M, and at M
than at N. But neither does the snout raise the spike to the perpendicular
except at the poles, as is shown in the figure. A snout at L may hold and
lift from the earth two ounces of iron in one piece; yet it is not strong
enough to raise an iron wire of two grains weight to the perpendicular,
which would happen if the verticity arose on account of a * stronger
attraction, or rather coition or unition.
* * * * *
CHAP. VIII.
Of Discords between pieces of Iron upon the same pole
of a loadstone, and how they can agree and
_stand joined together_.
Suppose two iron wires or a pair of needles stuck on the pole of a
terrella; though they ought to stand perpendicularly, they mutually repel
one another at the upper * end, and produce the appearance of a fork; and
if one end be forcibly impelled toward the other, the other declines and
bends away from association with it, as in the following figure.
[Illustration] {133} A and B, iron spikes, adhære obliquely[207] upon the
pole on account of their nearness to one another; either alone would
otherwise stand erect and perpendicular. For the extremities A B, being of
the same verticity, mutually abhor and fly one another. For if C be the
northern pole of the terrella, A and B are also northern ends; but the ends
which are joined to and held at the pole C are both * southern. But if
those spikes be a little longer (as, for example, of two digits length) and
be joined by force, they adhære together and unite in a friendly style, and
are not separated without force. For they are magnetically welded, and
there are now no longer two distinct ends, but one end and one body; no
less than a wire which is doubled and set up perpendicularly. But here is
seen also another subtile point, that if those spikes were shorter, not as
much as the * breadth of one digit, or even the length of a barleycorn,
they are in no way willing to harmonize or to stand straight up at the same
time, because naturally in shorter wires the verticity is stronger in the
ends which are distant from the terrella and the magnetick discord more
vehement than in long ones. Wherefore they in no way admit of an intimate
association and connection.
[Illustration]
Likewise if those lighter pieces of iron or iron wires be suspended,
hanging, as A and B, from a very fine silk thread, not twisted * but
braided, distant from the stone the length of a single barleycorn, then the
opposing ends, A and B, being situated within the orbe of virtue above the
pole, keep a little away from one another for the same reason; except when
they are very near the pole of the stone C, the stone then attracting them
more strongly toward one end.
* * * * *
{134} CHAP. IX.
Figures illustrating direction and showing varieties
_of rotations_.
[Illustration]
Passing from the probable cause of motion toward fixed points (according to
magnetick laws and principles), it remains for us to indicate those
motions. Above a round loadstone (whose poles are A, B) let a versatory
needle be placed whose cusp has been excited by the pole A; that cusp is
certainly directed toward A, and is strongly attracted by A; because,
having been touched by A, it is in true harmony with A, and combines with
it; and yet it is called contrary, because when the versorium is separated
from the stone, it is seen to be moved toward the opposite part of the
earth to that toward which the pole A of the loadstone is moved. For if A
be the northern pole of the terrella, the cusp is the southern end of the
needle, of which the other end (namely, the cross) is pointed to B; so B is
the southern pole of the loadstone, but the cross is the northern end of
the versorium. So also the cusp is attracted by E, F, G, H, and by every *
part of a meridian, from the æquator toward the pole, by the faculty
disponent; and when the versorium is on the same parts of the meridian, the
cusp is directed toward A. For it is not the point A that turns the
versorium toward it, but the whole loadstone; as also the whole earth does,
in the turning of loadstones to the earth.
[Illustration]
_Figures illustrating magnetick directions in a right sphere[208] of stone,
and in the right sphere of the earth, as well as the polar directions to
the perpendicular of the poles._ All these cusps have been touched by the
pole A; all the cusps are turned toward A, excepting that one which is
repelled by B.
{135}
[Illustration] _Figures illustrating horizontal directions above the body
of a loadstone._ All the cusps that have been made southern by rubbing on
the boreal pole, or some place round the northern pole A, turn toward the
pole A, and turn away from the southern pole B, toward which all the
crosses look. I call the direction horizontal, because it is arranged along
the plane of the horizon; for nautical and * horological instruments are so
constructed that the iron hangs or is supported in æquilibrium on the point
of a sharp pin, which prevents the dipping of the versorium, about which we
intend to speak later. And in this way it is of the greatest use to man,
indicating and distinguishing all the points of the horizon and the winds.
Otherwise on every oblique sphere (whether of stone or the earth) versoria
and all magnetick substances would have a dip by their own nature below the
horizon; and at the poles the directions would be perpendicular, which
appears in our discussion _On Declination_.
[Illustration]
_A round stone (or terrella) cut in two at the æquator;_ and all the cusps
have been touched by the pole A. The points at the centre of the earth, and
between the two parts of the terrella which has been cut in two through the
plane of the æquator, {136} are directed as in the present[209] diagram.
This would also happen in the same way if the division of the stone were
through the plane of a tropick, and the mutual separation of the divided
parts and the interval between them were the same as before, when the
loadstone was divided through the plane of the æquator, and the parts
separated. For the cusps are repelled by C, are attracted by D; and the
versoria are parallel, the poles or the verticity in both ends mutually
requiring it.
[Illustration]
_Half a terrella by itself and its directions, unlike the directions * of
the two parts close to one another as shown in the figure above_. All the
cusps have been touched by A; all the crosses below except the middle one
tend toward the loadstone, not straight, but obliquely; because the pole is
in the middle of the plane which before was the plane of the æquator. All
cusps touched by places distant from the pole move toward the pole (exactly
the same as if they had been rubbed upon the pole itself), not toward the
place where they were rubbed, wherever that may have been in the undivided
stone in some latitude between the pole and the æquator. And for this
reason there are only two distinctions of regions, northern and southern,
in the terrella, just {137} as in the general terrestrial globe, and there
is no eastern nor western place; nor are there any eastern or western
regions, rightly speaking; but they are names used in respect of one
another toward the eastern or western part of the sky. Wherefore it does
not appear that Ptolemy did rightly in his _Quadripartitum_, making eastern
and western districts and provinces, with which he improperly connects the
planets, whom the common crowd of philosophizers and the superstitious
soothsayers follow.
* * * * *
CHAP. X.
On Mutation of Verticity and of Magnetick
Properties, or on alteration in the power
_excited by a loadstone_.
Friction with a loadstone gives to a piece of iron a verticity strong
enough; not, however, so stable that the iron may not by being rubbed on
the opposite part (not only with a more powerful loadstone, but with the
same) be changed and deprived of all its former verticity, and indued with
a new and opposite one. Take a piece of iron wire and rub each end of the
wire equally with one and the same pole of a loadstone, and let it be
passed through a suitable cork and place it on water. Then truly one end of
the wire will be directed toward that pole of the earth toward which that
end of the stone will not turn. But which end of the iron wire will it be?
That certainly which was rubbed last. Rub the other end of this again with
the same pole, and immediately * that end will turn itself in the opposite
direction. Again touch the former end of the iron wire only with the same
pole of the loadstone as before; and that[210] end, having gained the
command, immediately changes to the contrary side. So you will be able to
change the property of the iron frequently, and that end of the wire rules
which has been touched the last. Now then merely hold the boreal pole of
the stone for some time near the boreal part of the wire which was last
touched, so that it does not touch, but so that it is removed from it by
one, two, or even three digits, if the stone have been pretty * strong; and
again it will change its property and will turn round to the contrary side;
which will also happen (albeit rather more feebly) even if the loadstone be
removed to a distance of four digits. You will be able to do the same
thing, moreover, with both the austral and the boreal part of the stone in
all these experiments. Verticity may likewise be acquired and changed when
thin plates of gold, * silver, and glass are interposed between the stone
and the end of the iron or iron wire, if the stone were rather strong, even
if the {138} intermediate lamina is not touched either by the iron or the
stone. And these changes of verticity take place in smelted iron. Indeed
what the one pole of the stone implants and excites, the other disturbs and
extinguishes, and confers a new force. For it does not require a stronger
loadstone to take away the weaker and sluggish virtue and to implant the
new one; nor is iron inebriated by the equal strength of loadstones, and
made utterly uncertain and neutral, as Baptista Porta teaches; but by one
and the same loadstone, or by loadstones endowed with equal power and
might, its strength is, in accordance with magnetick rules, turned round
and changed, excited, repaired, or disturbed. But a loadstone itself, by
being rubbed on another, whether a larger or a more powerful stone, is not
disturbed from its own property and verticity, nor does it turn round
toward the opposite direction in its boat, or to the other pole opposite to
that to which it inclines by its own nature and implanted verticity. For
strength which is innate and has been implanted for a very long time abides
more firmly, nor does it easily yield from its ancient holding; and that
which has grown for a long time is not all of a sudden brought to nothing,
without the destruction of the substance containing it. Nevertheless in a
long interval of time a change * does take place; in one year, that is to
say, or two, or sometimes in a few months; doubtless when a weaker
loadstone remains lying by a stronger one contrary to the order of nature,
namely, with the northern pole of one loadstone adjoined to the northern
pole of another, or the southern to the southern. For so the weaker
strength gradually declines with the lapse of time.
* * * * *
CHAP. XI.
On the Rubbing of a piece of Iron on a Loadstone
in places midway between the poles, and upon
_the æquinoctial of a terrella_.
Select a piece of iron wire of three digits length, not touched by a
loadstone (but it will be better if its acquired verticity be rather weak
or have been damaged in some way); touch it and rub it on the æquator of a
terrella, exactly on the æquinoctial line in the direction of its length,
on the one end, or the ends only, or in all its parts; place the wire
touched in this * way on water in a cork fitted for it; it will swim about
doubtfully on the waves without any acquired verticity, and the verticity
previously implanted will be disturbed. If, however, it float by chance
toward the poles, it will be checked a little by the poles of the earth,
and will at length by the influence of the earth be indued with verticity.
* * * * *
{139} CHAP. XII.
In what way Verticity exists in any Iron that has
_been smelted though not excited by a lodestone_.
[Illustration]
Having thus far[211] demonstrated natural and inborn causes and powers
acquired by means of the stone, we will now examine the causes of magnetick
virtues in smelted iron that has not been excited by a stone. Loadstone and
iron furnish and exhibit to us wonderful subtilities. It has been
repeatedly shown above that iron not excited by a stone turns north and
south; further that it has verticity, that is, special and peculiar polar
distinctions, just as a loadstone, or iron which has been rubbed upon a
loadstone. This indeed seemed to us at first wonderful and incredible; the
metal of iron from the mine is smelted in the furnace; it runs out of the
furnace, and hardens into a great mass; this mass is divided in great
worksteads, and is drawn into iron bars, from which smiths again construct
many instruments and necessary pieces of iron-work. Thus the same mass is
variously worked up and transformed into very many similitudes. What is it,
then, which {140} preserves its verticity, and whence is it derived? So
take this first from the above[212] smithy. Let the blacksmith beat out
upon his anvil a glowing mass of iron of two or three ounces weight into an
iron spike of the length of a span of nine inches. Let the smith be
standing with his face to the north, his back to the south, so that * the
hot iron on being struck has a motion of extension to the north; and let
him so complete his work with one or two heatings of the iron (if that be
required); let him always, however, whilst he is striking the iron, direct
and beat out the same point of it toward the north, and let him lay down
that end toward the north. Let him in this way complete two, three, or more
pieces of iron, nay, a hundred or four hundred; it is demonstrable that all
those which are thus beaten out toward the north, and so placed whilst they
are cooling, turn round on their centres; and floating pieces of iron
(being transfixed, of course, through suitable corks) make a motion in the
water, the determined end being toward the north. In the same way also
pieces of iron acquire verticity from their direction whilst they are being
beaten out and hammered or drawn out, * as iron wires are accustomed to do
toward some point of the horizon between east and south or between south
and west, or in the opposite direction. Those, however, which are pointed
or drawn out rather toward the eastern or western point, conceive * hardly
any verticity or a very undecided one. That verticity is especially
acquired by being beaten out. But a somewhat inferior iron ore, in which no
magnetick powers are apparent, if put in a * fire (its position being
observed to be toward the poles of the world or of the earth) and heated
for eight or ten hours, then cooled away from the fire, in the same
position towards the poles, acquires a verticity in accordance with the
position of its heating and cooling. Let a rod of cast iron be heated
red-hot in a strong fire, in which it lies * meridionally (that is, along
the path of a meridian circle), and let be removed from the fire and
cooled, and let it return to its former temperature, remaining in the same
position as before; then from this it will turn out that, if the same ends
have been turned to the same poles of the earth, it will acquire verticity,
and the end which looked toward the North on water with a cork before the
heating, if it have been placed during the heating and cooling toward the
fourth, now turns round to the south. But if perchance sometimes the
rotation have been doubtful and somewhat feeble, let it be placed again in
the fire, and when it is taken out at a red heat, let it be perfectly
cooled toward the pole from which we desire the verticity, and the
verticity will be acquired. Let the same rod be heated * in the contrary
position, and let it be placed so at a red heat it is cool; for it is from
its position in cooling (by the operation of the verticity of the earth)
that verticity is put into the iron, and it turns round to parts contrary
to its former verticity. So {141} the end which formerly looked toward the
north now turns to the south. In accordance with these reasonings and in
these ways the boreal pole of the earth gives to the end of a piece of iron
turned toward it a southern verticity, and that end is attracted by that
pole. * And here it must be observed that this happens to iron not only
when it is cooled in the plane of the horizon, but also at any angle to it
almost up to the perpendicular toward the centre of the earth. So the
heated iron conceives vigour and verticity from the earth more quickly in
the course of its return to its normal state, and in its recovery, as it
were (in the course of which it is transformed), than by its mere position
alone. This is effected better and more * perfectly in winter and in colder
air, when the metal returns more certainly to its natural temperature, than
in summer and in warm regions. Let us see also what position alone and a
direction toward the poles of the earth can effect by itself without fire
and heat. Iron rods which have been placed and fixed for a long time,
twenty * or more years, from south to north (as they not infrequently are
fixed in buildings and across windows), those rods, I say, by that long
lapse of time acquire verticity and turn round, whether hanging in the air,
or floating (being placed on cork), to the pole toward which they were
pointing, and magnetically attract and repel a balanced iron magnetick; for
the long continued position of the body toward the poles is of much avail.
This fact (although conspicuous by manifest experiments) is confirmed by an
incident related in an Italian letter[213] at the end of a book of Maestro
Filippo Costa, of Mantua, _Sopra le Compositioni degli Antidoti_ written in
Italian, which translated runs thus: "A druggist of Mantua showed me a
piece of iron entirely changed into a magnet, drawing another piece of iron
in such a way that it could be compared with a loadstone. Now this piece of
iron, when it had for a long time held up a brick ornament on the top of
the tower of the church of St. Augustine at Rimini, had been at length bent
by the force of the winds, and remained so for a period of ten years. When
the monks wished to bend it back to its former shape, and had handed it
over to a blacksmith, a surgeon named Maestro Giulio Caesare discovered
that it was like a magnet and attracted iron." This was caused by the
turning of its extremities toward the poles for so long a time. And so what
has been laid down before about change of verticity should be borne in
mind; how in fact the poles of iron spikes are altered, when a loadstone is
placed against them only with its pole and points toward them, even at a
rather long distance. Clearly it is in the same way that that large magnet
also (to wit, the earth itself) affects a piece of iron and changes its
verticity. For, although the iron may not touch the pole of the earth, nor
any magnetick part of the earth, yet verticity is acquired and changed; not
because the poles of the earth and the point itself which is 39° distant
{142} from our city of London, changes the verticity at a distance of so
many miles; but because the whole magnetick earth, that which projects to a
considerable height, and to which the iron is near, and that which is
situated between us and the pole, and the vigour existing within the orbe
of its magnetick virtue (the nature of the whole conspiring thereto),
produces the verticity. For the magnetick effluence of the earth rules
everywhere within the orbe of its virtue, and transforms bodies; but those
things which are more similar to it, and specially connected with it by
nature, it rules and controls; as loadstone and iron. Wherefore in very
many matters of business and actions it is clearly not superstitious and
idle to observe the positions and conditions of lands, the points of the
horizon and the places of the stars. For as when a babe is brought forth
into the light from its mother's womb, and acquires respiration and certain
animal activities, then the planets and celestial bodies[214], according to
their position in the universe, and according to that configuration which
they have with regard to the horizon and the earth, instil peculiar and
individual qualities into the newly born; so that piece of iron, whilst it
is being formed and lengthened out, is affected by the common cause (to
wit, the earth); whilst it is returning also from its heated condition to
its former temperature, it is imbued with a special verticity in accord
with its position. Rather long pieces of iron sometimes have the same
verticity * at each end; wherefore they have motions which are less certain
and well ordered on account of their length and of the aforesaid processes,
exactly as when an iron wire four feet long is rubbed at each end upon the
same pole of a loadstone.
* * * * *
CHAP. XIII.
Why no other Body, excepting a magnetick, is imbued
_with verticity by being rubbed on a loadstone; and why no_
body is able to instil and excite that virtue,
_unless it be a magnetick._
Ligneous substances floating on water never by their own strength turn
round toward the poles of the earth, save by chance. So wires of gold,
silver, brass, tin, lead, or glass, pushed through corks and floating, have
no sure direction; and for this reason they do not show poles or points of
variation when rubbed with a loadstone. For those things which do not of
themselves incline toward the poles and obey the earth are also not ruled
by {143} the touch of a loadstone; for the magnetick vigour has no entrance
into their inward parts; neither is the magnetick form received by them,
nor are their forms magnetically excited; nor, if it did enter, would it
effect anything, because in those bodies (mixed up with various kinds of
efflorescent humours and forms, corrupted from the original property of the
earth) there are no primary qualities. But those prime qualities of iron
are excited by the juxtaposition of a loadstone, just as brute animals or
men, when they are awakened out of sleep, move and put forth their
strength. Here one must marvel at a demonstrable error of B. Porta, who,
while rightly opposing a very old falsehood about the diamond, in speaking
of a power contrary to that of the loadstone, introduces another still
worse opinion; that forsooth iron, when touched by a diamond, turns to the
north. "If" (he says) "you rub a steel-Needle on a Diamond, and then put it
in a Boat, or thrust it through a reed, or hang it up by a Thread, it will
presently turn to the North, almost as well as if it had been touched with
the Loadstone; but something more faintly. And, what is worth noting, the
contrary part will turn the iron to the South: and when I had tried this in
many steel-Needles, and put them all into the Water, I found, that they all
stood equi-distant, pointing to the North." This indeed would * be contrary
to our magnetick rules. For this reason we made an experiment with seventy
excellent diamonds, in the presence of many witnesses, on a large number of
spikes and wires, with the most careful precautions, floating (thrust, of
course, through their corks) on the surface of water; never, however, could
we observe this. He was deceived by the verticity acquired from the earth
(as stated above) in the spike or wire of iron itself, and the iron itself
turned aside to its own definite pole; and he, being ignorant of this,
thought it was done by the diamond. But let the investigators of natural
phenomena take heed that they are not the more deceived by their own badly
observed experiments, and disturb the commonwealth of letters with their
errors and stupidities. Diamond is sometimes designated by the name of
_Sideritis_, not because it is made of iron or because it draws iron, but
on account of its lustre, resembling flashing steel; with such a lustre do
the choicest pieces of diamond shine; hence by very many writers many
qualities are imputed to diamond which really belong to siderite loadstone.
* * * * *
{144} CHAP. XIIII.
The Placing of a Loadstone above or below a magnetick
body suspended in æquilibrium changes neither the power
_nor the verticity of the magnetick body._
Quietly to pass this over would be improper, because a recent error arising
from a defective observation of Baptista Porta must be overthrown; on which
he (by an unfortunate repetition) even writes three chapters, namely, the
18th, the 31st, and the 42nd. For if a loadstone or a piece of magnetick
iron, hanging in æquilibrium or floating on water, is attracted and
disposed toward certain definite points, when you bring above it a piece of
iron or another loadstone, it will not, if you afterward put the same[215]
below it, turn round to the contrary parts; but the same ends of the iron
or the loadstone will always be directed toward the same ends of the stone,
even if the loadstone or the iron is suspended in any way in æquilibrium or
is poised on a needle, so that it can turn round freely. He was deceived by
the irregular shape of some stone, or because he did not arrange the
experiment suitably. Wherefore he is led astray by a vain opinion, and
thinks he may infer that, just as a stone has an arctic and antarctic pole,
so also it has a western and an eastern, and an upper and a lower pole. So
from foolish ideas conceived and admitted arise other fallacies.
* * * * *
CHAP. XV.
The Poles, Æquator, Centre in an entire Loadstone
_remain and continue steady; by diminution and_
separation of some part they vary and
_acquire other positions._
[Illustration] *
Suppose A B to be a terrella, whose centre is E, and whose diameter (as
also its æquinoctial circle) is D F. If you cut off a portion (through the
arctic circle, for example), G H, it is demonstrable that the pole which
was at A now has a position at I. But the centre and the æquinoctial recede
toward B {145} merely so that they are always in the middle of the mass
that is left between the plane of the arctick circle G I H and the
antarctick pole B. Therefore the segment of the terrella comprised between
the plane of the former æquinoctial (that, of course, which was the æquator
before cutting that part away) D E F and the newly acquired æquator M L N
will always be equal to the half of that part which was cut off, G I H A.
[Illustration] * But if the portions have been taken away from the side C
D, the poles and axis will not be in the line A B, but in E F, and the axis
would be changed in the same proportion as the æquator in the former
figure. For those positions of forces and virtues, or rather limits of the
virtues, which are derived from the whole form, are moved forward by change
of quantity and shape; since all these limits arise from the conspiring
together of the whole and of all {146} the parts united; and the verticity
or the pole is not a virtue innate in one part, or in some definite limit,
or fixed in the substance; but it is an inclination of the virtue to that
part. And just as a terrella separated from the earth has no longer the
earth's poles and æquator, but individual ones of its own; so also if it
again be divided, those limits and distinctions of the qualities and
virtues pass on to other parts. But if a loadstone be divided in any way,
either along a parallel, or meridionally, so that by the change of shape
either the poles or the æquator move to other positions, if the part cut
off be merely applied in its natural position and joined to the whole, even
without any agglutination or cementing together, the determining points of
the virtues return again to their former sites, as if no part of the body
had been cut off. When a body is entire, its form remains entire; but when
the body is lessened, a new whole is made, and there arises a new entirety,
determined for every loadstone, however small, even for magnetick gravel,
and for the finest sand.
* * * * *
CHAP. XVI.
If the Southern Portion of a Stone be lessened,
something is also taken away from the power
_of the Northern Portion._
Now although the southern end of a magnetick iron is attracted by a
northern end, and repelled by a southern, yet the southern portion of a
stone does not diminish, but increases the potency of the boreal part.
Wherefore if a stone be cut in two and divided through the arctick circle,
or through the tropick of Cancer or the æquator, the southern portion does
not attract magnetick substances so strongly with its pole as before;
because a new whole arises, and the æquator is removed from its old
position and moves forward on account of that cutting of the stone. In the
former condition, since the opposite portion of the stone increases the
mass beyond the plane of the æquator, it strengthens also the verticity,
and the potency, and the motion to unity.
* * * * *
{147} CHAP. XVII.
On the Use and Excellence of Versoria: and how iron
_versoria used as pointers in sun-dials, and the fine needles_
of the mariners' compass, are to be rubbed, that
_they may acquire stronger verticity._
Versoria prepared by the loadstone subserve so many actions in human life
that it will not be out of place to record a better method of touching them
and exciting them magnetically, and a suitable manner of operating. Rich
ores of iron and such as yield a greater proportion of metal are recognized
by means of an iron needle suspended in æquilibrium and magnetically
prepared; and magnetick stones, clays, and earths are distinguished,
whether crude or prepared. An iron needle (the soul of the mariners'
compass), the marvellous director in voyages and finger of God, one might
almost say, indicates the course, and has pointed out the whole way around
the earth (unknown for so many ages). The Spaniards (as also the English)
have frequently circumnavigated (by an immense circuit) the whole globe by
aid of the mariners' compass. Those who travel about through the world or
who sit at home have sun-dials. A magnetick pointer follows and searches
out the veins of ore in mines. By its aid mines are driven in taking
cities; catapults and engines of war are aimed by night; it has been of
service for the topography of places, for marking off the areas and
position of buildings, and for excavating aqueducts for water under ground.
On it depend instruments designed to investigate its own dip and variation.
When iron is to be quickened by the stone, let it be clean and bright,
disfigured by no rust or dirt, and of the best steel[216]. Let the stone
itself be wiped dry, and let it not be damp with any moisture, but let it
be filed gently with some smooth piece of iron. But the hitting of the
stone with a hammer is of no advantage. By these means let their bare
surfaces be joined, and let them be rubbed, so that they may come together
more firmly; not so that the material substance of the stone being joined
to the iron may cleave to it, but they are rubbed gently together with
friction, and (useless parts being rubbed off) they are intimately united;
whence a more notable [Illustration] virtue arises in the iron that is
excited. A is the best way of touching a versorium when the cusp touches
the pole and faces it; B is a moderately good way, when, though facing it,
it is a little way {148} distant from the pole; also in like manner C is
only moderately good on account of the cusp being turned away from the
pole; D, which is farther distant, is hardly so good; F, which is prepared
crosswise along a parallel, is bad; of no virtue and entirely irresponsive
and feeble is the magnetick index L, which is rubbed along the æquator;
oblique and not pointing towards the pole as G, and oblique, not pointing
toward but turned away from the pole as H, are bad. These have been placed
so that they might indicate the distinct forces of a round stone. But
mechanicians very often have a stone tending more to a cone shape, and more
powerful on account of that shape since the pole, on which they rub their
wires, is at the apex of the projecting part. Sometimes the stone has on
the top and above its own pole an artificial acorn or snout made of steel
for the sake of its power. Iron needles are rubbed on the top of this;
wherefore they turn toward the same pole as if they had been prepared on
that part of the stone with the acorn removed. Let the stone be large
enough and strong; the needle, even if it be rather long, should be
sufficiently thick, not very slender; with a moderate cusp, not too sharp,
although the virtue is not in the cusp itself only, but in the whole piece
of iron. A strong large stone is not unfit for rubbing all needles on,
excepting that sometimes by its strength it occasions some dip and
disturbance in the iron in the case of longer needles; so that one which,
having been touched before, rested in equilibrium in the plane of the
horizon, now when touched and excited dips at one end, as far as the
upright pin on which it turns permits it. Wherefore in the case of longer
versoria, the end which is going to be the Boreal, before it is rubbed,
should be a little lighter, so that it may remain exactly in æquilibrio
after it is touched. But a needle in this way prepared does its * {149}
work worse the farther it is beyond the æquinoctial circle. Let the
prepared needle be placed in its capsule, and let it not be touched by any
other magneticks, nor remain in the near vicinity of them, lest by their
opposing forces, whether powerful or sluggish, it should become uncertain
and dull. If you also rub the other end of the needle on the other pole of
the stone, the needle will perform its functions more steadily, especially
if it be rather long. A piece of iron touched by a loadstone retains the
magnetick virtue, excited in it even for ages[217], firm and strong, if it
is placed according to nature meridionally and not along a parallel, and is
not injured by rust or any external injury from the surrounding medium.
Porta wrongly seeks for a proportion between the loadstone and the iron:
because, he says, a little piece of iron will not be capable of holding
much virtue; for it is consumed by the great force of the loadstone. A
piece of iron receives its own virtue fully, even if it be only of the
weight of one scruple, whilst the mass of the loadstone is a thousand
pounds. It is also useless to make the needle rather flat at the end that
is touched, so that it may be better and more perfectly magnetick, and that
it may best receive and hold certain magnetick particles; since hardly any
part will stick on a sharp point; because he thought that it was by the
adhesion of parts of the loadstone (as it were, hairs) that the influence
is imparted and conserved, though those particles are merely rubbed off by
the rubbing of the iron over the softer stone, and the iron none the less
points toward the North and South, if after it is touched it be scoured
with sand or emery powder, or with any other material, even if by long
rubbing of this kind the external parts of it are lessened and worn away.
When a needle is being rubbed, one should always leave off at the end;
otherwise, if it is rubbed on the loadstone from the point toward the
middle, less verticity is excited in the iron, sometimes none at all, or
very little. For where the last contact is, there is the pole and goal of
verticity. In order that a stronger verticity may be produced in the iron
by rubbing on the loadstone, one * ought in northern lands to turn the true
northern pole of the loadstone toward the highest part of the sky; on this
pole that end of the needle is going to be rubbed, which shall afterwards
turn toward the north of the earth; whilst it will be an advantage for the
other end of the needle to be rubbed on the southern pole of the terrella
turned toward the earth, and this being so excited will incline toward the
south. In southern regions beyond the æquator the plan is just the
contrary. The reason of this dissimilarity is demonstrated, Book II., chap,
xxxiv., in which it is shown (by a manifest combination of a terrella and
the earth) why the poles of a loadstone, for different reasons, are one
stronger than the other. If a needle be touched between the mutually
accordant * poles of two loadstones, equal in power, shape, and mass, no
strength {150} [Illustration] is acquired by the needle. A and B are two
loadstones attracting one another, according to nature, at their dissimilar
ends; C, the * point of a needle touched by both at once, is not excited
(even if those loadstones be connected according to nature), if they are
equal; but if they are not equal, virtue is acquired from the stronger.
When a needle is being excited by a loadstone, begin in the middle, and
draw the needle toward its end; at the end let the application be continued
with a very gentle rubbing around the end for some time; that is to say,
for one or two minutes; do not repeat the motion from the middle to the end
(as is frequently done) for in this way the verticity is injured. Some
delay is desirable, for although the power is imparted instantly, and the
iron excited, yet from the vicinity of the loadstone and a suitable delay,
a more steady verticity arises, and one that is more firmly durable in the
iron. Although an armed stone raises a greater weight of iron than an
unarmed one, yet a needle is not more strongly excited by an armed stone
than by an unarmed one. Let there be two iron wires of the same length,
wrought from the same wire; let one be excited by an armed end, the other
by an unarmed end; it is manifest that the same needles have a beginning of
motion or a sensible inclination at equal distances from the same armed and
unarmed loadstone; this is ascertained by measuring with a longish reed.
But objects which are more powerfully excited move more quickly; those
which are less powerfully excited, more feebly, and not unless brought
rather close; the experiment is made on water with equal corks.
* * * * *
{151} [Illustration]
BOOK FOURTH.
_CHAP. I._
ON VARIATION.
Direction has hitherto been spoken of as if in nature there were no
variation; for in the preceding natural history we wished to omit and
neglect this, inasmuch as in a terrestrial globe, perfect and in every
sense complete, there would be none. Since, however, in fact, the earth's
magnetick direction, owing to some fault and slip, deviates from its right
course and from the meridian, we must extract and demonstrate the obscure
and hidden cause of that variance which has troubled and sore racked in
vain the minds of many. Those who before us have written on the magnetick
movements have made no distinction between direction and variation, but
consider the motion of magnetick iron to be uniform and simple. Now true
direction is the motion of the magnetick body to the true meridian and its
continuance therein with its appropriate ends towards the poles. But it
very often happens at sea and on land that the magnetick iron does not
point to the true pole, and that not only a versorium and magnetick pieces
of iron, and the needle of a compass, or a mariners' compass, but also a
terrella in its boat, as well as * iron ore, iron stones, and magnetick
earths, properly prepared, are drawn aside and deviate towards some point
of the Horizon very near to the meridian. For they with their poles
frequently face termini away from the meridian. This variation {152}
(observed by means of instruments or a nautical variation compass) is
therefore the arc of the horizon between the common point of intersecion of
it with the true meridian, and the terminus of the deflecion on the horizon
or projection of the deviating needle. That arc varies and differs with
change of locality. To the terminus of the variation is commonly assigned a
great circle, called the circle of variation, and also a magnetick meridian
passing through the zenith and the point of variation on the horizon. In
the northern regions of the earth this variation is either from the north
toward the east or from the north toward the west: similarly in the
southern regions it is from the south toward the east or toward the west.
Wherefore one should observe in the northern regions of the earth * that
end of the versorium or compass which turns toward the North; but in the
southern regions the other end looking to the south--which seamen and
sciolists for the most part do not understand, for in both regions they
observe only the boreal lily of the compass (that which faces North). We
have before said that all the motions of the magnet and iron, all its
turning, its inclination, and its settlement, proceed from bodies
themselves magnetical and from their common mother the earth, which is the
source, the propagatrix, and the origin of all these qualities and
properties. Accordingly the earth is the cause of this variation and
inclination toward a different point of the horizon: but how and by what
powers must be more fully investigated. And here we must at the outset
reject that common opinion of recent writers concerning magnetick
mountains, or any magnetick rock, or any phantasmal pole distant from the
pole of the earth, by which the motion of the compass or versorium is
controlled. This opinion, previously invented by others, Fracastorio
himself adopted and developed; but it is entirely at variance with
experience. For in that case in different places at sea and on land the
point of variation would change toward the east or west in proportion and
geometrical symmetry, and the versorium would always respect the magnetick
pole: but experience teaches that there is no such definite pole or fixed
terminus on the earth to account for the variation. For the arcs of *
variation are changed variously and erratically, not only on different
meridians but on the same meridian; and when, according to this opinion of
the moderns, the deviation should be more and more toward the east, then
suddenly, with a small change of locality, the deviation is from the north
toward the west as in the northern regions near Nova Zembla. Moreover, in
the southern regions, and at sea at a great distance from the æquator
towards the antarctick pole, there are frequent and great variations, and
not only in the northern regions, from the magnetick mountains. But the
cogitations of others are still more vain and trifling, such as that of
Cortes about a moving influence beyond all the heavens; that of {153}
Marsilius Ficinus about a star in the Bear; that of Peter Peregrinus about
the pole of the world; that of Cardan, who derives it from the rising of a
star in the tail of the Bear[218]; of Bessardus, the Frenchman, from the
pole of the Zodiack; that of Livio Sanuto from some magnetick meridian;
that of Franciscus Maurolycus from a magnetical island; that of Scaliger
from the heavens and mountains; that of Robert Norman, the Englishman, from
a point respective. Leaving therefore these opinions, which are at variance
with common experience or by no means proved, let us seek the true cause of
the variation. The great magnet or terrestrial globe directs iron (as I
have said) toward the north and south; and excited iron quickly settles
itself toward those termini. Since, however, the globe of the earth is
defective and uneven on its surface and marred by its diverse composition,
and since it has parts very high and convex (to the height of some miles),
and those uniform neither in composition nor body, but opposite and
dissimilar: it comes to pass that the whole of that force of the earth
diverts magnetical bodies in its periphery toward the stronger and more
prominent connected magnetick parts. Hence on the outermost surface of the
earth magnetical bodies are slightly perverted from the true meridian.
Moreover, since the surface of the globe is divided into high lands and
deep seas, into great continental lands, into ocean and vastest seas, and
since the force of all magnetical motions is derived from the constant and
magnetick terrestrial nature which is more prevalent on the greater
continent and not in the aquæous or fluid or unstable part; [219]it follows
that in certain parts there would be a magnetick inclination from the true
pole east or west away from any meridian (whether passing through seas or
islands) toward a great land or continent rising higher, that is, obviously
toward a stronger and more elevated magnetick part of the terrestrial
globe. For since the diameter of the earth is more than 1,700 German miles,
those large lands can rise from the centre of the earth more than four
miles above the depth of the ocean bottom, and yet the earth will retain
the form of a globe although somewhat uneven at the top. Wherefore a
magnetical body is turned aside, so far as the true verticity, when
disturbed, admits, and departs from its right (the whole earth moving it)
toward a vast prominent mass of land as though toward what is stronger. But
the variation does really take place, not so much because of the more
prominent and imperfect terrestrial parts and continent lands as because of
the inæquality of the magnetick globe, and because of the real earth, which
stands out more under the continent lands than under the depths of the
seas. We must see, therefore, how the _apodixis_ of this theory can be
sustained by more definite observations. Since throughout all the course
from the coast of Guinea to Cape Verde, the Canary Isles, and the border of
the kingdom of Morocco, and {154} thence along the coasts of Spain, France,
England, Belgium, Germany, Denmark, and Norway, there lie on the right hand
and toward the east a continent and extensive connected regions, and on the
left extensive seas and a vast ocean lie open far and wide, it is consonant
with the theory (as has been carefully observed by many) that magnetical
bodies should turn slightly to the East from the true pole toward the
stronger and more remarkable elevations of the earth. But it is far
otherwise on the eastern shores of northern America; for from Florida by
Virginia and Norumbega to Cape Race and away to the north the versorium is
turned toward the west. But in the middle spaces, so to speak, as in the
more westerly Azores, it looks toward the true pole. That any magnetick
body turns itself similarly to the same regions of the earth is not,
however, because of that meridian or because of the concordancy of the
meridian with any magnetick pole, as the crowd of philosophizers reckon,
for it is not so throughout the whole of that meridian. For on the same
meridian * near Brazil something very different occurs, as we will show
further on. The variation (cæteris paribus) is always less near the
æquator, greater in higher latitudes, with the limitation that it be not
very near the pole itself. Hence the variation is greater on the coast of *
Norway and Belgium than on the coast of Morocco or Guinea: greater also
near Cape Race than in the harbours of Norumbega or of Virginia. On the
coast of Guinea magnetick implements deviate by a third part of one rumbe
to the East: in Cape Verde Islands by a half: on the coast of Morocco by
two thirds: in England at the mouth of the Thames by a whole rumbe: and at
London by nearly eleven degrees and one third. For indeed the moving
magnetick virtue is stronger in a higher latitude; and the larger regions
extending toward the poles dominate the more, as is easily apparent
anywhere on a terrella. For as in the case of true Direction magnetick
bodies tend toward the pole (namely, toward the stronger end, the whole
earth causing the motion), so also do they incline a little toward the
stronger and higher parts by the action of the whole along with the
conjoint action of iron bodies.
* * * * *
{155} CHAP. II.
That the variation is caused by the inæquality of the
_projecting parts of the earth_.
Demonstration of this may manifestly be made [Illustration] * by means of a
terrella in the following way: let there be a round loadstone somewhat
imperfect in some part, and impaired by decay (such an one we had with a
certain part corroded to resemble the Atlantick or great Ocean): place upon
it some fine iron wire of the length of two barleycorns, as in the
following figure. A B, a Terrella in certain parts somewhat imperfect and
of unæqual virtue on the circumference. The versoria E, F, do not vary, but
look directly to the pole A; for they are placed in the middle of the firm
and sound part of the terrella and somewhat distant from the imperfect
part: that part of the surface which is distinguished by dots and
transverse lines is the weaker. The versorium O also does not vary (because
it is placed in the middle of the imperfect part), but is directed toward
the pole, {156} just as near the western Azores on the earth. The versoria
H and L do vary, for they incline toward the sounder parts very near them.
As this is manifest in a terrella whose surface is sensibly rather
imperfect, so also is it in others whole and perfect, when often one part
of the stone has stronger external parts, which nevertheless do not
disclose themselves manifestly to the senses. In such a terrella the
demonstration of the variation and the discovery of the stronger parts is
on this wise. [Illustration] * Let A be the pole, B the place of the
variation, C the stronger regions; then the horizontal versorium at B
varies from the pole A toward C: so that both the variation is shown and
the stronger places of the loadstone recognized. The stronger surface is
also found by a fine iron wire of the length of two barleycorns: for since
at the pole of the terrella it rears up perpendicularly, but in other
places inclines toward the æquator, if in one and the same parallel circle
it should be more erect in one place than in another; where the wire is
raised more upright, there the part and surface of the terrella is
stronger. Also when the iron wire placed over the pole inclines more to one
part than to another. [Illustration] * {157} Let the experiment be made by
means of a fine iron wire of three digits length placed over the pole A, so
that its middle lies over the pole. Then one end is turned away from B
toward C, and is not willing to lie quietly toward B; but on a terrella
which is perfect[220] all round and even it rests on the pole directed
toward any point of the æquator you please. Otherwise, let there be two *
[Illustration] meridians meeting in the poles A B, let iron wires be reared
just at the ends D and C of the equal arcs D A and C A; then the wire at D
(the stronger region) will be more raised up than that at C, the weaker.
And thus the sounder and stronger part of the loadstone is recognized,
which otherwise would not be perceived by the touch. In a terrella which is
perfect, and even, and similar in all its parts, there is, at equal
distances from the pole, no variation[221]. Variation is shown by means of
a terrella, a considerable part of which, forming a surface a little higher
than the rest, does, although it be not decayed and broken, allure the
versorium from the true * direction (the whole terrella co-operating).
A terrella uneven in surface.
[Illustration] {158} It is shown by a small spike placed over a terrella or
by a small versorium; for they are turned by the terrella toward the mass
that stands out and toward the large eminences. In the same way on the
earth the verticity is perturbed by great continents, which are mostly
elevated above the depths of the seas and make the versorium deviate
sometimes from the right tracks (that is, from the true meridians). On a
terrella it is thus demonstrated: the end of the versorium A is not
directed straight to the pole P, if there be a large protuberance B on the
terrella; so also the cusp C deviates from the pole because of the eminence
F. In the middle between the two eminences the versorium G collimates to
the true pole because, being at equal distances from the two eminences B
and F, it turns aside to neither, but observes the true meridian,
especially when the protuberances are of equal vigour. But the versorium N
on the other side varies from the pole M toward the eminences H, and is not
held back, stopped, or restrained by the small eminence O on the terrella
(as it were, some island of land in the ocean). L, however, being
unimpeded, is directed to the pole M. The variation is demonstrated in
another way on a terrella, just as on the earth. Let A be the pole of the
earth, B the equator, C the parallel circle of latitude of 30 degrees, D a
great eminence spread out toward the pole, E another eminence spread out
from the pole toward the æquator. It is manifest that in the middle of D
the versorium F {159} does not vary; while G is very greatly deflected: but
H very little, because it is further removed from D. Similarly also the
versorium I placed directly toward E does not deviate from the pole: but L
and M turn themselves away from the pole A toward the eminence E.
[Illustration]
* * * * *
CHAP. III.
The variation in any one place
_is constant_.
[Illustration]
Vnless there should be a great dissolution of a continent and a subsidence
of the land such as there was of the region Atlantis of which Plato and the
ancients tell, the variation will continue perpetually immutable; the arc
of the variation remains the same in the same place or region, whether it
be at sea or on land, as in times past a magnetick body has declined toward
the East or the West. The constancy of the variation and the pointing of
the versorium to a definite point on the horizon in individual regions is
demonstrated by a small versorium placed over a terrella the surface of
which is uneven: for it always deviates from the meridian by an equal arc.
It is also shown by the inclination of a versorium toward a second magnet;
although in reality it is by the turning power of the whole, whether in the
earth or in a terrella. Place upon a plane a versorium whose cusp is
directed toward the north A: place beside it a loadstone, B, at such a
distance that the versorium may turn aside toward B to the point C, and not
beyond. Then move the needle of the versorium as often as you will (the box
and the loadstone not being moved), and it will certainly always return to
the point C. In the same manner, if you {160} placed the stone so that it
may be truly directed toward E, the cusp always reverts to E, and not to
any other point of the compass. Accordingly, from the position of the land
and from the distinctive nature of the highest parts of the earth (certain
terrene and more magnetick eminences of the regions prevailing), the
variation indeed becomes definite in one and the same place, but diverse
and unæqual from a change of place, since the true and polar direction
originating in the whole terrestrial globe is diverted somewhat toward
certain stronger eminences on the broken surface.
* * * * *
CHAP. IIII.
The arc of variation is not changed equally
_in proportion to the distance of places_.
In the open sea, when a vessel is borne by a favourable wind along the same
parallel, if the variation be changed by one degree in the course of one
hundred miles, the next hundred miles do not therefore lessen it by another
degree; for the magnetick [needle] varies erratically as respects position,
form, and vigour of the land, and also because of the distance. As, for
example, when a course from the Scilly Isles to Newfoundland has proceeded
so far that the compass is directed to the true pole, then, as the vessel
proceeds, in the first part of the course the variation increases toward
the north-west[222], but rather indistinctly and with small difference:
thence, after an equal distance, the arc is increased in a greater
proportion until the vessel is not far from the continent: for then it
varies most of all. But before it touches actual land or enters port, then
at a certain distance the arc is again slightly diminished. But if the
vessel in its course should decline greatly from that parallel either
toward the south or the north, the magnetick [needle] will vary more or
less, according to the position of the land and the latitude * of the
region. For (cæteris paribus) the greater the latitude the greater the
variation.
* * * * *
{161} CHAP. V.
An island in Ocean does not change the variation[223], as
_neither do mines of loadstone_.
Islands, although they be more magnetick than the sea, yet do not change
the magnetick directions or variations. For since direction is a motion
derived from the power of the whole earth, not from the attraction of any
hill but from the disposing and turning power of the whole; so variation
(which is a perturbation of the direction) is an aberration of the real
turning power arising from the great inequalities of the earth, in
consequence of which it, of itself, slightly diverts movable magneticks
toward those which are the largest and the more powerful. The cause now
shown may suffice to explain that which some so wonder at about the Island
of Elba (and although this is productive of loadstone, yet the versorium
(or mariners' compass) makes no special inclination toward it whenever
vessels approach it in the Tyrrhenian sea); and the following causes are
also to be considered, viz.: that the virtue of smaller magnetick bodies
extends scarcely or not at all of itself beyond their own mines: for
variation does not occur because of attraction, as they would have it who
have imagined magnetick poles. Besides, magnetick mines are only agnate to
the true earth, not innate: hence the whole globe does not regard them, and
magneticks are not borne to them, as is demonstrated by the diagram of
eminences.
* * * * *
CHAP. VI.
That variation and direction arise from the disponent
_power of the earth, and from the natural magnetick tendency_
to rotation, not from attraction, or from coition,
_or from other occult cause_.
Owing to the loadstone being supposed (amongst the crowd of philosophizers)
to seize and drag, as it were, magnetick bodies; and since, in truth,
sciolists have remarked no other forces than those so oft besung of
attractive ones, they therefore deem every motion toward the north and
south to be caused by some alluring and inviting quality. But the
Englishman, {162} Robert Norman, first strove to show that it is not caused
by attraction: wherefore, as if tending toward hidden principles, he
imagined a _point respective_[224], toward which the iron touched by a
loadstone would ever turn, not a _point attractive_; but in this he erred
greatly, although he effaced the former error about attraction. He,
however, demonstrates his opinion in this way:
[Illustration]
Let there be a round vessel filled with water: in the middle of the surface
of the water place a slender iron wire on a perfectly round cork, so that
it may just float in æquilibrium on the water; let the wire be previously
touched by a magnet, so that it may more readily show the point of
variation, the point D as it were: and let it remain on the surface for
some time. It is demonstrable that the wire together with the cork is not
moved to the side D of the vessel: which it would do if an attraction came
to the iron wire by D: and the cork would be moved out of its place. This
assertion of the Englishman, Robert Norman, is plausible and appears to do
away with attraction because the iron remains on the water not moving
about, as well in a direction toward the pole itself (if the direction be
true) as in a variation or altered direction; and it is moved about its own
centre without any transference to the edge of the vessel. But direction
does not arise from attraction, but from the disposing and turning power
which exists in the whole earth, not in the pole or in some other
attracting part of the stone, or in any mass rising above the periphery of
the true circle so that a [Illustration] variation should occur because of
the attraction of that mass. Moreover, it is the directing power of the
loadstone and iron and its natural power of turning around the centre which
cause the motion of direction, and of conformation, in which is included
also the motion of the dip. And the terrestrial pole does not attract as if
the terrene force were implanted only in the pole, for the magnetick force
exists in the whole, although it predominates and excels at the pole.
Wherefore that the cork should rest quiescent in the middle and that the
iron excited by a loadstone should not be moved toward the side of the
vessel are agreeable to and in conformity {163} with the magnetick nature,
as is demonstrated by a terrella: for an iron spike placed on the stone at
C clings on at C, and is not pulled * further away by the pole A, or by the
parts near the pole: hence it persists at D, and takes a direction toward
the pole A; nevertheless it clings on at D and dips also at D in virtue of
that turning power by which it conforms itself to the terrella: of which we
will say more in the part _On Declination_.
* * * * *
CHAP. VII.
Why the variation from that lateral cause is not
_greater than has hitherto been observed, having been_
rarely seen to reach two points of the mariners'
_compass, except near the pole_.
The earth, by reason of lateral eminences of the stronger globe, diverts
iron and loadstone by some degrees from the true pole, or true meridian.
As, for example, with us English at London it varies eleven degrees and
1/3: in some other places the variation is a little greater, but in no
other region is the end of the iron ever moved aside very much more from
the meridian. For as the iron is always directed by the true verticity of
the earth, so the polar nature of the continent land (just as of the whole
terrene globe) acts toward the poles: and even if that mass divert
magnetick bodies from the meridian, yet the verticity of those lands (as
also of the whole earth) controls and disposes them so that they do not
turn toward the East by any greater arc. But it is not easy to determine by
any general method how great the arc of variation is in all places, and how
many degrees and minutes it subtends on the horizon, since it becomes
greater or less {164} from diverse causes. For both the strength of true
verticity of the place and of the elevated regions, as well as their
distances from the given place and from the poles of the world, must be
considered and compared; which indeed cannot be done exactly: nevertheless
by our method the variation becomes so known that no grave error will
perturb the course at sea. If the positions of the lands were uniform and
straight along meridians, and not defective and rugged, the variations near
lands would be simple; such as appear in the following figure.
[Illustration]
This is demonstrated by a long loadstone the poles of which are in the ends
A B; let C D be the middle line and the æquinoctial, and let G H and E F
(the lines) be for meridians on which versoria are disposed, the variations
of which are greater at a greater distance from the æquator. But the
inequalities of the maritime parts of the habitable earth, the enormous
promontories, the very wide gulfs, the mountainous and more elevated
regions, render the variations more unequal, or sudden, or more obscure;
and, moreover, less certain and more inconstant in the higher latitude.
* * * * *
{165} CHAP. VIII.
On the construction of the common mariners'
compass[225], and on the diversity of the compasses
_of different nations_.
In a round[226] hollow wooden bowl, all the upper part of which is closed
with glass, a versorium is placed upon a rather long pin which is fixed in
the middle. The covering prevents the wind, and the motion of air from any
external cause. Through the glass everything within can be discerned. The
versorium is circular, consisting of some light material (as card), to the
under part of which the magnetick pieces of iron are attached. On the upper
part 32 spaces (which are commonly called _points_) are assigned to the
same number of mathematical intervals in the horizon or winds which are
distinguished by certain marks and by a lily indicating the north. The bowl
is suspended in the plane of the horizon in æquilibrium in a brass ring
which also is itself suspended transversely in another ring within a box
sufficiently wide with a leaden weight attached; hence it conforms to the
plane of the horizon even though the ship be tossed to and fro by the
waves. The iron works are either a pair with their ends united, or else a
single one of a nearly oval shape with projecting ends, which does its work
more certainly and more quickly. This is to be fitted to the cardboard
circle so that the centre of the circle may be in the middle of the
magnetick iron. But inasmuch as variation arises horizontally from the
point of the meridian which cuts the horizon at right angles, therefore on
account of the variation the makers in different regions and cities mark
out the mariners' compass in different ways, and also attach in different
ways the magnetick needles to the cardboard circle on which are placed the
32 divisions or points. Hence there are commonly in Europe 4 different
constructions and forms. First that of the States on the Mediterranean Sea,
Sicily, Genoa, and the Republick of Venice. In all these the needles are
attached under the rose or lily on the cardboard versorium, so that (where
there is no variation) they are directed to the true north and south
points. Wherefore the north part marked with the lily always shows exactly
the point of variation when the apex itself of the lily on the movable
circle, together with the ends of the magnetick wires attached below, rests
at the point of variation. Yet another is that of Dantzig, and throughout
the Baltic Sea, and the Belgian provinces; {166} in which the iron works
fixed below the circle diverge from the lily ¼ of a rumbe to the east. For
navigation to Russia the divergency is 2/3. But the compasses which are
made at Seville, Lisbon, Rochelle, Bordeaux, Rouen, and throughout all
England have an interval of ½ a rumbe. From those differences most serious
errors have arisen in navigation, and in the marine science. For as soon as
the bearings of maritime places (such as promontories, havens, islands)
have been first found by the aid of the mariners' compass, and the times of
sea-tide or high water determined from the position of the moon over this
or that point (as they say) of the compass, it must be further inquired in
what region or according to the custom of what region that compass was made
by which the bearings of those places and the times of the sea-tides were
first observed and discovered. For one who should use the British compass
and should follow the directions of the marine charts of the Mediterranean
Sea would necessarily wander very much out of the straight course. So also
he that should use the Italian compass in the British, German, or Baltic
Sea, together with marine charts that are made use of in those parts, will
often stray from the right way. These different constructions have been
made on account of the dissimilar variations, so that they might avoid
somewhat serious errors in those parts of the world. But Pedro Nuñez seeks
the meridian by the mariners' compass, or versorium (which the Spanish call
the needle), without taking account of the variation: and he adduces many
geometrical demonstrations which (because of his slight use and experience
in matters magnetical) rest on utterly vicious foundations. In the same
manner Pedro de Medina, since he did not admit variation, has disfigured
his _Arte de Navegar_ with many errors.
* * * * *
CHAP. IX.
Whether the terrestrial longitude can be found from
_the variation_.
Grateful would be this work to seamen, and would bring the greatest advance
to Geography. But B. Porta in chap. 38 of book 7 is mocked by a vain hope
and fruitless opinion. For when he supposes that the magnetick needle would
follow order and proportion in moving along meridians, so that "the neerer
it is to the east, the more it will decline from the Meridian line, toward
the east; and the neerer it comes to the west, the {167} point of the
needle will decline the more to the west" (which is totally untrue), he
thinks that he has discovered a true index of longitude. But he is
mistaken. Nevertheless, admitting and assuming these things (as though they
were perfectly true), he makes a large compass indicating degrees and
minutes, by which these proportional changes of the versorium might be
observed. But those very principles are false, and ill conceived, and very
ill considered; for the versorium does not turn more to the east because a
journey is made toward the east: and although the variation in the more
westerly parts of Europe and the adjoining ocean is to the east and beyond
the Azores is changed a little to the west, yet the variation is, in
various ways, always uncertain, both on account of longitude and of
latitude, and because of the approach toward extensive tracts of land, and
also because of the form of the dominant terrestrial eminences; nor does
it, as we have before demonstrated, follow the rule of any particular
meridian. It is with the same vanity also that Livio Sanuto so greatly
torments himself and his readers. As for the fact that the crowd of
philosophizers and sailors suppose that the meridian passing through the
Azores marks the limits of variation, so that on the other and opposite
side of that meridian a magnetick body necessarily respects the poles
exactly, which is also the opinion of Joannes Baptista Benedictus and of
many other writers on navigation, it is by no means true. Stevinus (on the
authority of Hugo Grotius) in his _Havenfinding Art_ distinguishes the
variation according to the meridians: "It may be seene in the Table of
variations, that in _Coruo_ the Magneticall needle pointeth due North: but
after that, the more a man shal goe towards the East, so much the more also
shall he see the needle varie towards the East [[Greek: anatolizein]], till
he come one mile to the Eastward from _Plimouth_, where the variation
comming to the greatest is 13 degr. 24 min. From hence the Northeasting
[Anatolismus] beginneth to decrease, til you come to _Helmshude_ (which
place is Westward from the North Cape of Finmark) where againe the needle
pointeth due North. Now the longitude from _Coruo_ to _Helmshude_ is 60
degr. Which things being well weighed, it appeareth that the greatest
variation [Chalyboclysis] 13 degr. 24 minutes at _Plimmouth_ (the longitude
whereof is 30 degr.) is in the midst betweene the places where the needle
pointeth due North." But although this is in some part true in these
places, yet it is by no means true that along the whole of the meridian of
the island of Corvo the versorium looks truly to the north; nor on the
meridian of Plymouth is the variation in other places 13 deg. 24 min.--nor
again in other parts of the meridian of Helmshuda does it point to the true
pole. For on the meridian passing through Plymouth in Latitude 60 degrees
the North-easterly variation is greater: in Latitude 40 deg. much less; in
Latitude 20 deg. very small indeed. On the meridian of Corvo, although
there is no variation near the {168} island, yet in Latitude 55 degrees the
variation is about ½ a rumbe to the North-west; in Latitude 20 deg. the
versorium inclines ¼ of a rumbe toward the East. Consequently the limits of
variation are not conveniently determined by means of great circles and
meridians, and much less are the ratios of the increment or decrement
toward any part of the heavens properly investigated by them. Wherefore the
rules of the abatement or augmentation of Northeasting or Northwesting, or
of increasing or decreasing the magnetick deviation, can by no means be
discovered by such an artifice. The rules which follow later for variation
in southern parts of the earth investigated by the same method are
altogether vain and absurd. They were put forth by certain Portuguese
mariners, but they do not agree with the observations, and the observations
themselves are admitted to be bad. But the method of haven-finding in long
and distant voyages by carefully observed variation (such as was invented
by Stevinus, and mentioned by Grotius) is of great moment, if only proper
instruments are in readiness, by which the magnetick deviation can be
ascertained with certainty at sea.
* * * * *
CHAP. X.
Why in various places near the pole the variations
are much more ample than in a
_lower latitude_.
Variations are often slight, and generally null, when the versorium is at
or near the earth's æquator. In a higher Latitude of 60, 70 or 80 deg.
there are not seldom very wide variations. The cause of this is to be
sought partly from the nature of the earth and partly from the disposition
of the versorium. The earth turns magnetick bodies and at the æquator
directs them strongly toward the pole: [227]at the poles there is no
direction, but only a strong coition through the congruent poles. Direction
is therefore weaker near the poles, because by reason of its own natural
tendency to turn, the versorium dips very much, and is not strongly
directed. But since the force of those elevated lands is more vigorous, for
the virtue flows from the whole globe, and since also the causes of
variation are nearer, therefore the versorium deflects the more from its
true direction toward those eminences. It must also be known that the
direction of the versorium on its pin along the plane of the Horizon is
much stronger at the æquator than anywhere else by reason of the
disposition of the {169} versorium; and this direction falls off with an
increase of latitude. For on the æquator the versorium is, following its
natural property, directed along the plane of the horizon; but in other
places it is, contrary to its natural property, compelled into æquilibrium,
and remains there, compelled by some external force: because it would,
according to its natural property, dip below the horizon in proportion to
the latitude, as we shall demonstrate in the book _On Declination_. Hence
the direction falls off and at the pole is itself nothing: and for that
reason a feebler direction is easily vanquished by the stronger causes of
variation, and near the pole the versorium deflects the more from the
meridian. It is demonstrated by means of a terrella: if an iron wire of two
digits length be placed on its æquator, it will be strongly and rapidly
directed toward the poles along the meridian, but more weakly so in the
mid-intervals; while near the poles one may discern a precipitate
variation.
* * * * *
CHAP. XI.
Cardan's error when he seeks the distance of the
_centre of the earth from the centre of the cosmos by the_
motion of the stone of Hercules; in his
_book 5, On Proportions_.
One may very easily fall into mistakes and errors when one is searching
into the hidden causes of things, in the absence of real experiments, and
this is easily apparent from the crass error of Cardan; who deems himself
to have discovered the distances of the centres of the cosmos and of the
earth through a variation of the magnetick iron of 9 degrees. For he
reckoned that everywhere on the earth the point of variation on the Horizon
is always distant nine degrees from the true north, toward the east: and
from thence he forms, by a most foolish error, his demonstrative ratio of
the separate centres.
* * * * *
{170} CHAP. XII.
On the finding of the amount of variation: how great
_is the arc of the Horizon from its arctick or antarctick_
intersection of the meridian, to the point
_respective of the magnetick needle_.
Virtually the true meridian is the chief foundation of the whole matter:
when that is accurately known, it will be easy by a mariners' compass (if
its construction and the mode of attachment of the magnetick iron works are
known) or by some other larger horizontal versorium to exhibit the arc of
variation on the Horizon. By means of a sufficiently large nautical
variation compass (two equal altitudes of the sun being observed before and
after midday), the variation becomes known from the shadow; the altitude of
the sun is observed either by a staff or by a rather large quadrant.
On land the variation is found in another way which is easier, and because
of the larger size of the instrument, more accurate. Let a thick squared
board be made of some suitable wood, the surface of which is two feet in
length and sixteen inches in width: describe upon it some semicircles as in
the following figure, only more in number. In the centre let a brass style
be reared perpendicularly: let there be also a movable pointer reaching
from the centre to the outmost semicircle, and a magnetick versorium in a
cavity covered over with glass: then let the board be exactly adjusted to
the level of the Horizon by the plane instrument with its perpendicular;
and turn the lily of the instrument toward the north, so that the versorium
may rest truly over the middle line of the cavity, which looks toward the
point of variation on on the Horizon. Then at some convenient hour in the
morning (eight or nine for instance) observe the apex of the shadow thrown
by the style when it reaches the nearest semicircle and mark the place of
the apex of this shadow with chalk or ink: then bring round the movable
index to that mark, and observe the degree on the Horizon numbered from the
lily, which the index shows. In the afternoon see when the end of the
shadow shall again reach the periphery of the same semicircle, and,
bringing the index to the apex of the shadow, seek for the degree on the
other side of the lily. From the difference of the degrees becomes known
[Illustration] {172} the variation; the less being taken from the greater,
half the remainder is the arc of variation. The variation is sought by many
other instruments and methods in conjunction with a convenient mariners'
compass; also by a globe, by numbers, and by the ratios of triangles and
sines, when the latitude is known and one observation is made of the sun's
altitude: but those ways and methods are of less use, for it is superfluous
to try to find in winding and roundabout ways what can be more readily and
as accurately found in a shorter one. For the whole art is in the proper
use of the instruments by which the sun's place is expeditiously and
quickly taken (since it does not remain stationary, but moves on): for
either the hand trembles or the sight is dim, or the instrument makes an
error. Besides, to observe the altitude on both sides of the meridian is
just as expeditious as to observe on one side only and at the same time to
find the elevation of the pole. And he who can take one altitude by the
instrument can also take another; but if the one altitude be uncertain,
then all the labour with the globe, numbers, sines and triangles is lost;
nevertheless those exercises of ingenious mathematicians are to be
commended. It is easy for anyone, if he stand on land, to learn the
variation by accurate observations and suitable instruments, especially in
a nearly upright sphere; but on the sea, on account of the motion and the
restlessness of the waters, exact experiments in degrees and minutes cannot
be made: and with the usual instruments scarcely within the third or even
the halt of a rumbe, especially in a higher latitude; hence so many false
and bad records of the observations of navigators. We have, however, taken
care for the finding of the deviation by a sufficiently convenient and
ready instrument, by means of the rising of certain stars, by the rising or
setting of the sun, and in northern regions by the Pole Star: for the
variation is learned with greater certainty even by the skilful with an
instrument which is at once simple and less sensitive to the waves of the
sea. Its construction is as follows.
[228]Let an instrument be made of the form of a true and meridional
mariners' compass of at least one foot in diameter (with a versorium which
is either nude or provided with a cardboard circle): let the limb be
divided into four quadrants, and each quadrant into 90 degrees. The movable
compass-box (as is usual in the nautical instrument) is to be balanced
below by a heavy weight of sixteen pounds. On the margin of the suspended
compass-box, where opposite quadrants begin, let a half-ring rising in an
angular frame in the middle be raised (with the feet of the half-ring fixed
on either side in holes in the margin) so that the top of the frame may be
perpendicular to the plane of the compass; on its top let a rule sixteen
digits in length be fastened at its middle on a joint like a balance beam,
so that it may move, as it were, about a central axis. At the ends of the
rule there are small plates with holes, {173} [Illustration] {174} through
which we can observe the sun or stars. The variation is best observed and
expeditiously by this instrument at the equinoxes by the rising or setting
sun. But even when the sun is in other parts of the zodiack, the deviation
becomes known when we have the altitude of the pole: that being known, one
can learn the amplitude on the Horizon and the distance from the true east
both of the sun and of the following fixed stars by means of a globe, or
tables, or an instrument. Then the variation readily becomes known by
counting from the true east the degrees and minutes of the amplitude at
rising. Observe the preceding star of the three in the Belt of Orion as
soon as it appears on the horizon; direct the instrument toward it and
observe the versorium, for since the star has its rising in the true east
about one degree toward the south, it can be seen how much the versorium is
distant from the meridian, account being taken of that one degree. You will
also be able to observe the arctick pole star when it is on the meridian,
or at its greatest distance from the meridian of about three degrees (the
pole star is distant 2 deg. 55 min. from the pole, according to the
observations of Tycho Brahe), and by the instrument you will learn the
variation (if the star be not on the meridian) by adding or subtracting,
_secundum artem_, the proper reduction [_prostaphæresis_][229] of the
star's distance from the meridian. You will find when the pole star is on
the meridian by knowing the sun's place and the hour of the night: for this
a practised observer will easily perceive without great error by the
visible inclination of the constellation: for we do not take notice of a
few minutes, as do some who, when they toil to track the minutes of degrees
at sea, are in error by a nearly whole rumbe. A practised observer will, in
the rising of sun or stars, allow something for refraction, so that he may
be able to use a more exact calculation.
Bright and conspicuous stars[230] which are
_not far distant from the equator which it
will be useful to observe at their rising and
setting: the amplitude at the Horizon on
rising being known from the altitude of the
pole and from the declination of the stars, by
means of a globe, or tables, or an instrument
whence the variation is perceived by
technical calculation._
{175}
_Right Ascension_ _Declination_
|Oculus Tauri | 62° 55' | 15° 53' N |
|Sinister humerus Orionis | 72° 24' | 4° 5' N |
|Dexter humerus Orionis | 83° 30' | 6° 19' N |
|Præcedens in cingulo Orionis | 77° 46' | 1° 16' S |
|Canis major | 97° 10' | 15° 55' S |
|Canis minor | 109° 41' | 5° 55' N |
|Lucida Hydræ | 137° 10' | 5° 3' S |
|Caput Geminorum australe | 110° 21' | 28° 30' N |
|Caput boreale | 107° 4' | 32° 10' N |
|Cor Leonis | 146° 8' | 13° 47' N |
|Cauda Leonis | 171° 38' | 16° 30' N |
|Spica Virginis | 195° 44' | 8° 34' S |
|Arcturus | 29° 13' | 21° 54' N |
|Cor Aquilæ | 291° 56' | 7° 35' N |
_An instrument for finding the amplitude at rising on the horizon._
Describe the circumference of a circle and let it be divided into quadrants
by two diameters intersecting each other at right angles at its centre. One
of these will represent the æquinoctial circle, the other the axis of the
world. Let each of these quadrants be divided (in the accustomed way) into
90 degrees; on every fifth or tenth of which at each end of each diameter
and on each side let marks (showing the numbers) be inscribed on the two
limbs or margins made for that purpose outside the circumference. Then from
each degree straight lines are drawn parallel to the æquator. You will then
prepare a rule or alhidade equal to the diameter of that circle and divided
throughout into the same parts into which the diameter of the circle
representing the axis of the world is divided. Let there be left a small
appendage attached to the middle of the rule, by which the middle of the
fiducial line itself of the rule may be connected with the centre of the
circle: but to every fifth or tenth part of that rule let numbers be
attached proceeding from the centre toward each side. This circle
represents the plane of the meridian; its centre the actual point of east
or west, _i.e._, the common intersection of the horizon and æquator; all
those lines æquidistant from the æquator denote the parallels of the sun
and stars; the fiducial line of the rule or alhidade represents the
horizon; and its parts signify the degrees of the horizon, beginning from
the point of setting or of rising. {176}
[Illustration]
Therefore if the fiducial line of the rule be applied to the given latitude
of the place reckoned from either end of that diameter which represents the
axis of the world; and if further the given declination of the sun or of
some star from the æquator (less than the complement of the latitude of the
place) be found on the limb of the instrument; then the intersection of the
parallel drawn from that point of the declination with the horizon, or with
the fiducial line of the rule or alhidade, will indicate for the given
latitude of the place the amplitude at rising of the given star or the sun.
* * * * *
{177} CHAP. XIII.
The observations of variation by seamen vary, for the
_most part, and are uncertain: partly from error and inexperience_,
and the imperfections of the instruments; and partly
_from the sea being seldom so calm that the
shadows or lights can remain quite
steady on the instruments_.
After the variation of the compass had first been noticed, some more
diligent navigators took pains to investigate in various ways the
difference of aspect of the mariners' compass. Yet, to the great detriment
of the nautical art, this has not been done so exactly as it ought to have
been. For either being somewhat ignorant they have not understood any
accurate method or they have used bad and absurd instruments, or else they
merely follow some conjecture arising from an ill-formed opinion as to some
prime meridian or magnetick pole; whilst others again transcribe from
others, and parade these observations as their own; and they who, very
unskilful themselves, first of all committed their observations to writing
are, as by the prerogative of time, held in esteem by others, and their
posterity does not think it safe to differ from them. Hence in long
navigations, especially to the East Indies, the records by the Portuguese
of the deviating compass are seen to be unskilful: for whoever reads their
writings will easily understand that they are in error in very many things,
and do not rightly understand the construction of the Portuguese compass
(the lily of which diverges by half a rumbe from the needles toward the
west), nor its use in taking the variation. Hence, while they show the
variation of the compass in different places, it is uncertain whether they
measure the deviation by a true meridional compass or by some other whose
needles are displaced from the lily. The Portuguese (as is patent in their
writings) make use of the Portuguese compass, whose magnetick needles are
fixed aside from the lily by half of one rumbe toward the east. Moreover on
the sea the observation of the variation is a matter of great difficulty,
on account of the motion of the ship and the uncertainty of the deviation,
even with the more skilful observers, if they use the best made instruments
hitherto known and used. Hence there arise different opinions concerning
the magnetick deviation: as, for instance, near the Island of St. Helena
the Portuguese Rodriguez de {178} Lagos measures half a rumbe. The Dutch in
their nautical log fix it at a whole rumbe. Kendall, the expert Englishman,
with a true meridional compass admits only a sixth part of a rumbe. A
little to the East of Cape Agullias Diego Alfonso makes no variation, and
shows by an Astrolabe that the compass remains in the true meridian.
Rodriguez shows that the compass at Cape Agulhas has no variation if it is
of Portuguese construction, in which the needles are inclined half a rumbe
to the East. And there is the same confusion, negligence, and vanity in
very many other instances.
* * * * *
CHAP. XIIII.
On the variation under the æquinoctial line,
_and near it_.
In the North the magnetick needle varies because of the Boreal eminences of
the continent; in the South because of the Austral; at the æquator, if the
regions on both sides were equal, there would be no variation. But because
this rarely happens some variation is often observed under the æquator; and
even at some distance from the æquator of three or 4 degrees toward the
North, there may be a variation arising from the south, if those very wide
and influential southern continents be somewhat near on one side.
* * * * *
CHAP. XV.
The variation of the magnetick needle in the great
Æthiopick and American sea, beyond
_the æquator_.
Discourse hath already been had of the mode and reason of the variation in
the great Atlantick Ocean: but when one has advanced beyond the æquator off
the east coast of Brazil the magnetick needle turns aside toward the
mainland, namely, with that end of it which points to the south; so that
with that end of the versorium it deviates from the true meridian toward
the west; which navigators observe at the other end and suppose a variation
to occur toward the east. But throughout the whole way from the first
promontory on the east of Brazil, by {179} Cape St. Augustine and thence to
Cape Frio, and further still to the mouth of the Strait of Magellan, the
variation is always from the south toward the west with that end of the
versorium which tends toward the antarctick pole. For it is always with the
accordant end that it turns toward a continent. The variation, however,
occurs not only on the coast itself, but at some distance from land, such
as a space of fifty or sixty German miles or even more. But when at length
one has progressed far from land, then the arc begins to diminish: for the
magnetick needle turns aside the less toward what is too far off, and is
turned aside the less from what is present and at hand, since it enjoys
what is present. In the Island of St. Helena (the longitude of which is
less than is commonly marked on charts and globes) the versorium varies by
one degree or nearly two. The Portuguese and others taught by them, who
navigate beyond the Cape of Good Hope to the Indies, set a course toward
the Islands of Tristan d'Acunha, in order that they may enjoy more
favourable winds; in the former part of their course the change of
variation is not great; but after they have approached the islands the
variation increases; and close to the islands it is greater than anywhere
else in the whole course. For the end of the versorium tending to the south
(in which lies the greatest source of the variation) is caught and allured
toward the south-west by the great promontory of the southern land. But
when they proceed onward toward the Cape of Good Hope the variation
diminishes the more they approach it. But on the prime meridian in the
latitude of 45 degrees, the versorium tends to the south-east: and one who
navigates near the coast from Manicongo to the tropick, and a little
beyond, will perceive that the versorium tends from the south to the east,
although not much. At the promontory of Agulhas it preserves slightly the
variation which it showed near the islands of d'Acunha, which nevertheless
is very much diminished because of the greater remoteness from the cause of
variation, and consequently there the southern end of the versorium does
not yet face exactly to the pole.
* * * * *
CHAP. XVI.
On the variation in Nova Zembla.
Variations in parts near the pole are greater (as has been shown before)
and also have sudden changes, as in former years the Dutch explorers
observed not badly, even if those observations were not exact--which indeed
is pardonable in them; for with the usual instruments it is with difficulty
{180} that the truth becomes known in such a high latitude (of about 80
degrees). Now, however, from the deviation of the compass the reason for
there being an open course to the east by the Arctick Ocean appears
manifest; for since the versorium has so ample a variation toward the
north-west, it is demonstrable that a continent does not extend any great
distance in the whole of that course toward the east. Therefore with the
greater hope can the sea be attempted and explored toward the east for a
passage to the Moluccas by the north-east than by the north-west.
* * * * *
CHAP. XVII.
Variation in the Pacifick Ocean.
Passing the Strait of Magellan the deviation on the shore of Peru is toward
the south-east, _i.e._, from the south toward the east. And a similar
deflection would be continued along the whole coast of Peru as far as the
æquator. In a higher latitude up to 45 deg. the variation is greater than
near the æquator; and the deflection toward the south-east is in nearly the
same proportion as was the deviation from the south toward the west on the
eastern shore of South America. From the æquator toward the North there is
little or no variation until one comes to New Galicia; and thence along the
whole shore as far as Quivira the inclination is from the north toward the
east.
* * * * *
CHAP. XVIII.
On the variation in the Mediterranean Sea.
Sicilian and Italian sailors think that in the Sicilian Sea and toward the
east up to the meridian of the Peloponnesus (as Franciscus Maurolycus
relates) the magnetick needle "græcizes," that is, turns from the pole
toward what is called the greek wind or Boreas; that on the shore of the
Peloponnesus it looks toward the true pole; but that when they have
proceeded further east, then it "mistralizes," because it tends from the
pole toward the mistral or north-west wind: which agrees with our rule for
the variation. For as the Mediterranean Sea is extended toward the west
from that meridian, so on the side {181} toward the east the Mediterranean
Sea lies open as far as Palestine; as toward North and East lie open the
whole Archipelago and the neighbouring Black Sea. From the Peloponnesus
toward the north pole the meridian passes through the largest and most
elevated regions of all Europe; through Achaia, Macedonia, Hungary,
Transylvania, Lithuania, Novogardia, Corelia and Biarmia.
* * * * *
CHAP. XIX.
The variation in the interior of large
_Continents_.
Most of the great seas have great variations; in some parts, however, they
have none, but the true directions are toward the pole. On continents,
also, the magnetick needle often deviates from the meridian, as on the edge
of the land and near the borders; but it is generally accustomed to deviate
by a somewhat small arc. In the middle, however, of great regions there are
no variations. Hence in the middle lands of Upper Europe, in the interior
of Asia, and in the heart of Africa, of Peru, and in the regions of North
or Mexican America, the versorium rests in the meridian.
* * * * *
CHAP. XX.
Variation in the Eastern Ocean.
Variation in the Eastern Ocean throughout the whole voyage to Goa and the
Moluccas is observed by the Portuguese; but they err greatly in many
things, following, as they do, the first observers who note down variations
in certain places with ill-adapted instruments, and by no means accurate
observations, or by some conjectures. As, for instance, in Brandöe Island,
they make the versorium deviate by 22 degrees to the north-west. For in no
region or place in the whole world, of not greater latitude, is there so
great a deviation; and, in reality, there the deviation is slight. Also
when they make out that at Mosambique the compass deviates by one rumbe to
the north-west, it is false; even though they use (as they are accustomed
to do) the Portuguese compass: for beyond all doubt on the shore of {182}
Mosambique the versorium inclines ¼ rumbe or even more to the south-west.
Very wrongly also beyond the æquator in the course to Goa they make the
little compass incline by 1½ rumbe to the west: whereas they should rather
have said that in the first part of the course the Portuguese compass
inclines by 1 rumbe: but that the true meridional compass inclines by ½
rumbe only. In order that the amount of variation in the Eastern Ocean may
be accurately settled in most places by our rules, there is needed a more
exact and truer survey of the southern land, which spreads out from the
south to the æquinoctial more than is commonly described on maps and
globes.
* * * * *
CHAP. XXI.
How the deviation of the versorium is augmented and
_diminished by reason of the distance of places_.
In the middle of great and continent lands there is no variation. Nor,
generally, in the middle of very great seas. On the margin of those lands
and seas the variation is often ample, yet not so great as at a little
further distance on the sea. As, for example, near Cape St. Augustine the
compass varies; but at 50 miles from land toward the East it varies more;
and 80 miles off it varies still more; and yet still more at a distance of
100 miles. But from a distance of 100 miles the diminutions of deviation
are slower, when they are navigating toward the mainland, than at a
distance of 80 miles, and at a distance of 80 miles than at 50: for the
deviations change and are diminished rather more swiftly the more they
approach and draw near land than when at a great distance off. As, for
instance, navigating toward Newfoundland the change of variation is more
rapid (that is, it decreases a degree in a smaller arc of the course on the
parallel) when they are not far from land than when they are a hundred
miles distant: but when travelling on land toward the interiors of regions
the changes are slower in the first parts of the journey than when they
come more into the interior.
The ratio of the arcs on a parallel circle, when a versorium is moved
toward continents which extend to the pole, corresponds with the degrees of
variation. Let A be the pole; B the eminences of the dominant lands; at C
there is no variation caused by B, for it is too far away; at D the
variation is very great because the versorium is allured or turned by the
whole earth toward the eminent {183} land B; and moreover it is not
hindered, or restrained or brought back to the pole by the verticity of the
earth; but, tending of its own nature to the pole, it is nevertheless
deflected from it by reason of the site, or position, and convenient
distance of the dominant and high lands.
[Illustration]
Now from C toward D the variation increases; the versorium, however, does
not deviate so rapidly in the first spaces as near D: for more miles are
traversed on the parallel circle C D, near C, in order that the versorium
may deviate by one degree from the pole A, than near D. So also in order
that the variation may be diminished from D toward E more miles are
required near D than near E. Thus the deviations become equal in unequal
courses, whether the variation be increasing or decreasing; and yet the
variation decreases by lesser intervals than it increases. There intervene,
however, many other causes which perturb this proportion.
* * * * *
{184} [Illustration]
BOOK FIFTH.
_CHAP. I._
ON DECLINATION.
In due course we have now come to that notable experiment, and remarkable
motion of magnetick bodies dipping below the horizon by their own rotatory
nature; by the knowledge of which is revealed a unity, a concordancy, and a
mutual agreement between the terrestrial globe and the loadstone (or the
magnetick iron), which is wonderful in itself, and is made manifest by our
teaching. This motion we have made known in many striking experiments, and
have established its rules; and in the following pages we shall demonstrate
the causes of it, in such a way that no sound, logical mind can ever
rightly set at nought or disprove our chief magnetick principles.
Direction, as also variation, is demonstrated in a horizontal plane, when a
balanced magnetick needle comes to rest at some definite point; but
declination is seen to be the motion of a needle, starting from that point
of the horizon, first balanced on its own axis, then excited by a
loadstone, one end or pole of it tending toward the centre of the earth.
And we have found that it takes place in proportion to the latitude of each
region. But that motion arises in truth, not from any motion from the
horizon toward the centre of the earth, but from the turning of the whole
magnetick body toward the whole of the earth, as we shall show hereafter.
Nor does the iron dip from the horizontal in some oblique sphere, according
to the number of degrees of elevation of the pole in the given region, or
by an equal arc in the quadrant, as will appear hereafter. {185}
Instrument of the Declination
[Illustration]
{186} Now how much it dips at every horizon may be ascertained in the first
place by a contrivance, which, however, is not so easily made as is that in
dials for measuring time, in which the needle turns to the points of the
horizon, or in the mariners' compass. From a plank of wood let a smooth and
circular instrument be prepared, at least six digits in diameter, and affix
this to the side of a square pillar, which stands upright on a wooden base.
Divide the periphery of this instrument into 4 quadrants: then each
quadrant into 90 degrees. At the centre of the instrument let there be
placed a brass peg, at the centre of the end of which let there be a small
hollow, well polished. To this wooden instrument let a brass circle or ring
be fixed, about two digits in width, with a thin plate or flat rod of the
same metal, representing the horizon, fixed across it, through the middle
of the circle. In the middle of the horizontal rod let there be another
hollow, which shall be exactly opposite the centre of the instrument, where
the former hollow was made. Afterward let a needle be fashioned out of
steel, as versoria are accustomed to be made. Divide this at right angles
by a thin iron axis (like a cross) through the very middle and centre of
the wire and the cross-piece. Let this dipping-needle be hung (with the
ends of the cross resting in the aforesaid holes) so that it can move
freely and evenly on its axis in the most perfect æquilibrium, so
accurately that it turns away from no one point or degree marked on the
circumference more than from another, but that it can rest quite easily at
any. Let it be fixed upright to the front part of the pillar, whilst at the
edge of the base is a small versorium to show direction. Afterward touch
the iron, suspended by this ingenious method, on both ends with the
opposite ends of a loadstone, according to the scientifick method, but
rather carefully, lest the needle be twisted in any way; for unless you
prepare everything very skilfully and cleverly, you will secure no result.
Then let another brass ring be prepared, a little larger, so as to contain
the former one; and let a glass or a very thin plate of mica be fitted to
one side of it. When this is put over the former ring, the whole space
within remains inclosed, and the versorium is not interfered with by dust
or winds. Dispose the instrument, thus completed, perpendicularly on its
base, and with the small versorium horizontal, in such a way that, while
standing perpendicularly, it may be directed toward the exact magnetical
point respective. Then the end of the needle which looks toward the north
dips below the horizon in northern regions, whilst in southern regions the
end of the needle which looks toward the south tends toward the centre of
the earth, in a certain proportion (to be explained afterward) to the
latitude of the district in question, from the æquator on either side. The
needle, however, must be rubbed on {187} a powerful loadstone; otherwise it
does not dip to the true point, or else it goes past it, and does not
always rest in it. A larger instrument may also be used, whose diameter may
be 10 or 12 digits; but in such an instrument more care is needed to
balance the versorium truly. Care must be taken that the needle be of
steel; also that it be straight; likewise that both ends of the cross-piece
be sharp and fixed at right angles to the needle, and that the cross-piece
pass through the centre of the needle. As in other magnetical motions there
is an exact agreement between the earth and the stone, and a correspondence
manifestly apparent to our senses by means of our experiments; so in this
declination there is a clear and evident concordance of the terrestrial
globe with the loadstone. Of this motion, so important and so long unknown
to all men, the following is the sure and true cause. A magnet-stone is
moved and turned round until one of its poles being impelled toward the
north comes to rest toward a definite point of the horizon. [231]This pole,
which settles toward the north (as appears from the preceding rules and
demonstrations), is the southern, not the boreal; though all before us
deemed it to be the boreal, on account of its turning to that point of the
horizon. A wire or versorium touched on this pole of the stone turns to the
south, and is made into a boreal pole, because it was touched by the
southern terminal of the stone. So if the cusp of a versorium be excited in
a similar manner, it will be directed toward the southern pole of the
earth, and will adjust itself also to it; but the cross (the other end)
will be southern, and will turn to the north of the earth (the earth itself
being the cause of its motion); for so direction is produced from the
disposition of the stone or of the excited iron, and from the verticity of
the earth. But declination takes place when a magnetick is turned round
toward the body of the earth, with its southern end toward the north, at
some latitude away from the æquator. For this is certain and constant, that
exactly under the coelestial æquator, or rather over the æquator of the
terrestrial globe, there is no declination of a loadstone or of iron; but
in whatever way the iron has been excited or rubbed, it settles in the
declination instrument precisely along the plane of the horizon, if it were
properly balanced before. Now this occurs thus because, when the magnetick
body is at an equal distance from either pole, it dips toward neither by
its own versatory nature, but remains evenly directed to the level of the
horizon, as if it were resting on a pin or floating free and unhindered on
water. But when the magnetick substance is at some latitude away from the
æquator, or when either pole of the earth is raised (I do not say raised
above the visible horizon, as the commonly imagined pole of the revolving
universe in the sky, but above the horizon or its centre, or its proper
diameter, æquidistant from the plane of the visible horizon, which is the
true elevation of the terrestrial pole), {188} [Illustration] then
declination is apparent, and the iron inclines toward the body of the earth
in its own meridian. Let A B, for example, be the visible horizon of a
place; C D the horizontal through the earth, dividing it into equal parts;
E F the axis of the earth; G the position of the place. It is manifest that
the boreal pole E is elevated above the point C by as much as G is distant
from the æquator. Wherefore, since at E the magnetick needle stands
perpendicularly in its proper turning (as we have often shown before), so
now at G there is a certain tendency to turn in proportion to the latitude
(the magnetick dipping below the plane of the horizon), and the magnetick
body intersects the horizon at unequal angles, and exhibits a declination
below the horizon. For the same reason, if the declinatory needle be placed
at G, its southern end, the one namely which is directed toward the North,
dips below the plane of the visible horizon A B. And so there is the
greatest difference between a right sphere[232] and a polar or parallel
sphere, in which the pole is at the very Zenith. For in a right sphere the
needle is parallel to the plane of the horizon; but when the coelestial
pole is vertically overhead, or when the pole of the earth is itself the
place of the region, then the needle is perpendicular to the horizon. This
is shown by a round stone. Let a small dipping-needle, of two digits length
(rubbed with a magnet), be hung in the air like a balance, and let the
stone be carefully placed under it; and first let the terrella be at right
angles, as in a right sphere, and as in the first figure; for so the
magnetick needle will remain in equilibrium. But in an oblique position of
the terrella, as in an oblique sphere, and in the second figure, the needle
dips obliquely at one end toward the near pole, but does not rest on the
pole, nor is its dip ruled by the pole, but by the body and mass of the
whole; for the {189} dip in higher latitudes passes beyond the pole. But in
the third position of the terrella the needle is perpendicular; because the
pole of the stone is placed at the top, and the needle tending straight
toward the body reaches to the pole. The cross in the preceding figures
always turns toward the boreal pole of the terrella, having been touched by
the boreal pole of the terrella; the cusp of the needle, having been
touched by the southern pole of the stone, turns to the south. Thus one may
see on a terrella the level, oblique, and perpendicular positions of a
magnetick needle. *
[Illustration]
* * * * *
CHAP. II.
Diagram of declinations of the magnetick needle, when
_excited, in the various portions of the sphere, and horizons_
of the earth, in which there is no variation
_of the declination_.
[Illustration]
{190} As æquator let A B be taken, C the north pole, D the south, E G
dipping-needles in the northern, H F in the southern part of the earth or
of a terrella. In the diagram before us all the cusps have been touched by
the true Arctick pole of the terrella.
Here we have the level position of the magnetick needle on the æquator of
the earth and the stone, at A and B, and its perpendicular position at C,
D, the poles; whilst at the places midway between, at a distance of 45
degrees, the crosses of the needle dip toward the south, but the cusps just
as much toward the north. Of which thing the reason will become clear from
the demonstrations that follow.
_* Diagram of the rotation and declination of a terrella_
conforming to the globe of the earth, for a
_latitude of 50 degrees north._
[Illustration]
A is the boreal pole of the earth or of a rather large terrella, B the
southern, C a smaller terrella, E the southern pole of the smaller
terrella, dipping in the northern regions[233]. The centre C is placed on
the surface of the larger terrella, because the smaller terrella shows some
variation on account of the length of the axis; inappreciable, however, on
the earth. Just as a magnetick needle dips in a regional latitude of 50
degrees, so also the axis of a stone (of a spherical stone, of course) is
depressed below the horizon, and its natural austral pole falls, and its
boreal pole is raised on the {191} south toward the Zenith. In the same way
also a circular disc of iron behaves, which has been carefully touched at
opposite parts on its circumference; but the magnetical experiments are
less clear on account of the feebler forces in round pieces of iron.
_Variety in the declinations of iron spikes at various latitudes of a
terrella._
[Illustration]
The declination of a magnetick needle above a terrella is shown by means of
several equal iron wires, of the length of a barleycorn, arranged along a
meridian. The wires on the æquator are directed by the virtue of the stone
toward the poles, and lie down upon its body along the plane of its
horizon. The nearer they are brought to the poles, the more they are raised
up by their versatory nature. At the poles themselves they point
perpendicularly toward the very centre. But iron spikes, if they are of
more than a due length, are not raised straight up except on a vigorous
stone.
* * * * *
CHAP. III.
*
An indicatory instrument, showing by the virtue of a
_stone the degrees of declination from the horizon_
of each several latitude.
{192} [Illustration] {193} _Description of the Instrument, and its use._
Take a terrella of the best strong loadstone, and homogeneous throughout,
not weakened by decay or by a flaw in any parts; let it be of a fair size,
so that its diameter is six or seven digits; and let it be made exactly
spherical. Having found its poles according to the method already shown,
mark them with an iron tool; then mark also the æquinoctial circle.
Afterwards in a thick squared block of wood, one foot in size, make a
hemispherical hollow, which shall hold half of the terrella, and such that
exactly one half of the stone shall project above the face of the block.
Divide the limb close to this cavity (a circle having been drawn round it
for a meridian) into 4 quadrants, and each of these into 90 degrees. Let
the terminus of the quadrants on the limb be near the centre of a quadrant
described on the block, also divided into 90 degrees. At that centre let a
short, slender versorium (its other end being rather sharp and elongated
like a pointer) be placed in æquilibrio on a suitable pin. It is manifest
that when the poles of the stone are at the starting points of the
quadrants, then the versorium lies straight, as if in æquilibrio, over the
terrella. But if you move the terrella, so that the pole on the left hand
rises, then the versorium rises on the meridian in proportion to the
latitude, and turns itself as a magnetick body; and on the quadrant
described on the flat surface of the wood, the degree of its turning or of
the declination is shown by the versorium. The rim of the cavity represents
a meridional circle, to which corresponds some meridian circle of the
terrella, since the poles on both sides are within the circumference of the
rim itself. These things clearly always happen on the same plan on the
earth itself when there is no variation; but when there is variation,
either in the direction or in the declination (a disturbance, as it were,
in the true turning, on account of causes to be explained later), then
there is some difference. Let the quadrant be near the limb, or have its
centre on the limb itself, and let the versorium be very short, so as not
to touch the terrella, because with a versorium that is longer or more
remote, there is some error; for it has a motion truly proportionate to the
terrella only on the surface of the terrella. But if the quadrant, being
far distant from the terrella, were moved within the orbe of virtue of the
terrella toward the pole on some circle concentrick with the terrella, then
the versorium would indicate the degrees of declination on the quadrant, in
proportion to and symmetrically with that circle, not with the terrella.
* * * * *
{194} CHAP. IIII.
Concerning the length of a versorium convenient
_for declination on a terrella_.
Declination being investigated on the earth itself by means of a
declination instrument, we may use either a short or a very long versorium,
if only the magnetick virtue of the stone that touches it is able to
permeate through the whole of its middle and through all its length. For
the greatest length of a versorium has no moment or perceptible proportion
to the earth's semi-diameter. On a terrella, however, or in a plane near a
meridian of a terrella, a short versorium is desirable, of the length, say,
of a barleycorn; for longer ones (because they reach further) dip and turn
toward the body of the terrella suddenly and irregularly in the first
degrees of declination. [Illustration] For example, as soon as the long
versorium is moved forward from the aequator A to C, it catches on the
stone with its cusp (as if with a long extended wing), when the cusp
reaches to the parts about B, which produce a greater rotation than at C.
And the extremities of longer wires also and rods turn irregularly, just as
iron wires and balls of iron and other orbicular loadstones are likewise
turned about irregularly by a long non-orbicular loadstone. Just so
magneticks or iron bodies on the surface of a terrella ought not to have
too long an axis, but a very short one; so that they may make a declination
on the terrella truly and naturally proportionate to that on the earth. A
long versorium also close to a terrella with difficulty stands steady in a
horizontal direction on a right sphere, and, beginning to waver, it dips
immediately to one side, especially the end that was touched, or (if both
were touched) the one which felt the stone last.
* * * * *
{195} CHAP. V.
That declination does not arise from the attraction
of the loadstone, but from a disposing and
_rotating influence_.
In the universe of nature that marvellous provision of its Maker should be
noticed, whereby the principal bodies are restrained within certain
habitations and fenced in, as it were (nature controlling them). For this
reason the stars, though they move and advance, are not thrown into
confusion. Magnetical rotations also arise from a disposing influence,
whether in greater and dominating quantity, or in a smaller, and compliant
quantity, even though it be very small. For the work is not accomplished by
attraction, but by an incitation of each substance, by a motion of
agreement toward fixed bounds, beyond which no advance is made. For if the
versorium dipped by reason of an attractive force, then a terrella made
from a very strong magnetick stone would cause the versorium to turn toward
itself more than one made out of an average stone, and a piece of iron
touched with a vigorous loadstone would dip more. This, however, never
happens. Moreover, an iron snout placed on a meridian in any latitude does
not raise a spike more toward the perpendicular than the stone itself,
alone and unarmed; although when thus equipped, it plucks up and raises
many greater weights[234]. But if a loadstone be sharper toward one pole,
toward the other blunter, the sharp end or pole allures a magnetick needle
more strongly, the blunt, thick end makes it rotate more strongly; but an
orbicular stone * makes it rotate strongly and truly, in accordance with
magnetick rules and its globular form. A long stone, on the other hand,
extended from pole to pole, moves a versorium toward it irregularly; for in
this case the pole of the versorium always looks down on the pole itself.
Similarly also, if the loadstone have been made in the shape of a circle,
and its poles are on the circumference, whilst the body of it is plane, not
globular, if the plane be brought near a versorium, the versorium does not
move with the regular magnetick rotation, as on a terrella; but it turns
looking always toward the pole of the loadstone, which has its seat on the
circumference of the plane. Moreover, if the stone caused the versorium to
rotate by attracting it, then in the first degrees of latitude, it would
attract the end of a short versorium toward the body itself of the
terrella; yet it does not so attract it that they are brought into contact
and unite; but the versorium rotates just so far as nature demands, as is
clear from this example. {196} [Illustration] * For the cusp of a versorium
placed in a low latitude does not touch the stone or unite with it, but
only inclines toward it. Moreover, when a magnetick body rotates in
dipping, the pole of the versorium is not stayed or detained by the pole of
the earth or terrella; but it rotates regularly, and does not stop at any
point or bound, nor point straight to the pole toward which the centre of
the versorium is advancing, unless on the pole itself, and once only
between the pole and the æquator; but it dips as it advances, according as
the change of position of its centre gives a reason for its inclination in
accordance with rules magnetical. The declination of a magnetick needle in
water also, as demonstrated in the following pages, is a fixed
quantity[235]; the magnetick needle does not descend to the bottom of the
vessel, but remains steady in the middle, rotated on its centre according
to its due amount of declination. This would not happen, if the earth or
its poles by their attraction drew down the end of the magnetick needle, so
that it dipped in this way.
* * * * *
CHAP. VI.
On the proportion of declination to latitude[236], and
_the cause of it_.
Concerning the making of an instrument for finding declination, the causes
and manner of declination, and the different degrees of rotation in
different places, the inclination of the stone, and concerning an
instrument indicating by the influence of a stone the degree of declination
from any horizon we have already spoken. Then we spoke about needles on the
meridian of a stone, and their rotation shown for various latitudes by
their rise toward the perpendicular. We must now, however, treat more fully
of the causes of the degree of that inclination. Whilst a loadstone and a
magnetick iron wire are moved along a meridian from the aequator toward the
pole, they rotate toward a round loadstone, as also toward the earth with a
circular movement. On a right horizon (just as also on the æquinoctial of
{197} the stone) the axis of the iron, which is its centre line, is a line
parallel to the axis of the earth. When that axis reaches the pole, which
is the centre of the axis, it stands in the same straight line with the
axis of the earth. The same end of the iron which at the æquator looks
south turns to the north. For it is not a motion of centre to centre, but a
natural turning of a magnetick body to a magnetick body, and of the axis of
the body to the axis; it is not in consequence of the attraction of the
pole itself that the iron points to the earth's polar point. Under the
æquator the magnetick needle remains in æquilibrio horizontally; but toward
the pole on either side, in every latitude from the beginning of the first
degree right up to the ninetieth, it dips. The magnetick needle does not,
however, in proportion to any number of degrees or any arc of latitude fall
below the horizon just that number of degrees or a similar arc, but a very
different one: because this motion is not really a motion of declination,
but is in [Illustration] reality a motion of rotation, and it observes an
arc of rotation according to the arc of latitude. Therefore a magnetick
body A, while it is advancing over the earth itself, or a little earth or
terrella, from the æquinoctial G toward the pole B, rotates on its own
centre, and halfway on the progress of its centre[237] from the æquator to
the pole B it is pointing toward the æquator at F, midway between the two
poles. Much more quickly, therefore, must the versorium rotate than its
centre advances, in order that by rotating it may face straight toward the
point F. Wherefore the motion of this rotation is rapid in the first
degrees from the æquator, namely, from A to L; but more tardy in the later
degrees from L to B, when facing from the æquator at F to C. But if the
declination were equal to the latitude (_i.e._, always just as many degrees
from the horizon, as the centre of the versorium has receded from the
æquator), then the magnetick needle would be following some potency and
peculiar virtue of the centre, as if it {198} were a point operating by
itself. But it pays regard to the whole, both its mass, and its outer
limits; the forces of both uniting, as well of the magnetick versorium as
of the earth. *
* * * * *
CHAP. VII.
Explanation of the diagram of the rotation of
_a magnetick needle_.
[Illustration]
Suppose A C D L to be the body of the earth or of a terrella, its centre M,
Æquator A D, Axis C L, A B the Horizon, which changes according to the
place. From the point F on a Horizon distant from the æquator A by the
length of C M, the semi-diameter of the earth or terrella, an arc is
described to H as the limit of the quadrants of declination; for {199} all
the quadrants of declination serving the parts from A to C begin from that
arc, and terminate at M, the centre of the earth. The semi-diameter of this
arc is a chord drawn from the æquator A to the pole C; and a line produced
along the horizon from A to B, equal to that chord, gives the beginning of
the arc of the limits of arcs of rotation and revolution, which is
continued as far as G. For just as a quadrant of a circle about the centre
of the earth (whose beginning is on the horizon, at a distance from the
æquator equal to the earth's semi-diameter) is the limit of all quadrants
of declination drawn from each several horizon to the centre; so a circle
about the centre from B, the beginning of the first arc of rotation, to G
is the limit of the arcs of rotation. The arcs of rotation and revolution
of the magnetick needle are intermediate between the arcs of rotation B L
and G L. The centre of the arc is the region itself or place in which the
observation is being made; the beginning of the arc is taken from the
circle which is the limit of rotations, and it stops at the opposite pole;
as, for example, from O to L, in a latitude of 45 degrees. Let any arc of
rotation be divided into 90 equal parts from the limit of the arcs of
rotation toward the pole; for whatever is the degree of latitude of the
place, the part of the arc of rotation which the magnetick pole on or near
the terrella or the earth faces in its rotation is to be numbered similarly
to this. The straight lines in the following larger diagram show this. The
magnetick rotation at the middle point in a latitude of 45 degrees is
directed toward the æquator, in which case also that arc is a quadrant of a
circle from the limit to the pole; but previous to this all the arcs of
rotation are greater than a quadrant, whilst after it they are smaller; in
the former the needle rotates more quickly, but in the succeeding positions
gradually more slowly. For each several region there is a special arc of
rotation, in which the limit to which the needle rotates is according to
the number of degrees of latitude of the place in question; so that a
straight line drawn from the place to the point on that arc marked with the
number of degrees of latitude shows the magnetick direction, and indicates
the degree of declination at the intersection of the quadrant of
declination which serves the given place. Take away the arc of the quadrant
of declination drawn from the centre to the line of direction; that which
is left is the arc of declination below the horizon. As, for example, in
the rotation of the versorium N, whose line respective proceeds to D, from
the quadrant of declination, S M, take away its arc R M; that which is left
is the arc of declination: how much, that is, the needle dips in the
latitude of 45 degrees.
* * * * *
{200} CHAP. VIII.
Diagram of the rotation of a magnetick needle,
_indicating magnetical declination in all latitudes, and_
from the rotation and declination, the
_latitude itself_.
In the more elaborate diagram a circle of rotations and a circle of
declinations are adjusted to the body of the earth or terrella, with a
first, a last, and a middle arc of rotation and declination. Now from each
fifth division of the arc which limits all the arcs of rotation (and which
are understood[238] as divided into 90 equal parts) arcs are drawn to the
pole, and from every fifth degree of the arc limiting the quadrants of
declination, quadrants are drawn to the centre; and at the same time a
spiral line is drawn, indicating (by the help of a movable quadrant) the
declination in every latitude. Straight lines showing the direction of the
needle are drawn from those degrees which are marked on the meridian of the
earth or a terrella to their proper arcs and the corresponding points on
those arcs.
To ascertain the elevation of the pole or the latitude of a place
anywhere
_in the world, by means of the following diagram, turned into
a magnetick instrument, without the help of the coelestial
bodies, sun, planets, or fixed stars, in fog
and darkness_.
[Illustration]
We may see how far from unproductive magnetick philosophy is, how
agreeable, how helpful, how divine! Sailors when tossed about on the waves
with continuous cloudy weather, and unable by means of the coelestial
luminaries to learn anything about the place or the region in which they
are, with a very slight effort and with a small instrument are comforted,
and learn the latitude of the place. With a declination instrument the
degree of declination of the magnetick needle below the horizon is
observed; that degree is noted on the inner arc of the quadrant, and the
quadrant is turned round about the centre of the instrument until that
degree on the quadrant touches the spiral line; then in the open space B at
the centre of the quadrant the latitude of the region on {201} the
circumference of the globe is discerned by means of the fiducial line A B.
Let the diagram be fixed on a suitable flat board, and let the centre of
the corner A of the quadrant be fastened to the centre of it, so that the
quadrant may rotate on that centre. But it must be understood that there is
also in certain places a variation in the declination on account of causes
already mentioned (though not a large one), which it will be an assistance
also to allow for on a likely estimate; and it will be especially helpful
to observe this variation in various places, as it seems to present greater
difficulty than the variation in direction; but it is easily learnt with a
declination instrument, when it dips more or less than the line in the
diagram.
[Illustration]
_To observe magnetick declination at sea_.
Set upon our variation instrument a declination instrument; a wooden disc
being placed between the round movable {202} compass and the declination
instrument: but first remove the versorium, lest the versorium should
interfere with the dipping needle. In this way (though the sea be rough)
the compass box will remain upright at the level of the horizon. The stand
of the declination instrument must be directed by means of the small
versorium at its base, which is set to the point respective of the
variation, on the great circle of which (commonly called the magnetick
meridian), the plane of the upright box is arranged; thus the declinatorium
(by its versatory nature) indicates the degree of declination.
In a declination instrument the magnetick needle, which
_in a meridional position dips, if turned
along a parallel hangs perpendicularly._
In a proper position a magnetick needle, while by its rotatory nature
conformed to the earth, dips to some certain degree below the horizon on an
oblique sphere. But when the plane of the instrument is moved out of the
plane of the meridian, the magnetick needle (which tends toward the pole)
no longer remains at the degree of its own declination, but inclines more
toward the centre; for the force of direction is stronger than that of
declination, and all power of declination is taken away, if the plane of
the instrument is on a parallel. For then the magnetick needle, because it
cannot maintain its due position on account of the axis being placed
transversely, faces down perpendicularly to the earth; and it remains only
on its own meridian, or on that which is commonly called the magnetick
meridian.
* * * * *
CHAP. IX.
Demonstration of direction, or of variation from the
_true direction, at the same time with declination, by_
means of only a single motion in water, due
_to the disposing and rotating virtue._
[Illustration]
Fix a slender iron wire of three digits length through * a round cork, so
that the cork may support the iron in water. Let this water be in a
good-sized glass vase or bowl. Pare the round cork little by little with a
very sharp knife (so that it may remain round), until it will stay
motionless one or two digits below the face of the water; and let the wire
be evenly balanced. {203} [239]Rub one end of the wire thus prepared on the
boreal end of a loadstone and the other on the southern part of the stone
(very skilfully, so that the cork may not be moved ever so little from its
place) and again place it in the water; then the wire will dip with a
circular motion on its own centre below the plane of the horizon, in
proportion to the latitude of the region; and, even while dipping, will
also show the point of variation (the true direction being perturbed). Let
the loadstone (that with which the iron is rubbed) be a strong one, such as
is needed in all experiments on magnetick declination. When the iron, thus
put into the water and prepared by means of the loadstone, has settled in
the dip, the lower end remains at the point of variation on the arc of a
great circle or magnetick meridian passing through the Zenith or vertex,
and the point of variation on the horizon, and the lowest point of the
heavens, which they call the Nadir. This fact is shown by placing a rather
long magnetick versorium on one side a little way from the vase. This is a
demonstration of a more absolute conformity of a magnetick body with the
earth's body as regards unity; in it is made {204} apparent, in a natural
manner, the direction, with its variation, and the declination. But it must
be understood that as it is a curious and difficult experiment, so it does
not remain long in the middle of the water, but sinks at length to the
bottom, when the cork has imbibed too much moisture.
* * * * *
CHAP. X.
On the variation of the declination.
Direction has been spoken of previously, and also * variation, which is
like a kind of dragging aside of the direction. Now in declination such
irregular motion is also noticed, when the needle dips beyond the proper
point or when sometimes it does not reach its mark. There is therefore a
variation of declination, being the arc of a magnetick meridian between the
true and apparent declination. For as, on account of terrestrial
elevations, magnetick bodies are drawn away from the true meridian, so also
the needle dips (its rotation being increased a little) beyond its genuine
position. For as variation is a deviation of the direction, so also, owing
to the same cause, there is some error of declination, though often very
slight. Sometimes, also, when there is no variation of direction in the
horizontal, there may nevertheless be variation of the declination; namely,
either when more vigorous parts of the earth crop out exactly meridionally,
_i.e._ under the very meridian; or when those parts are less powerful than
nature in general requires; or when the virtue is too much intensified in
one part, or weakened in another, just as one may observe in the vast
ocean. And this discrepant nature and varying effect may be easily seen in
certain parts of almost any round loadstone. Inæquality of power is
recognized in any part of a terrella by trial of the demonstration in chap.
2 of this book. But the effect is clearly demonstrated by the instrument
for showing declination in chap. 3 of this book.
* * * * *
{205} CHAP. XI.
On the essential magnetick activity sphærically
_effused._
Discourse hath often been held concerning the * poles of the earth and of
the stone, and concerning the æquinoctial zone; whilst lately we have been
speaking about the declining of magneticks toward the earth and toward the
terrella, and the causes of it. But while by various and complicated
devices we have laboured long and hard to arrive at the cause of this
declination, we have by good fortune found out a new and admirable (beyond
the marvels of all virtues magnetical) science of the orbes themselves. For
such is the power of magnetick globes, that it is diffused and extended
into orbes outside the body itself, the form being carried beyond the
limits of the corporeal substance; and a mind diligently versed in this
study of nature will find the definite causes of the motions and
revolutions. The same powers of a terrella exist also within the whole orbe
of its power; and these orbes at any distance from the body of the terrella
have in themselves, in proportion to their diameter and the magnitude of
their circumference, their own limits of influences, or points wherein
magnetick bodies rotate; but they do not look toward the same part of the
terrella or the same point at any distance from the same (unless they be on
the axis of the orbes and of the terrella); but they always tend to those
points of their own orbes, which are distant by similar arcs from the
common axis of the orbes. As, for example, in the following diagram, we
show the body of a terrella, with its poles and æquator; and also a
versorium on three other concentrick orbes around the terrella at some
distance from it. In these orbes (as in all those which we may imagine
without end) the magnetick body or versorium conforms to its own orbe in
which it is located, and to its diameter and poles and æquator, not to
those of the terrella; and it is by them and according to the magnitude of
their orbes that the magnetick body is governed, rotated, and directed, in
any arc of that orbe, both while the centre of the magnetick body stands
still, and also while it moves along. And yet we do not mean that the
magnetick forms and orbes exist in air or water or in any medium that is
not magnetical; as if the air or the water were susceptible of them, or
were induced by them; for the forms are only effused and really subsist
when magnetick substances are there; whence a magnetick body is laid hold
of within the forces and limits of the orbes; and within the orbes
magneticks {206} dispose magneticks and incite them, as if the orbes of
virtue were solid and material loadstones. For the magnetick force does not
pass through the whole medium or really exist as in a continuous body; so
the orbes are magnetick, and yet not real orbes nor existent by themselves.
_Diagram of motions in magnetick orbes._
[Illustration]
A B is the axis of the terrella and of the orbes, C D the æquator. On all
the orbes, as on the terrella, at the equator the versorium arranges itself
along the plane of the horizon; on the axis it everywhere looks
perpendicularly toward the centre; in the intermediate spaces E looks
toward D; and G looks toward H, not toward F, as the versorium L does on
the surface of the terrella. But as is the relation of L to F on the
surface of the terella, so is that of G to H on its orbe and of E to D on
its orbe; also all the rotations on {207} the orbes toward the termini of
the orbes are such as they are on the surface of the terrella, or toward
the termini of its surface. But if in the more remote orbes this fails
somewhat at times, it happens on account of the sluggishness of the stone,
or on account of the feebler forces due to the too great distance of the
orbes from the terrella.
_Demonstration._
Set upon the instrumental diagram described farther back [chap. 3] a plate
or stiff circle of brass or tin, on which may be described the magnetick
orbes, as in the diagram above; and in the middle let a hole be made
according to the size of the terrella, so that the plate may lie evenly on
the wood about the middle of the terrella on a meridional circle. Then let
a small versorium of the length of a barley-corn be placed on any orbe;
upon which, when it is moved to various positions on the same circle, it
will always pay regard to the dimensions of that orbe, not to those of the
stone; as is shown in the diagram of the effused magnetick forms.
While some assign occult and hidden virtues of substances, others a
property of matter, as the causes of the wonderful magnetical effects; we
have discovered the primary substantive form of globes, not from a
conjectural shadow of the truth of reasons variously controverted; but we
have laid hold of the true efficient cause, as from many other
demonstrations, so also from this most certain diagram of magnetick forces
effused by the form. Though this (the form) has not been brought under any
of our senses, and on that account is the less perceived by the intellect,
it now appears manifest and conspicuous even to the eyes through this
essential activity which proceeds from it as light from a lamp. And here it
must be noted that a magnetick needle, moved on the top of the earth or of
a terrella or of the effused orbes, makes two complete rotations in one
circuit of its centre, like some epicycle about its orbit.
* * * * *
{208} CHAP. XII.
Magnetick force is animate, or imitates life; and in
many things surpasses human life, while this is bound
_up in the organick body_.
A loadstone is a wonderful thing in very many experiments, and like a
living creature. And one of its remarkable virtues is that which the
ancients considered to be a living soul in the sky, in the globes and in
the stars, in the sun and in the moon. For they suspected that such various
motions could not arise without a divine and animate nature, immense bodies
turned about in fixed times, and wonderful powers infused into other
bodies; whereby the whole universe flourishes in most beautiful variety,
through this primary form of the globes themselves. The ancients, as
Thales, Heraclitus, Anaxagoras, Archelaus, Pythagoras, Empedocles,
Parmenides, Plato, and all the Platonists, and not only the older Greeks,
but the Egyptians and Chaldæans, seek for some universal life in the
universe, and affirm that the whole universe is endowed with life.
Aristotle affirms that not the whole universe is animate, but only the sky;
but he maintains that its elements are inanimate; whilst the stars
themselves are animate. We, however, find this life in globes only and in
their homogenic parts; and though it is not the same in all globes (for it
is much more eminent in the sun and in certain stars than in others of less
nobility) yet in very many the lives of the globes agree in their powers.
For each several homogenic part draws to its own globe in a similar manner,
and has an inclination to the common direction of the whole in the
universe; and the effused forms extend outward in all, and are carried out
into an orbe, and have bounds of their own; hence the order and regularity
of the motions and rotations of all the planets, and their courses, not
wandering away, but fixed and determined. Wherefore Aristotle concedes life
to the sphæres themselves and to the orbes of the heavens (which he
feigns), because they are suitable and fitted for a circular motion and
actions, and are carried along in fixed and definite courses. It is surely
wonderful, why the globe of the earth alone with its emanations is
condemned by him and his followers and cast into exile (as senseless and
lifeless), and driven out of all the perfection of the excellent universe.
It is treated as a small corpuscle in comparison with the whole, and in the
numerous concourse of many thousands it is obscure, disregarded, and
unhonoured. {209} With it also they connect the kindred elements, in a like
unhappiness, wretched and neglected. Let this therefore be looked upon as a
monstrosity in the Aristotelian universe, in which everything is perfect,
vigorous, animated; whilst the earth alone, an unhappy portion, is paltry,
imperfect, dead, inanimate, and decadent. But on the other hand Hermes,
Zoroaster, Orpheus, recognize a universal life. We, however, consider that
the whole universe is animated, and that all the globes, all the stars, and
also the noble earth have been governed since the beginning by their own
appointed souls and have the motives of self-conservation. Nor are there
wanting, either implanted in their homogenic nature or scattered through
their homogenic substance, organs suitable for organic activity, although
these are not fashioned of flesh and blood as animals, or composed of
regular limbs, which are also hardly perceptible in certain plants and
vegetables; since regular limbs are not necessary for all life. Nor can any
organs be discerned or imagined by us in any of the stars, the sun, or the
planets, which are specially operative in the universe; yet they live and
imbue with life the small particles in the prominences on the earth. If
there be anything of which men can boast, it is in fact life, intelligence;
for the other animals are ennobled by life; God also (by whose nod all
things are ruled) is a living soul. Who therefore will demand organs for
the divine intelligences, which rise superior to every combination of
organs and are not restrained by materialized organs? But in the several
bodies of the stars the implanted force acts otherwise than in those divine
existences which are supernaturally ordained; and in the stars, the sources
of things, otherwise than in animals; in animals again otherwise than in
plants. Miserable were the condition of the stars, abject the lot of the
earth, if that wonderful dignity of life be denied to them, which is
conceded to worms, ants, moths, plants, and toadstools; for thus worms,
moths, grubs would be bodies more honoured and perfect in nature; for
without life no body is excellent, valuable, or distinguished. But since
living bodies arise and receive life from the earth and the sun, and grass
grows on the earth apart from any seeds thrown down (as when soil is dug up
from deep down in the earth, and put on some very high place or on a very
high tower, in a sunny spot, not so long after various grasses spring up
unbidden) it is not likely that they can produce what is not in them; but
they awaken life, and therefore they are living. Therefore the bodies of
the globes, as important parts of the universe, in order that they might be
independent and that they might continue in that condition, had a need for
souls to be united with them, without which there can be neither life, nor
primary activity, nor motion, nor coalition, nor controlling power, nor
harmony, nor endeavour, nor sympathy; and without which there would be no
generation {210} of anything, no alternations of the seasons, no
propagation; but all things would be carried this way and that, and the
whole universe would fall into wretchedest Chaos, the earth in short would
be vacant, dead, and useless. But it is only on the superficies of the
globes that the concourse of living and animated beings is clearly
perceived, in the great and pleasing variety of which the great
master-workman is well pleased. But those souls which are restrained within
a kind of barrier and in prison cells, as it were, do not emit immaterial
effused forms outside the limits of their bodies; and bodies are not moved
by them without labour and waste. They are brought and carried away by a
breath; and when this has calmed down or been suppressed by some untoward
influence, their bodies lie like the dregs of the universe and as the
refuse of the globes. But the globes themselves remain and continue from
year to year, move, and advance, and complete their courses, without waste
or weariness. The human soul uses reason, sees many things, inquires about
many more; but even the best instructed receives by his external senses (as
through a lattice) light and the beginnings of knowledge. Hence come so
many errors and follies, by which our judgments and the actions of our
lives are perverted; so that few or none order their actions rightly and
justly. But the magnetick force of the earth and the formate life or living
form of the globes, without perception, without error, without injury from
ills and diseases, so present with us, has an implanted activity, vigorous
through the whole material mass, fixed, constant, directive, executive,
governing, consentient; by which the generation and death of all things are
carried on upon the surface. For, without that motion, by which the daily
revolution is performed, all earthly things around us would ever remain
savage and neglected, and more than deserted and absolutely idle. But those
motions in the sources of nature are not caused by thinking, by petty
syllogisms, and theories, as human actions, which are wavering, imperfect,
and undecided; but along with them reason, instruction, knowledge,
discrimination have their origin, from which definite and determined
actions arise, from the very foundations that have been laid and the very
beginnings of the universe; which we, on account of the infirmity of our
minds, cannot comprehend. Wherefore Thales, not without cause (as Aristotle
relates in his book _De Anima_), held that the loadstone was animate, being
a part and a choice offspring of its animate mother the earth.
* * * * *
{211} [Illustration]
BOOK SIXTH.
_CHAP. I._
ON THE GLOBE OF THE EARTH, THE
_great magnet_.
Hitherto our subject hath been the loadstone and things magnetical: how
they conspire together, and are acted upon, how they conform themselves to
the terrella and to the earth. Now must we consider separately the globe
itself of the earth. Those experiments which have been proved by means of
the terrella, how magnetick things conform themselves to the terrella, are
all or at least the principal and most important of them, displayed by
means of the earth's Body: And to the earth things magnetical are in all
respects associate. First, as in the terrella the æquator, meridians,
parallels, axis, poles are natural boundaries, as numerous experiments make
plain: So also in the earth these boundaries are natural, not mathematical
only (as all before us used to suppose). These boundaries the same
experiments display and establish in both cases alike, in the earth no less
than in the terrella. Just as on the periphery of a terrella a loadstone or
a magnetick piece of iron is directed to its proper pole: so on the earth's
surface are there turnings-about, peculiar, manifest, and constant on
either side of the æquator. Iron is indued with verticity by being extended
toward a pole of the earth, just as toward a pole of the terrella: By its
being placed down also, and cooling toward the earth's pole after the
pristine verticity has {212} been annulled by fire, it acquires new
verticity, conformable to its position earthward. Iron rods also, when
placed some considerable time toward the poles, acquire verticity merely by
regarding the earth; just as the same rods, if placed toward the pole of a
loadstone, even without touching it, receive polar virtue. There is no
magnetick body that in any way runs to the terrella which does not also
wait upon the earth. As a loadstone is stronger at one end on one side or
other[240] of its æquator: so is the same property displayed by a small
terrella upon the surface of a larger terrella. According to the variety
and artistick skill in the rubbing of the magnetick iron upon the terrella,
so do the magnetick things perform their function more efficiently or more
feebly. In motions toward the earth's body, as toward the terrella a
variation is displayed due to the unlikeness, inequality, and imperfection
of its eminences: So every variation of the versorium or mariners' compass,
everywhere by land or by sea, which thing has so sorely disturbed men's
minds, is discerned and recognized as due to the same causes. The magnetick
dip (which is the wonderful turning of magnetick things to the body of the
terrella) in systematick course, is seen in clearer light to be the same
thing upon the earth. And that single experiment, by a wonderful
indication, as with a finger, proclaims the grand magnetick nature of the
earth to be innate and diffused through all her inward parts. A magnetick
vigour exists then in the earth just as in the terrella, which is a part of
the earth, homogenic in nature with it, but rounded by Art, so as to
correspond with the earth's globous shape and in order that in the chief
experiments it might accord with the globe of the earth.
* * * * *
CHAP. II.
The Magnetick axis of the Earth
_persists invariable_.
As in the very first beginnings of the moving world, the earth's magnetick
axis passed through the midst of the earth: so now it tends through the
centre to the same points of the superficies; the circle and plane of the
æquinoctial line also persisting. For not without the vastest overthrow of
the terrene mass can these natural boundaries be changed, as it is easy to
gather from magnetick demonstrations. Wherfore the opinion of Dominicus
Maria of Ferrara, a most talented man, who was the teacher of Nicolas
Copernicus, must be cancelled; a view {213} which, according to certain
observations of his own, is as follows.[241] "I," he says, "in former years
while studying Ptolemy's _Geographia_ discovered that the elevations of the
North pole placed by him in the several regions, fall short of what they
are in our time by one degree and ten minutes: which divergence can by no
means be ascribed to an error of the tables: For it is not credible that
the whole series in the book is equally wrong in the figures of the tables:
Hence it is necessary to allow that the North pole has been tilted toward
the vertical point. Accordingly a lengthy observation has already begun to
disclose to us things hidden from our forefathers; not indeed through any
sloth of theirs, but because they lacked the prolonged observation of their
predecessors: For before Ptolemy very few places were observed with regard
to the elevations of the pole, as he himself also bears witness at the
beginning of his _Cosmographia_: (For, says he) Hipparchus alone hath
handed down to us the latitudes of a few places, but a good many have noted
those of distances; especially those which lie toward sunrise or sunset
were received by some general tradition, not owing to any sloth on the part
of authors themselves, but to the fact that there was as yet no practice of
more exact mathematicks. 'Tis accordingly no wonder, if our predecessors
did not mark this very slow motion: For in one thousand and seventy years
it shows itself to be displaced scarce one degree toward the apex of
dwellers upon the earth. The strait of Gibraltar shows this, where in
Ptolemy's time the North pole appears elevated 36 degrees and a quarter
from the Horizon: whereas now it is 37 and two-fifths. The like divergence
is also shown at Leucopetra in Calabria, and at particular spots in Italy,
namely those which have not changed from Ptolemy's time to our own. And so
by reason of this movement, places now inhabited will some day become
deserted, while those regions which are now parched at the torrid zone
will, though long hence, be reduced to our temper of climate. Thus, as in a
course of three hundred and ninety five thousands of years, is that very
slow movement completed." Thus, according to these observations of
Dominicus Maria, the North pole is at a higher elevation, and the latitudes
of places are greater than formerly; whence he argues a change of
latitudes. Now, however, Stadius, taking just the contrary view, proves by
observations that the latitudes have decreased. For he says: "The latitude
of Rome in Ptolemy's _Geographia_ is 41 degrees 2/3: and that you may not
suppose any error of reckoning to have crept in on the part of Ptolemy, on
the day of the Æquinox in the city of Rome, the ninth part of the gnomon of
the sun-dial is lacking in shadow, as Pliny relates and Vitruvius
witnesseth in his ninth book." But the observation of moderns (according to
Erasmus Rheinholdus) gives the same in our time as 41 degrees with a sixth:
so that you are in doubt as to half of one degree in {214} the centre of
the world, whether you show it to have decreased by the earth's obliquity
of motion. One may see then how from inexact observations men rashly
conceive new and contradictory opinions and imagine absurd motions of the
mechanism of the earth. For since Ptolemy only received certain latitudes
from Hipparchus, and did not in very many places make the observations
himself; it is likely that he himself, knowing the position of the places,
formed his estimate of the latitude of cities from probable conjecture
only, and then placed it in the maps. Thus one may see, in the case of our
own Britain, that the latitudes of cities are wrong by two or three
degrees, as experience teaches. Wherefore all the less should we from those
mistakes infer a new motion, or let the noble magnetick nature of the earth
be debased for an opinion so lightly conceived. Moreover, those mistakes
crept the more readily into geography, from the fact that the magnetick
virtue was utterly unknown to those geographers. Besides, observations of
latitudes cannot be made sufficiently exactly, except by experts, using
also finer instruments, and taking into account the refraction of the
lights.
* * * * *
CHAP. III.
On the magnetick diurnal revolution of the Earth's
globe, as a probable assertion against the time-honoured
_opinion of a Primum Mobile_.
Among the ancients Heraclides of Pontus and Ecphantus, afterwards the
Pythagoreans, as Nicetas of Syracuse and Aristarchus of Samos, and some
others (as it seems), used to think that the earth moves, and that the
stars set by the interposition of the earth and rose by her retirement. In
fact they set the earth moving and make her revolve around her axis from
west to east, like a wheel turning on its axle. Philolaus the
Pythagorean[242] would have the earth to be one of the stars, and believed
that it turned in an oblique circle around fire, just as the sun and moon
have their own courses. He was a distinguished mathematician, and a most
able investigator of nature. But after Philosophy became a subject treated
of by very many and was popularized, theories adapted to the vulgar
intelligence or based on sophistical subtility occupied the minds of most
men, and prevailed like a torrent, the multitude consenting. Thereupon many
valuable discoveries of the ancients were rejected, and were dismissed to
perish in banishment; or at least by not being further cultivated and
developed became obsolete. So that Copernicus[243] (among later
discoverers, a man most deserving of literary honour) is the first who
attempted to illustrate the [Greek: phainomena] of {215} moving bodies by
new hypotheses: and these demonstrations of reasons others either follow or
observe in order that they may more surely discover the phænomenal harmony
of the movements; being men of the highest attainments in every kind of
learning. Thus supposed and imaginary orbs of Ptolemy and others for
finding the times and periods of the motions are not necessarily to be
admitted to the physical inquiries of philosophers. It is then an ancient
opinion and one that has come down from old times, but is now augmented by
important considerations that the whole earth rotates with a daily
revolution in the space of 24 hours. Well then, since we see the Sun and
Moon and other planets and the glory of all the stars approach and retire
within the space of one natural day, either the Earth herself must needs be
set in motion with a diurnal movement from West to East, or the whole
heaven and the rest of nature from East to West. But, in the first place,
it is not likely that the highest heaven and all those visible splendours
of the fixed stars are impelled along that most rapid and useless course.
Besides, who is the Master who has ever made out that the stars which we
call fixed are in one and the same sphere, or has established by reasoning
that there are any real and, as it were, adamantine sphæres? No one has
ever proved this as a fact; nor is there a doubt but that just as the
planets are at unequal distances from the earth, [244]so are those vast and
multitudinous lights separated from the Earth by varying and very remote
altitudes; they are not set in any sphærick frame or firmament (as is
feigned), nor in any vaulted body: accordingly the intervals of some are
from their unfathomable distance matter of opinion rather than of
verification; others do much exceed them and are very far remote, and these
being located in the heaven at varying distances, either in the thinnest
æther or in that most subtile quintessence, or in the void: how are they to
remain in their position during such a mighty swirl of the vast orbe of
such uncertain substance. There have been observed by astronomers 1022
stars; besides these, numberless others are visible, some indeed faint to
our senses, in the case of others our sense is dim and they are hardly
perceived and only by exceptionally keen eyes, and there is no one gifted
with excellent sight who does not when the Moon is dark and the air at its
rarest, discern numbers and numbers dim and wavering with minute lights on
account of the great distance: hence it is credible both that these are
many and that they are never all included in any range of vision. How
immeasurable then must be the space which stretches to those remotest of
fixed stars! How vast and immense the depth of that imaginary sphere! How
far removed from the Earth must the most widely separated stars be and at a
distance transcending all sight, all skill and thought! How monstrous then
such a motion {216} would be! It is evident then that all the heavenly
bodies set as if in destined places are there formed into sphæres, that
they tend to their own centres, and that round them there is a confluence
of all their parts. And if they have motion, that motion will rather be
that of each round its own centre, as that of the Earth is; or a forward
movement of the centre in an orbit, as that of the Moon: there would not be
circular motion in the case of a too numerous and scattered flock. Of these
stars some situate near the Æquator would seem to be borne around at a very
rapid rate, others nearer the pole to have a somewhat gentler motion,
others, apparently motionless, to have a slight rotation. Yet no
differences in point of light, mass or colours are apparent to us: for they
are as brilliant, clear, glittering and duskish toward the poles, as they
are near the Æquator and the Zodiack: those which remain set in those
positions do not hang, and are neither fixed, nor bound to anything of the
nature of a vault. All the more insane were the circumvolution of that
fictitious _Primum Mobile_, which is higher, deeper, and still more
immeasurable. Moreover, this inconceivable _Primum Mobile_ ought to be
material and of enormous depth, far surpassing all inferior nature in size:
for nohow else could it conduct from East to West so many and such vast
bodies of stars, and the universe even down to the Earth: and it requires
us to accept in the government of the stars a universal power and a
despotism perpetual and intensely irksome. That _Primum Mobile_ bears no
visible body, is nohow recognizable, is a fiction believed in by those
people, accepted by the weak-minded folk, who wonder more at our
terrestrial mass than at bodies so vast, so inconceivable, and so far
separated from us. But there can be no movement of infinity and of an
infinite body, and therefore no diurnal revolution of that vastest _Primum
Mobile_. The Moon being neighbour to the Earth revolves in 27 days; Mercury
and Venus have their own moderately slow motions; Mars finishes a period in
two years, Jupiter in twelve years, Saturn in thirty. And those also who
ascribe a motion to the fixed stars make out that it is completed in 36,000
years, according to Ptolemy, in 25,816 years, according to Copernicus'
observations; so that the motion and the completion of the journey always
become slower in the case of the greater circles. And would there then be a
diurnal motion of that _Primum Mobile_ which is so great and beyond them
all immense and profound? 'Tis indeed a superstition and in the view of
philosophy a fable now only to be believed by idiots, deserving more than
ridicule from the learned: and yet in former ages, that motion, under the
pressure of an importunate mob of philosophizers, was actually accepted as
a basis of computations and of motions, by mathematicians. The motions of
the bodies (namely planets) seem to take place eastward and following the
order of the signs. {217} The common run of mathematicians and philosophers
also suppose that the fixed stars in the same manner advance with a very
slow motion: and from ignorance of the truth they are forced to join to
them a ninth sphære. Whereas now this first and unthinkable _Primum
Mobile_, a fiction not comprehended by any judgment, not evidenced by any
visible constellation, but devised of imagination only and mathematical
hypothesis, unfortunately accepted and believed by philosophers, extended
into the heaven and beyond all the stars, must needs with a contrary
impulse turn about from East to West, in opposition to the inclination of
all the rest of the Universe. Whatsoever in nature is moved naturally, the
same is set in motion both by its own forces and by the consentient compact
of other bodies. Such is the motion of parts to their whole, of all
interdependent sphæres and stars in the universe: such is the circular
impulse in the bodies of the planets, when they affect and incite one
another's courses. But with regard to the _Primum Mobile_ and its contrary
and exceeding rapid movement, what are the bodies which incite it or propel
it? What is the nature that conspires with it? Or what is that mad force
beyond the _Primum Mobile_? Since it is in bodies themselves that acting
force resides, not in spaces or intervals. But he who thinks that those
bodies are at leisure and keeping holiday, while all the virtue of the
universe appertains to the very orbits and sphæres, is on this point not
less mad than he who, in some one else's house, thinks that the walls and
floors and roof rule the family rather than the wife and thoughtful
paterfamilias. Therefore not by the firmament are they borne along, or are
moved, or have their position; much less are those confused crowds of stars
whirled around by the _Primum Mobile_, nor are they torn away and huddled
along by a contrary and extremely rapid movement. Ptolemy of Alexandria
seems to be too timid and weak-minded in dreading the dissolution of this
nether world, were the Earth to be moved round in a circle. Why does he not
fear the ruin of the Universe, dissolution, confusion, conflagration, and
infinite disasters celestial and super-celestial, from a motion
transcending all thoughts, dreams, fables, and poetic licences,
insurmountable, ineffable, and inconceivable? Wherefore we are carried
along by a diurnal rotation of the earth (a motion for sure more
congruous), and as a boat moves above the waters, so do we turn about with
the earth, and yet seem to ourselves to be stationary, and at rest. Great
and incredible it seems to some philosophers, by reason of inveterate
prejudice, that the Earth's vast body should be swirled wholly round in the
space of 24 hours. But it would be more incredible that the Moon should
travel through her orbit, or complete an entire course in a space of 24
hours; more so the Sun or Mars; still more Jupiter and Saturn; more than
marvellous would be the velocity in the case of the {218} fixed stars and
the firmament; what in the world they would have to wonder at in the case
of their ninth sphere, let them imagine as they like. But to feign a
_Primum Mobile_ and to attribute to the thing thus feigned a motion to be
completed in the space of 24 hours, and not to allow this motion to the
Earth in the same interval of time, is absurd. For a great circle of the
Earth is to the ambit of the _Primum Mobile_ less than a furlong to the
whole Earth. If the diurnal rotation of the Earth seem headlong, and not
admissible in nature by reason of its rapidity, worse than insane will be
the movement of the _Primum Mobile_ both for itself and the whole universe,
agreeing as it does with no other motion in any proportion or likeness. It
seems to Ptolemy and the Peripateticks that nature must be disordered, and
the framework and structure of this globe of ours be dissolved, by reason
of so swift a terrestrial revolution. The Earth's diameter is 1718 German
miles; the greatest elongation of the new Moon is 65, the least is 55
semi-diameters of the Earth: the greatest altitude of the half moon is 68,
the least 52: yet it is probable that its sphære is still larger and
deeper. The sun in its greatest eccentricity has a distance of 1142
semi-diameters of the Earth; Mars, Jupiter, Saturn, being slower in motion,
are so proportionately further remote from the Earth. The distances of the
firmament and of the fixed stars seem to the best mathematicians
inconceivable. Leaving out the ninth sphære, if the convexity of the
_Primum Mobile_ be duly estimated in proportion to the rest of the sphæres,
the vault of the _Primum Mobile_ must in one hour run through as much space
as is comprised in 3000 great circles of the Earth, for in the vault of the
firmament it would complete more than 1800; but what iron solidity can be
imagined so firm and tough as not to be disrupted and shattered to
fragments by a fury so great and a velocity so ineffable. The Chaldæans
indeed would have it that the heaven consists of light. In light, however,
there is no so-great firmness, neither is there in Plotinus' fiery
firmament, nor in the fluid or aqueous or supremely rare and transparent
heaven of the divine Moses, which does not cut off from our sight the
lights of the stars. We must accordingly reject the so deep-set error about
this so mad and furious a celestial velocity, and the forced retardation of
the rest of the heavens. Let theologians discard and wipe out with sponges
those old women's tales of so rapid a spinning round of the heavens
borrowed from certain inconsiderate philosophers. The sun is not propelled
by the sphære of Mars (if a sphære there be) and by his motion, nor Mars by
Jupiter, nor Jupiter by Saturn. The sphære, too, of the fixed stars, seems
well enough regulated except so far as motions which are in the Earth are
ascribed to the heavens, and bring about a certain change of phænomena. The
superiors do not exercise a despotism over the inferiors; for the heaven of
{219} philosophers, as of theologians, must be gentle, happy, and tranquil,
and not at all subject to changes: nor shall the force, fury, swiftness,
and hurry of a _Primum Mobile_ have dominion over it. That fury descends
through all the celestial sphæres, and celestial bodies, invades the
elements of our philosophers, sweeps fire along, rolls along the air, or at
least draws the chief part of it, conducts the universal æther, and turns
about fiery impressions (as if it were a solid and firm body, when in fact
it is a most refined essence, neither resisting nor drawing), leads captive
the superior. O marvellous constancy of the terrestrial globe, the only one
unconquered; and yet one that is holden fast, or stationary, in its place
by no bonds, no heaviness, by no contiguity with a grosser or firmer body,
by no weights. The substance of the terrestrial globe withstands and sets
itself against universal nature. Aristotle feigns for himself a system of
philosophy founded on motions simple and compound, that the heavens revolve
in a simple circle, its elements moving with a right motion, the parts of
the earth seeking the earth in straight lines, falling on its surface at
right angles, and tending together toward its centre, always, however, at
rest therein; accordingly also the whole Earth remains immovable in its
place, united and compacted together by its own weight. That cohæsion of
parts and aggregation of matter exist in the Sun, in the Moon, in the
planets, in the fixed stars, in fine in all those round bodies whose parts
cohære together and tend each to their own centres; otherwise the heaven
would fall, and that sublime ordering would be lost: yet these coelestial
bodies have a circular motion. Whence the Earth too may equally have her
own motion: and this motion is not (as some deem it) unsuitable for the
assembling or adverse to the generation of things. For since it is innate
in the terrestrial globe, and natural to it; and since there is nothing
external that can shock it, or hinder it by adverse motions, it goes round
without any ill or danger, it advances without being forced, there is
nothing that resists, nothing that by retiring gives way, but all is open.
For while it revolves in a space void of bodies, or in the incorporeal
æther, all the air, the exhalations of land and water, the clouds and
pendent meteors, are impelled along with the globe circularly: that which
is above the exhalations is void of bodies: the finest bodies and those
which are least cohærent almost void are not impeded, are not dissolved,
while passing through it. Wherefore also the whole terrestrial globe, with
all its adjuncts, moves bodily along, calmly, meeting no resistance.
Wherefore empty and superstitious is the fear that some weak minds have of
a shock of bodies (like Lucius Lactantius, who, in the fashion of the
unlettered rabble and of the most unreasonable men scoffs at an Antipodes
and at the sphærick ordering of the Earth all round). So for these reasons,
not only probable but manifest, does the diurnal rotation of the earth
seem, {220} since nature always acts through a few rather than through
many; and it is more agreeable to reason that the Earth's one small body
should make a diurnal rotation, than that the whole universe should be
whirled around. I pass over the reasons of the Earth's remaining motions,
for at present the only question is concerning its diurnal movement,
according to which it moves round with respect to the Sun, and creates a
natural day (which we call a nycthemeron[245]). And indeed Nature may be
thought to have granted a motion very suitable to the Earth's shape, which
(being sphærical) is revolved about the poles assigned it by Nature much
more easily and fittingly than that the whole universe, whose limit is
unknown and unknowable, should be whirled round; and than there could be
imagined an orbit of the _Primum Mobile_, a thing not accepted by the
ancients, which Aristotle even did not devise or accept as in any shape or
form existing beyond the sphære of the fixed stars; which finally the
sacred scriptures do not recognize any more than they do the revolution of
the firmament.
* * * * *
CHAP. IIII.
That the Earth moves circularly.
If then the philosophers of the common sort, with an unspeakable absurdity,
imagine the whole heaven and the vast extent of the universe to rotate in a
whirl, it yet remains that the earth performs a diurnal change. For in no
third way can the apparent revolutions be explained. This day, then, which
is called natural, is a revolution of some meridian of the Earth from Sun
to Sun. It revolves indeed in an entire course, from a fixed star round to
that star again. Those bodies which in nature are moved with a circular,
æquable and constant motion, are furnished, in their parts, with various
boundaries. But the Earth is not a Chaos nor disordered mass; but by reason
of its astral virtue, it has boundaries which subserve the circular motion,
poles not mathematical, an æquator not devised by imagination, meridians
also and parallels; all of which we find permanent, certain and natural in
the Earth: which by numerous experiments the whole magnetick philosophy
sets forth. For in the earth there are poles set in fixed bounds, and at
them the verticity mounts up on either side from the plane of the Earth's
æquator, with forces which are mightier and præpotent from the common
action of the whole; and with these poles the diurnal revolution is in
agreement. But in no turnings-about of bodies, in none of the motions of
the planets are there to be recognized, beheld, or assured to us by any
reasoning any sensible or natural poles in the firmament, or in any
_Primum_ {221} _Mobile_; but those are the conception of an unsettled
imagination. Wherefore we, following an evident, sensible and tested cause,
do know that the earth moves on its own poles, which are apparent to us by
many magnetick demonstrations. For not only on the ground of its constancy,
and its sure and permanent position, is the Earth endowed with poles and
verticity: for it might be directed toward other parts of the universe,
toward East or West or some other region. By the wondrous wisdom then of
the Builder forces, primarily animate, have been implanted in the Earth,
that with determinate constancy the Earth may take its direction, and the
poles have been placed truly opposite[246], that about them as the termini,
as it were, of some axis, the motion of diurnal turning might be performed.
But the constancy of the poles is regulated by the primary soul. Wherefore,
for the Earth's good, the collimations of her verticities do not
continually regard a definite point of the firmament and of the visible
heaven. For changes of the æquinoxes take place from a certain deflection
of the Earth's axis; yet in regard to that deflection, the Earth has a
constancy of motion [Illustration] derived from her own forces. The Earth,
that she may turn herself about in a diurnal revolution, leans on her
poles. For since at A and B there is constant verticity, and the axis is
straight; at C and D (the æquinoctial line) the parts are free, the whole
forces on either side being spread out from the plane of the æquator toward
the poles, in æther which is free from renitency, or else in a void; and A
and B remaining constant, C revolves toward D both from innate conformity
and aptitude, and for necessary good, and the avoidance of evil; but being
chiefly moved forward by the diffusion of the solar orbes of virtues, and
by their lights. And 'tis borne around, not upon a new and strange course,
but (with the {222} tendency common to the rest of the planets) it tends
from West to East. For all planets have a like motion Eastward according to
the succession of the signs, whether Mercury and Venus revolve beneath the
Sun, or around the Sun. That the Earth is capable of and fitted for moving
circularly its parts show, which when separated from the whole are not only
borne along with the [Illustration] straight movement taught by the
Peripateticks, but rotate also. A loadstone fixed in a wooden vessel is
placed on water so as to swim freely, turn itself, and float about. If the
pole B of the loadstone be set contrary to nature toward the South, F, the
Terrella is turned about its own centre with a circular motion in the plane
of the Horizon, toward the North, E, where it rests, not at C or D. So does
a small stone if only of four ounces; it has the same motion also and just
as quick, if it were a strong magnet of one hundred pounds. The largest
magnetical mountain will possess the same turning-power also, if launched
in a wide river or deep sea: and yet a magnetick body is much more hindered
by water than the whole Earth is by the æther. The whole Earth would do the
same, if the Boreal pole were to be diverted from its true direction; for
the Boreal pole would run back with the circular motion of the whole around
the centre toward the Cynosure. But this motion by which the parts
naturally settle themselves in their own {223} resting-places is no other
than circular. The whole Earth regards the Cynosure with her pole according
to a steadfast law of her nature: and thus each true part of it seeks a
like resting-place in the world, and is moved circularly toward that
position. The natural movements of the whole and of the parts are alike:
wherefore when the parts are moved in a circle, the whole also has the
potency of [Illustration] moving circularly. A sphærical loadstone placed
in a vessel on water moves circularly around its centre (as is manifest) in
the plane of the Horizon, into conformity[247] with the earth.
So also it would move in any other great circle if it could be free; as in
the declination instrument, a circular motion takes place in the meridian
(if there were no variation), or, if there should be some variation, in a
great circle drawn from the Zenith through the point of variation on the
horizon. And that circular motion of the magnet to its own just and natural
position shows that the whole Earth is fitted and adapted, and is
sufficiently furnished with peculiar forces for diurnal circular motion. I
omit what Peter Peregrinus[248] constantly affirms, that a terrella
suspended above its poles on a meridian moves circularly, making an entire
revolution in 24 hours: which, however, it has not happened to ourselves as
yet to see; and we even doubt this motion on account of the weight of the
stone itself, as well as because the whole Earth, as she is moved of
herself, so also is she propelled by other stars: and this does not happen
in proportion (as it does in the terrella) {224} in every part. The Earth
is moved by her own primary form and natural desire, for the conservation,
perfection, and ordering of its parts, toward things more excellent: and
this is more likely than that the fixed stars, those luminous globes, as
well as the Wanderers, and the most glorious and divine Sun, which are in
no way aided by the Earth, or renewed, or urged by any virtue therein,
should circulate aimlessly around the Earth, and that the whole heavenly
host should repeat around the Earth courses never ending and of no profit
whatever to the stars. The Earth, then, which by some great necessity, even
by a virtue innate, evident, and conspicuous, is turned circularly about
the Sun, revolves; and by this motion it rejoices in the solar virtues and
influences, and is strengthened by its own sure verticity, that it should
not rovingly revolve over every region of the heavens. The Sun (the chief
agent in nature) as he forwards the courses of the Wanderers, so does he
prompt this turning about of the Earth by the diffusion of the virtues of
his orbes, and of light. And if the Earth were not made to spin with a
diurnal revolution, the Sun would ever hang over some determinate part with
constant beams, and by long tarriance would scorch it, and pulverize it,
and dissipate it, and the Earth would sustain the deepest wounds; and
nothing good would issue forth; it would not vegetate, it would not allow
life to animals, and mankind would perish. In other parts, all things would
verily be frightful and stark with extreme cold; whence all high places
would be very rough, unfruitful, inaccessible, covered with a pall of
perpetual shades and eternal night. Since the Earth herself would not
choose to endure this so miserable and horrid appearance on both her faces,
she, by her magnetick astral genius, revolves in an orbit, that by a
perpetual change of light there may be a perpetual alternation of things,
heat and cold, risings and settings, day and night, morn and eve, noon and
midnight. Thus the Earth seeks and re-seeks the Sun, turns away from him
and pursues him, by her own wondrous magnetick virtue. Besides, it is not
only from the Sun that evil would impend, if the Earth were to stay still
and be deprived of solar benefit; but from the Moon also serious dangers
would threaten. For we see how the ocean rises and swells beneath certain
known positions of the Moon: And if there were not through the daily
rotation of Earth a speedy transit of the Moon, the flowing sea would be
driven above its level into certain regions, and many shores would be
overwhelmed with huge waves. In order then that Earth may not perish in
various ways, and be brought to confusion, she turns herself about by
magnetick and primary virtue: and the like motions exist also in the rest
of the Wanderers, urged specially by the movement and light of other
bodies. For the Moon also turns herself about in a monthly course, to
receive in succession the Sun's beams in which she, like the Earth, {225}
rejoices, and is refreshed: nor could she endure them for ever on one
particular side without great harm and sure destruction. Thus each one of
the moving globes is for its own safety borne in an orbit either in some
wider circle, or only by a rotation of its body, or by both together. But
it is ridiculous for a man a philosopher to suppose that all the fixed
stars and the planets and the still higher heavens revolve to no other
purpose, save the advantage of the Earth. It is the Earth, then, that
revolves, not the whole heaven, and this motion gives opportunity for the
growth and decrease of things, and for the generating of things animate,
and awakens internal heat for the bringing of them to birth. Whence matter
is quickened for receiving forms; and from the primary rotation of the
Earth natural bodies have their primary impetus and original activity. The
motion then of the whole Earth is primary, astral, circular, around its own
poles, whose verticity arises on both sides from the plane of the æquator,
and whose vigour is infused into opposite termini, in order that the Earth
may be moved by a sure rotation for its good, the Sun also and the stars
helping its motion. But the simple straight motion downwards of the
Peripateticks is a motion of weight, a motion of the aggregation of
disjoined parts, in the ratio of their matter, along straight lines toward
the body of the Earth: which lines tend the shortest way toward the centre.
The motions of disjoined magnetical parts of the Earth, besides the motion
of aggregation, are coition, revolution, and the direction of the parts to
the whole, for harmony of form, and concordancy.
* * * * *
CHAP. V.
Arguments of those denying the Earth's motion, and
_their confutation._
Now it will not be superfluous to weigh well the arguments of those who say
the Earth does not move; that we may be better able to satisfy the crowd of
philosophizers who assert that this constancy and stability of the Earth is
confirmed by the most convincing arguments. Aristotle does not allow that
the Earth moves circularly, on the ground that each several part of it
would be affected by this particular motion; that whereas now all the
separate parts of the Earth are borne toward the middle in straight lines,
that circular motion would be violent, and strange to nature, and not
enduring. But it has been before proved that all actual portions of the
Earth move in a circle, and that all magnetick bodies (fitly disposed) are
borne around in an orbe. They are borne, however, toward the centre of the
Earth in a {226} straight line (if the way be open) by a motion of
aggregation as though to their own origin: they move by various motions
agreeably to the conformation of the whole: a terrella is moved circularly
by its innate forces. "Besides" (says he), "all things which are borne in
an orbe, afterwards would seem to be abandoned by the first motion, and to
be borne by several motions besides the first. The Earth must also be borne
on by two sorts of motion, whether it be situate around a mid-point, or in
the middle site of the universe: and if this were so, there must needs be
at one time an advance, at another time a retrogression of the fixed stars:
This, however, does not seem to be the case, but they rise and set always
the same in the same places." But it by no means follows that a double
motion must be assigned to the Earth. But if there be but one diurnal
motion of the Earth around its poles, who does not see that the stars must
always in the same manner rise and set at the same points of the horizon,
even although there be another motion about which we are not disputing:
since the mutations in the smaller orbit cause no variation of aspect in
the fixed stars owing to their great distance, unless the axis of the Earth
have varied its position, concerning which we raise a question when
speaking of the cause of the præcession of the æquinoxes. In this argument
are many flaws. For if the Earth revolve, that we asserted must needs occur
not by reason of the first sphære, but of its innate forces. But if it were
set in motion by the first sphære, there would be no successions of days
and nights, for it would continue its course along with the _Primum
Mobile_. But that the Earth is affected by a double movement at the time
when it rotates around its own centre, because the rest of the stars move
with a double motion, does not follow. Besides, he does not well consider
the argument, nor do his interpreters understand the same. [Greek: toutou
de sumbainontos, anankaion gignesthai parodous kai tropas tôn endedemenôn
astrôn.] (Arist. _de Coelo_, ii. chap. 14.) That is, "If this be so, there
must needs be changes, and retrogressions of the fixed stars." What some
interpret as retrogressions or regressions, and changes of the fixed stars,
others explain as diversions: which terms can in no way be understood of
axial motion, unless he meant that the Earth moved by the _Primum Mobile_
is borne and turned over other poles diverse even from those which
correspond to the first sphære, which is altogether absurd. Other later
theorists suppose that the eastern ocean ought to be impelled so into
western regions by that motion, that those parts of the Earth which are dry
and free from water would be daily flooded by the eastern ocean. But the
ocean is not acted upon by that movement, since nothing opposes it; and
even the whole atmosphere is carried round: And for that reason in the
Earth's course all the things in the air are not left behind by us nor do
they seem to move toward the West: Wherefore also the clouds {227} are at
rest in the air, unless the force of the winds drive them; and objects
which are projected into the air fall again into their own place. But those
foolish folk who think that towers, temples, and buildings must necessarily
be shaken and overthrown by the Earth's motion, may fear lest men at the
Antipodes should slip off into an opposite orbe, or that ships when sailing
round the entire [249]globe should (as soon as they have dipped under the
plane of our horizon) fall into the opposite region of the sky. But those
follies are old wives' gossip, and the rubbish of certain philosophizers,
men who, when they essay to treat of the highest truths and the fabrick of
the universe, and hazard anything, can scarce understand aught _ultra
crepidam_. They would have the Earth to be the centre of a circle; and
therefore to rest motionless amid the rotation. But neither the stars nor
the wandering globes move about the Earth's centre: the high heaven also
does not move circularly round the Earth's centre; nor if the Earth were in
the centre, is it a centre itself, but a body around a centre. Nor is it
confident with reason that the heavenly bodies of the Peripateticks should
attend on a centre so decadent and perishable as that of the Earth. They
think that Nature seeks rest for the generation of things, and for
promoting their increase while growing; and that accordingly the whole
Earth is at rest. And yet all generation takes place from motion, without
which the universal nature of things would become torpid. The motion of the
Sun, the motion of the Moon, cause changes; the motion of the Earth awakens
the internal breath of the globe; animals themselves do not live without
motion, and the ceaseless activity of the heart and arteries. For of no
moment are the arguments for a simple straight motion toward the centre,
that this is the only kind in the Earth, and that in a simple body there is
one motion only and that a simple one. For that straight motion is only a
tendency toward their own origin, not of the parts of the Earth only, but
of those of the Sun also, of the Moon, and of the rest of the sphæres which
also move in an orbit. Joannes Costæus, who raises doubts concerning the
cause of the Earth's motion, looking for it externally and internally,
understands magnetick vigour to be internal, active, and disponent; also
that the Sun is an external promotive cause, and that the Earth is not so
vile and abject a body as it is generally considered. Accordingly there is
a diurnal movement on the part of the Earth for its own sake and for its
advantage. Those who make out that that terrestrial motion (if such there
be) takes place not only in longitude, but also in latitude, talk nonsense.
For Nature has set in the Earth determinate poles, and definite unconfused
revolutions. Thus the Moon revolves with respect to the Sun in a monthly
course; yet having her own definite poles, facing determinate parts of the
heaven. To suppose that the air moves the Earth would be {228} ridiculous.
For air is only exhalation, and is an enveloping effluvium from the Earth
itself; the winds also are only a rush of the exhalations in some part near
the Earth's surface; the height of its motion is slight, and in all regions
there are various winds unlike and contrary. Some writers, not finding in
the matter of the Earth the cause (for they say that they find nothing
except solidity and consistency), deny it to be in its form; and they only
admit as qualities of the Earth cold and dryness, which are unable to move
the Earth. The Stoicks attribute a soul to the Earth, whence they pronounce
(amid the laughter of the learned) the Earth to be an animal. This
magnetick form, whether vigour or soul, is astral. Let the learned lament
and bewail the fact that none of those old Peripateticks, nor even those
common philosophizers heretofore, nor Joannes Costæus, who mocks at such
things, were able to apprehend this grand and important natural fact. But
as to the notion that surface inequality of mountains and valleys would
prevent the Earth's diurnal revolution, there is nothing in it: for they do
not mar the Earth's roundness, being but slight excrescences compared with
the whole Earth; nor does the Earth revolve alone without its emanations.
Beyond the emanations, there is no renitency. There is no more labour
exerted in the Earth's motion than in the march of the rest of the Stars:
nor is it excelled in dignity by some stars. To say that it is frivolous to
suppose that the Earth rather seeks a view of the Sun, than the Sun of the
Earth, is a mark of great obstinacy and unwisdom. Of the theory of the
rotation we have often spoken. If anyone seek the cause of the revolution,
or of other tendency of the Earth, from the sea surrounding it, or from the
motion of the air, or from the Earth's gravity, he would be no less silly
as a theorist than those who stubbornly ground their opinions on the
sentiments of the ancients. Ptolemy's reasonings are of no weight; for when
our true principles are laid down, the truth comes to light, and it is
superfluous to refute them. Let Costæus recognize and philosophers see how
unfruitful and vain a thing it becomes then to take one's stand on the
principles and unproved opinions of certain ancients. Some raise a doubt
how it can be that, if the Earth move round its own axis, a globe of iron
or of lead dropped from the highest point of a tower falls exactly
perpendicularly to a spot of the Earth below itself. Also how it is that
cannon balls from a large culverin, fired with the same quantity and
strength of powder, in the same direction and at a like elevation through
the same air, would be cast at a like distance from a given spot both
Eastward and Westward, supposing the Earth to move Eastward. But those who
bring forward this kind of argument are being misled: not attending to the
nature of primary globes, and the combination of parts with their globes,
even though they be not adjoined by solid parts. Whereas the motion of the
Earth in the diurnal revolution does not involve the separation of her more
{229} solid circumference from the surrounding bodies; but all her effluvia
surround her, and in them heavy bodies projected in any way by force, move
on uniformly along with the Earth in general coherence. And this also takes
place in all primary bodies, the Sun, the Moon, the Earth, the parts
betaking themselves to their first origins and sources, with which they
connect themselves with the same appetence as terrene things, which we call
heavy, with the Earth. So lunar things tend to the Moon, solar things to
the Sun, within the orbes of their own effluvia. The emanations hold
together by continuity of substance, and heavy bodies are also united with
the Earth by their own gravity, and move on together in the general motion:
especially when there is no renitency of bodies in the way. And for this
cause, on account of the Earth's diurnal revolution, bodies are neither set
in motion, nor retarded; they do not overtake it, nor do they fall short
behind it when violently projected toward East or West.
[Illustration]
Let E F G be the Earth's globe, A its centre, L E the ascending effluvia:
Just as the orbe of the effluvia progresses with the Earth, so also does
the unmoved part of the circle at the straight line L E progress along with
the general revolution. At L and E, a heavy body, M, falls perpendicularly
toward E, taking the shortest way to the centre, nor is that right movement
of weight, or of aggregation compounded with a circular movement, but is a
simple right motion, never leaving the line L E. But when thrown with an
equal force from E toward F, and from E toward G, it completes an equal
distance on either side, even though the daily rotation of the Earth is in
process: just as twenty paces of a man mark an equal space whether toward
East or West: so the Earth's diurnal motion {230} is by no means refuted by
the illustrious Tycho Brahe, through arguments such as these.
[Illustration] The tendency toward its origin (which, in the case of the
Earth, is called by Philosophers weight) causes no resistance to the
diurnal revolution, nor does it direct the Earth, nor does it retain the
parts of the Earth in place, for in regard to the Earth's solidity they are
imponderous, nor do they incline further, but are at rest in the mass. If
there be a flaw in the mass, such as a deep cavity (say 1000 fathoms), a
homogenic portion of the Earth, or compacted terrestrial matter, descends
through that space (whether filled with water or air) toward an origin more
assured than air or water, seeking a solid globe. But the centre of the
Earth, as also the Earth as a whole, is imponderous; the separated parts
tend toward their own origin, but that tendency we call weight; the parts
united are at rest; and even if they were ponderable, they would introduce
no hindrance to the diurnal revolution. For if around the axis A B, there
be a weight at C, it is balanced from E; if at F, from G; if at H, from I.
So internally at L, they are balanced from M: the whole globe, then, having
a natural axis, is balanced in æquilibrio, and is easily set in motion by
the slighted cause, but especially because the Earth in her own place is
nowise heavy nor lacking in balance. Therefore weight neither hinders the
diurnal revolution, nor influences either the direction or continuance in
position. Wherefore it is manifest that no sufficiently strong reason has
yet been found out by Philosophers against the motion of the Earth.
* * * * *
{231} CHAP. VI.
On the cause of the definite time, of an entire
_rotation of the Earth._
Diurnal motion is due to causes which have now to be sought, arising from
magnetick vigour and from the confederated bodies; that is to say, why the
diurnal rotation of the Earth is completed in the space of twenty-four
hours. For no curious art, whether of Clepsydras or of sand-clocks, or
those contrivances of little toothed wheels which are set in motion by
weights, or by the force of a bent steel band, can discover any degree of
difference in the time. But as soon as the diurnal rotation has been gone
through, it at once begins over again. But we would take as the day the
absolute turning of a meridian of the Earth, from sun to sun. This is
somewhat greater than one whole revolution of it; in this way the yearly
course is completed in 365 and nearly ¼ turnings with respect to the sun.
From this sure and regular motion of the Earth, the number and time of 365
days, 5 hours, 55 minutes, in solar tropical years is always certain and
definite, except that there are some slight differences due to other
causes. The Earth therefore revolves not fortuitously, or by chance, or
precipitately; but with a rather high intelligence, equably, and with a
wondrous regularity, in no other way than all the rest of the movable
stars, which have definite periods belonging to their motions. For the Sun
himself being the agent and incitor of the universe in motion, other
wandering globes set within the range of his forces, when acted on and
stirred, also regulate each its own proper courses by its own forces; and
they are turned about in periods corresponding to the extent of their
greater rotation, and the differences of their effused forces, and their
intelligence for higher good. And for that cause Saturn, having a wider
orbit, is borne round it in a longer time, Jupiter a shorter, and Mars
still less; while Venus takes nine months, Mercury 80 days, on the
hypotheses of Copernicus; the Moon going round the Earth with respect to
the Sun in 29 days, 12 hours, 44 minutes. We have asserted that the Earth
moves circularly about its centre, completing a day by an entire revolution
with respect to the Sun. The Moon revolves in a monthly course around the
Earth, and, repeating a conjunction with the Sun after a former synodic
conjunction, constitutes the month or Lunar day. The Moon's mean
concentrick orbit, according to numerous observations of Copernicus and
later astronomers, is found to be distant 29 and about 5/6 diameters of the
Earth from the Earth's centre. The Moon's revolution with respect to the
Sun takes place in 29½ days and 44 minutes of time. We reckon the motion
with respect to the sun, not the periodic motion, {232} just as a day is
one entire revolution of the Earth with respect to the Sun, not one
periodick revolution; because the Sun is the cause of lunar as of
terrestrial motion: also, because (on the hypotheses of later observers)
the synodical month is truly periodic, on account of the Earth's motion in
a great orbit. The proportion of diameters to circumferences is the same.
And the concentrick orbit of the Moon contains twice over 29 and ½ great
circles of the Earth & a little more. The Moon & the Earth, then, agree
together in a double proportion of motion; & the Earth moves in the space
of twenty-four hours, in its diurnal motion; because the Moon has a motion
proportional to the Earth, but the Earth a motion agreeing with the lunar
motion in a nearly double proportion. There is some difference in details,
because the distances of the stars in details have not been examined
sufficiently exactly, nor are mathematicians as yet agreed about them. The
Earth therefore revolves in a space of 24 hours, as the Moon in her monthly
course, by a magnetick confederation of both stars, the globes being
forwarded in their movement by the Sun, according to the proportion of
their orbits, as Aristotle allows, _de Coelo_, bk. ii., chap. 10. "It
happens" (he says) "that the motions are performed through a proportion
existing between them severally, namely, at the same intervals in which
some are swifter, others slower," But it is more agreeable to the relation
between the Moon and the Earth, that that harmony of motion should be due
to the fact that they are bodies rather near together, and very like each
other in nature and substance, and that the Moon has more evident effects
upon the Earth than the rest of the stars, the Sun excepted; also because
the Moon alone of all the planets conducts her revolutions, directly
(however diverse even), with reference to the Earth's centre, and is
especially akin to the Earth, and bound to it as with chains. This, then,
is the true symmetry and harmony between the motions of the Earth and the
Moon; not that old oft-besung harmony of coelestial motions, which assumes
that the nearer any sphære is to the _Primum Mobile_ and that fictitious
and pretended rapidest Prime Motion, the less does it offer resistance
thereto, and the slower it is borne by its own motion from west to east:
but that the more remote it is, the greater is its velocity, and the more
freely does it complete its own movement; and therefore that the Moon
(being at the greatest distance from the _Primum Mobile_) revolves the most
swiftly. Those vain tales have been conceded in order that the _Primum
Mobile_ may be accepted, and be thought to have certain effects in
retarding the motions of the lower heavens; as though the motion of the
stars arose from retardation, and were not inherent and natural; and as
though a furious force were perpetually driving the rest of the heaven
(except only the _Primum Mobile_) with frenzied incitations. Much more
likely is it that the stars are borne around symmetrically by their own
forces, with a certain mutual concert and harmony.
* * * * *
{233} CHAP. VII.
On the primary magnetick nature of the Earth,
whereby its poles are parted from the poles
_of the Ecliptick._
Primarily having shown the manner and causes of the diurnal revolution of
the Earth, which is partly brought about from the vigour of the magnetick
virtue, partly effected by the præ-eminence and light of the Sun; there now
follows an account of the distance of its poles from the poles of the
Ecliptick--a supremely necessary fact. For if the poles of the universe or
of the Earth remained fast at the poles of the Zodiack, then the Æquator of
the Earth would lie exactly beneath the line of the Ecliptick, and there
would be no variation in the seasons of the year, no Winter, no Summer, nor
Spring, nor Autumn: but one and the same invariable aspect of things would
continue. The direction of the axis of the Earth has receded therefore from
the pole of the Zodiack (for lasting good) just so far as is sufficient for
the generation and variety of things. Accordingly the declination of the
tropicks and the inclination of the Earth's pole remain perpetually in the
twenty-fourth degree; though now only 23 degrees 28 minutes are counted;
or, as others make out, 29 minutes: But once it was 23 degrees 52 minutes,
which are the extreme limits of the declinations hitherto observed. And
that has been prudently ordained by nature, and is arranged by the primary
excellence of the Earth. For if those poles (of the Earth and the
Ecliptick) were to be parted by a much greater distance, then when the Sun
approached the tropick, all things in the other deserted part of the globe,
in some higher latitude, would be desolate and (by reason of the too
prolonged absence of the Sun) brought to destruction. As it is, however,
all is so proportioned that the whole terrestrial globe has its own varying
seasons in succession, and alternations of condition, appropriate and
needful: either from the more direct and vertical radiation of light, or
from its increased tarriance above the horizon.
Around these poles of the Ecliptick the direction of the poles of the Earth
is borne: and by this motion the præcession of the æquinoxes is apparent to
us.
* * * * *
{234} CHAP. VIII.
On the Præcession of the Æquinoxes, from the magnetick
motion of the poles of the Earth, in the Arctick
_and Antarctick circle of the Zodiack._
Primitive mathematicians, since they did not pay attention to the
inequælities of the years, made no distinction between the æquinoctial, or
solstitial revolving year, and that which is taken from some one of the
fixed stars. Even the Olympick years, which they used to reckon from the
rising of the dogstar, they thought to be the same as those counted from
the solstice. Hipparchus of Rhodes was the first to call attention to the
fact that these differ from each other, and discovered that the year was
longer when measured by the fixed stars than by the æquinox or solstice:
whence he supposed that there was in the fixed stars also some motion in a
common sequence; but very slow, and not at once perceptible. After him
Menelaus, a Roman geometer, then Ptolemy, and long afterward Mahometes
Aractensis, and several more, in all their literary memoirs, perceived that
the fixed stars and the whole firmament proceeded in an orderly sequence,
regarding as they did the heaven, not the earth, and not understanding the
magnetical inclinations. But we shall demomstrate that it proceeds rather
from a certain rotatory motion of the Earth's axis, than that that eighth
sphære (so called) the firmament, or non-moving empyrean, revolves studded
with innumerable globes and stars, whose distances from the Earth have
never been proved by anyone, nor can be proved (the whole universe gliding,
as it were). And surely it should seem much more likely that the
appearances in the heavens should be clearly accounted for by a certain
inflection and inclination of the comparatively small body of the Earth,
than by the setting in motion of the whole system of the universe;
especially if this motion is to be regarded as ordained solely for the
Earth's advantage: While for the fixed stars, or for the planets, it is of
no use at all. For this motion the rising and settings of stars in every
Horizon, as well as their culminations at the height of the heavens, are
shifted so much that the stars which once were vertical are now some
degrees distant from the zenith. For nature has taken care, through the
Earth's soul or magnetick vigour, that, just as it was needful in
tempering, receiving, and warding off the sun's rays and light, by suitable
seasons, that the points toward which the Earth's pole is directed should
be 23 degrees and more {235} from the poles of the Ecliptick[250]: so now
for moderating and for receiving the luminous rays of the fixed stars in
due turn and succession, the Earth's poles should revolve at the same
distance from the Ecliptick at the Ecliptick's arctick circle; or rather
that they should creep at a gentle pace, that the actions of the stars
should not always remain at the same parallel circles, but should have a
rather slow mutation. For the influences of the stars are not so forceful
as that a swifter course should be desired. Slowly, then, is the Earth's
axis inflected; and the stars' rays, falling upon the face of the Earth,
shift only in so long a time as a diameter of the arctick or polar circle
is extended: whence the star at the extremity of the tail of the Cynosure,
which once was 12 degrees 24 minutes (namely, in the time of Hipparchus)
distant from the pole of the universe, or from that point which the pole of
the Earth used to face, is now only 2 degrees and 52 minutes distant from
the same point; whence from its nearness it is called by the moderns
_Polaris._ Some time it will be only ½ degree away from the pole: afterward
it will begin to recede from the pole until it will be 48 degrees distant;
and this, according to the Prutenical tables, will be in Anno Domini 15000.
Thus _Lucida Lyræ_ (which to us southern Britons now almost culminates)
will some time approach to the pole of the world, to about the fifth
degree. So all the stars shift their rays of light at the surface of the
Earth, through this wonderful magnetical inflection of the Earth's axis.
Hence come new varieties of the seasons of the year, and lands become more
fruitful or more barren; hence the characters and manners of nations are
changed; kingdoms and laws are altered, in accordance with the virtue of
the fixed stars as they culminate, and the strength thence received or lost
in accordance with the singular and specifick nature of each; or on account
of new configurations with the planets in other places of the Zodiack; on
account also of risings and settings, and of new concurrences at the
meridian. The Præcession of the æquinoxes arising from the aequable motion
of the Earth's pole in the arctick circle of the Zodiack is here
demonstrated. Let A B C D be the Ecliptick line; I E G the arctic circle of
the Zodiack. Then if the Earth's pole look to E, the æquinoxes are at D, C.
Let this be at the time of Metho, when the horns of Aries were in the
æquinoctial colure. Now if the Earth's pole have advanced to I; then the
æquinoxes will be at K, L; and the stars in the ecliptick C will seem to
have progressed, in the order of the signs, along the whole arc K C: L will
be moved on by the præcession, against the order of the signs, along the
arc D L. But this would occur in the contrary order, if the point G were to
face the poles of the earth, and the motion were from E to G: for then the
æquinoxes would be M N, and the fixed stars would anticipate the same at C
and D, counter to the order of the signs.
[Illustration]
* * * * *
{236} CHAP. IX.
On the anomaly of the Præcession of the Equinoxes,
_and of the obliquity of the Zodiack._
At one time the shifting of the æquinoxes is quicker, at another slower,
being not always equal: because the poles of the earth travel unequally in
the arctick and antarctick circle of the Zodiack; and decline on both sides
from the middle path: whence the obliquity of the Zodiack to the Æquator
seems to change. And as this has become known by means of long
observations, so also has it been perceived, that the true æquinoctial
points have been elongated from the mean æquinoctial points, on this side
and on that, by 70 minutes (when the prostaphæresis is greatest): but that
the solstices either approach the equator unequally 12 minutes nearer, or
recede as far behind; so that the nearest approach is 23 degrees 28
minutes, and the greatest elongation 23 degrees 52 minutes. Astronomers
have given various explanations to account for this inequality of the
præcession and also of the obliquity of the tropicks. Thebit, with the view
of {237} laying down a rule for such considerable inequalities in the
motion of the stars, explained that the eighth sphære does not move with a
continuous motion from west to east; but is shaken with a certain motion of
trepidation, by which the first points of Aries and Libra in the eighth
heaven describe certain small circles with diameters equal to about nine
degrees, around the first points of Aries and Libra in the ninth sphære.
But since many things absurd and impossible as to motion follow from this
motion of trepidation, that theory of motion is therefore long since
obsolete. Others therefore are compelled to attribute the motion to the
eighth sphære, and to erect above it a ninth heaven also, yea, and to pile
up yet a tenth and an eleventh: In the case of mathematicians, indeed, the
fault may be condoned; for it is permissible for them, in the case of
difficult motions, to lay down some rule and law of equality by any
hypotheses. But by no means can such enormous and monstrous celestial
structures be accepted by philosophers. And yet here one may see how hard
to please are those who do not allow any motion to one very small body, the
Earth; and notwithstanding they drive and rotate the heavens, which are
huge and immense above all conception and imagination: I declare that they
feign the heavens to be three (the most monstrous of all things in Nature)
in order that some obscure motions forsooth[251] may be accounted for.
Ptolemy, who compares with his own the observations of Timocharis and
Hipparchus, one of whom flourished 260 years, the other 460 years before
him, thought that there was this motion of the eighth sphære, and of the
whole firmament; and proved by help of numerous phenomena that it took
place over the poles of the Zodiack, and, supposing its motion to be so far
æquable, that the non-planetary stars in the space of 100 years completed
just one degree beneath the _Primum Mobile_. After him 750 years
Albategnius discovered that one degree was completed in a space of 66
years, so that a whole period would be 23,760 years. Alphonsus made out
that this motion was still slower, completing one degree and 28 minutes
only in 200 years; and that thus the course of the fixed stars went on,
though unequally. At length Copernicus, by means of the observations of
Timocharis, Aristarchus of Samos, Hipparchus, Menelaus, Ptolemy, Mahometes
Aractensis, Alphonsus, and of his own, detected the anomalies of the motion
of the Earth's axis: though I doubt not that other anomalies also will come
to light some ages hence. So difficult is it to observe motion so slow,
unless extending over a period of many centuries; on which account we still
fail to understand the intent of Nature, what she is driving after through
such inequality of motion. Let A be the pole of the Ecliptick, B C the
Ecliptick, D the Æquator; when the pole of the Earth near the arctick
circle of the Zodiack faces the point M, then there is an anomaly of the
præcession of the æquinox at F; {238} but when it faces N, there is an
anomaly of the præcession at E. But when it faces I directly, then the
maximum obliquity G is observed at the solstitial colure; but when it faces
L, there is the minimum obliquity H at the solstitial colure.
[Illustration]
_Copernicus' contorted circlet in the Arctick circle of the Zodiack._
Let F B G be the half of the Arctick circle described round the pole of the
Zodiack: A B C the solstitial colure: A the pole of the Zodiack; D E the
anomaly of longitude 140 minutes at either side on both ends: B C the
anomaly of obliquity 24 minutes: B the greater obliquity of 23 degrees 52
minutes: D the mean obliquity of 23 degrees 40 minutes: C the minimum
obliquity of 23 degrees 28 minutes.
{239} [Illustration]
[Illustration]
{240} The period of motion of the præcession of the æquinoxes is 25,816
Ægyptian years; the period of the obliquity of the Zodiack is 3434 years,
and a little more. The period of the anomaly of the præcession of the
æquinoxes is 1717 years, and a little more. If the whole time of the motion
AI were divided into eight equal parts: in the first eighth the pole is
borne somewhat swiftly from A to B; in the second eighth, more slowly from
B to C; in the third, with the same slowness from C to D; in the fourth,
more swiftly again from D to E; in the fifth, with the same swiftness from
E to F; again more slowly from F to G; and with the same slowness from G to
H; in the last eighth, somewhat swiftly again from H to I. And this is the
contorted circlet of Copernicus, fused with the mean motion into the curved
line which is the path of the true motion. And thus the pole attains the
period of the anomaly of the præcession of the æquinoxes twice; and that of
the declination or obliquity once only. It is thus that by later
astronomers, but especially by Copernicus (the Restorer of Astronomy)[252],
the anomalies of the motion of the Earth's axis are described, so far as
the observations of the ancients down to our own times admit; but there are
still needed more and exact observations for anyone to establish aught
certain about the anomaly of the motion of the præcessions, and at the same
time that also of the obliquity of the Zodiack. For ever since the time at
which, by means of various observations, this anomaly was first observed,
we have only arrived at half a period of the obliquity. So that all the
more all these matters about the unequal motion both of the præcession and
of the obliquity are uncertain and not well known: wherefore neither can we
ourselves assign any natural causes for it, and establish it for certain.
Wherefore also do we to our reasonings and experiments magnetical here set
an end and period.[253]
[Illustration]
* * * * *
{241}
INDEX.
Abano, Pietro di (Apponensis or Apianus), 2.
Abbas, Hali ('Alí ibn Al 'Abb[=a]s, _Al Majúsi_, 2, 6.
Abohalis, 47. _See also_ Avicenna.
_aciarium_ or _acies_, also _aciare_, 18, 23, 33, 36.
Acosta, Josephus, 5.
adamant, 11.
æquator, the magnetick, 13, 79.
Aetius Amidenus, 2.
Affaytatus, Fortunius, 6.
agate, non electrick, 51, 53.
Agricola, Georgius, 2, 3, 10, 19, 26, 111, 112.
Agrippa, H. Cornelius, 3.
_aimant_, 11.
Albategnius (Muhammad ibn J[=a]bir, _Al-Batt[=a]ni_, 237.
Albertus Magnus, 2, 7, 18, 111.
Alexander Aphrodiseus, 3, 48, 92.
Alexandria, Hero of, 58.
Alfonso, Diego, 178.
Alfonsus the Wise (Alphonsus X.), 237.
Amalfians said to have first constructed the compass, 4.
Amatus Lusitanus, 2.
amber, 47, 49-60, 85, 112, 116.
amethyst, electrical properties of, 48.
amianth, 11.
Amidenus, Aetius, 2.
amphitane, 111.
Anatolismus, or Northeasting, 167.
Anaxagoras, 61, 208.
Andrea Doria (Admiral), 4.
Antonius de Fantis, 107.
Antonius Musa Brasavolus, 2.
Antony, the denarius of, 110.
Apianus. _See_ Abano.
Apponensis. _See_ Abano.
Aquinas, Thomas, 3, 64.
Aractensis, Mahometes, 234, 237.
Archelaus, 208.
Ardoynis, Santes de, 2.
Arias Montanus, 4.
Aristarchus, 214, 237.
Aristotle:
_De Anima_, 1, 11, 61, 210.
_De Coelo_, 226, 232.
_De Mirabilibus Auscultationibus_, 22.
_Meteorologica_, 35, 39.
on material of the metals, 19, 20.
on the element of earth, 43.
on motions, 45, 219, 225.
on primary form, 65.
on the _Primum Mobile_, 220.
on animate nature of planets, 208.
armature, 87.
armed loadstones, 86, 87, 88, 89.
Arnaldus de Villa nova, 2, 7.
Arsinoe, Temple of, 2.
Attraction, 46, 60, 64, 68, 90, 98, 109.
Avicenna (Abu 'Ali Husain ibn 'Abd Allah, _Ibn Síná_; also called
Abohalis):
writes on the magnet, 2.
on falling masses of iron, 26.
alleges loadstone an antidote to iron poison, 35.
on the property of attraction, 49.
Augsburgers (Augustani), the, prescribe loadstone in plaster, 33.
axis, the magnetick, 13, 81, 212.
Azores, variation of compass at the, 4, 154, 156, 167.
Bacon, Roger, 5.
Bambola, or Bilbilis, 23.
Baptista Montanus, 2.
Baptista Porta. _See_ Porta.
Barbarus, Hermolaus, 3.
Barlowe, William (Rev. Archdeacon), his book, _The Navigators Supply_, 8.
basil leaves alleged not to be attracted, 48.
belemnites are electrical, 48.
Bencora (Th[=a]bit ibn Kurrah, _Al Harrani_; also called Thebitius), 117,
236.
Benedictus, Joannes Baptista (Giambattista Benedetti), 167.
beryl, electrick properties of, 48.
Bessardus (Toussaincte de Bessard), 5, 116, 153.
Blondus, Flavius, the historian, 4.
Borough, William, his book on the _Variation of the Compass_, 8.
Borrholybicum (North-north-west), 160.
Brahe, Tycho, 174, 229.
Brandoe, the island of, 181.
Brasavolus, Antonius Musa, 2.
Bristolla, or Bristol gem, 48.
burnt clay, magnetick properties of, 26, 43.
{242}
Cabot, Sebastian, 4.
Cælius Calcagninus, 7.
Cæsare, or Cesare, Giulio, 141.
Calaber, Hannibal Rosetius, 3,
_calamita_ or _kalamita_, 11.
Calcagninus, Cælius, 7.
Camillus Leonhardus, 3.
Candish, or Cavendish, Thomas, *iij, 117.
cap of iron for a loadstone, 86, 89, 90, 95.
_carabe_, or _karabe_, 47.
carbuncle, electrick properties of, 48, 111.
Cardan, Hieronymo, 2.
_De Proportionibus_:
on iron and earth, 43, 62, 67.
on distance of centre of cosmos, 169.
_De Rerum Varietate_:
on fall of meteorick iron, 26.
on attraction of amber, 49.
on a perpetual motion engine, 107.
_De Subtilitate_:
alleges magnet to feed on iron, 37, 63, 92.
on magnet that draws silver, 110.
on magnetick influence of star in tail of _Ursa Minor_, 5, 116, 153.
carnelian, the, 51, 55.
_catoblepas_, the antelope called, 63.
Cesare, Giulio, 141.
_chalybs_, 18, 25, 33.
chatochitis, 111.
chemists, the, 19, 20, 21, 24, 37, 66.
China, 4, 8, 9, 11, 17, 32, 119.
Chinocrates, 2.
circumpulsion, doctrine of, 3, 61.
clamps (open kilns), 26.
clay when burnt is magnetick, 26, 43, 97.
clepsydra, 231.
Coimbra, College of, 5.
coition (mutual attraction), 45, 46, 60, 65, 67, 68, 81, 98, 99, 103,
109, 131.
definition of, *vj, 68.
orbe of, *vj.
colours of loadstones, 9, 10, 27.
Como, 23.
compass, alleged invention of, by Amalfians, 4.
origin of the compass-card, 4, 165.
the mariners' (_pyxis_), 3, 115, 147, 165, 172.
the little (_pyxidula_), 181, 202.
different forms of, Italian, Baltic, Portuguese, English, 165, 166,
177, 181.
conduction, magnetick, 85, 104, 125.
consequent poles, 129, 142.
Copernican system, 231.
Copernicus, Nicolas, 212, 214, 216, 231, 237, 238, 240.
Cordus, Valerius, 10.
Cornelius Agrippa, 3.
Cornelius Gemma, 63.
Cornelius Tacitus, 25.
_corolla insorta_, or contorted circlet, 238, 240.
Cortes, Martin, 5, 116, 152.
Corvo, Island of, 167.
Costa, Filippo (of Mantua), 141.
Costæus, Joannes, 3, 62, 227, 228.
_creagus_, the, or flesh-magnet, 110.
crystal, rock, 48, 52, 59, 111
Curtius, Nicolaus, 35.
Cusan (Michael Khrypffs), Cardinal de Cusa, 3, 64, 108.
Cynosure, the, or Pole-star, 14, 81, 117, 222, 235.
Dean, Forest of, loadstone found in the, 11.
decay of the magnetick virtue, 18, 37, 124, 138, 149.
declination, the, or dip, 184.
denarius of Antony, 110.
diamond, an electrick, 48, 50, 59, 111.
alleged power to attract iron, 109, 112.
alleged antipathy to magnet, 2, 7, 109, 143.
experiments upon, 143.
Diego Alfonso, 178.
Differences between electricks and magneticks, 47, 60, 65.
Dioscorides, 1, 2, 9, 32.
dip, the, also called declination, 8, 46, 184-204.
dipping-needle, or declination instrument, 185, 203.
direction, or directive force, 41, 46, 115, 119.
dividing a loadstone, 16, 72, 100, 121, 122, 127, 130, 136, 145, 146.
Dominicus Maria Ferrariensis, 212, 213.
Doria, Andrea (Admiral), 4.
Drake, Sir Francis, *iij _bis_, 117.
Du Puys (also called Puteanus), 3, 63.
Earth, the, a great magnet, 38, 39, 40, 41, 44, 119, 211.
_echeneis_ (the sucking fish), 7, 63, 110.
Ecphantus, 214.
effluvia, electrical, 52, 53, 59, 66.
magnetical, 61.
electrical attraction, 50, 51, 111.
electrick force, definition of, 52.
electricks, *vj, 46-60.
_electrum_ ([Greek: êlektron]), 47.
emerald is non-electrick, 51.
emery, 22, 51.
Empedocles, 208.
Encelius (or Entzelt, Christoph.), 3, 111.
Epicurius, 61, 62.
Erasmus Rheinholdus, 213.
Erastus, Thomas, 3, 22.
errors in navigation, 166, 177.
Evax, King of Arabia, 111.
Euripides, 9, 11, 18.
{243}
Fallopius, Gabriellus, 3, 34, 35, 112.
Fantis, Antonius de, 107.
Fernelius, Joannes Franciscus, 4.
Ficinus, Marsilius (or Marsiglio Ficino), 3, 7, 116 153.
filings of iron, 37, 69, 90, 91, 92, 104.
Filippo Costa. _See_ Costa.
fire destroys magnetick properties, 66, 67, 91, 124.
flame destroys electrification, 59.
flame hinders not magnetick attractions, 66.
Flavius Blondus. _See_ Blondus.
flies in amber, 47.
form _versus_ matter, 52, 65.
Fra Paolo, 6.
Fracastorio, Hieronymo, 5, 50, 67, 71, 91, 110, 113, 152.
Franciscus Maurolycus. _See_ Maurolycus.
Franciscus Rueus. _See_ Rueus.
Gagates. _See_ jet.
Galen, 2, 9, 32, 35, 39, 46, 49, 61, 62, 63.
Gallus, Marbodæus, 2, 7.
garlick, its reputed antagonism to magnetism, 2, 32, 64.
Gartias ab Horto, 32.
Gaudentius Merula, 7.
Gauricus, Lucas, 7.
Geber (J[=a]bir ibn Háiyán, _Al-Tarsus[=i]_) 21.
Gemma, Cornelius, 63.
gems, electrick properties of, 48, 51.
_geniter_, 47.
Georgius Agricola. _See_ Agricola.
Gilbert, Adrian, 11.
Gilgil Mauritanus, 19.
Gioia, or Goia, of Amalfi, 4.
Giulio Cæsare, 141.
glass, an electrick by friction, 48, 54, 59.
use of loadstone in making, 111.
goat's blood, 7.
Gonzalus Oviedus, 4.
Goropius, Henricus Becanus, 4.
Grotius, Hugo, 167, 168.
Haematite, 22, 51.
Hali Abbas ('Ali ibn Al 'Abbás, _Al Masúfí_), 2, 6.
Hannibal Rosetius Calaber, 3.
Hariot, Thomas, 7.
Heat, effect of on loadstone, 66, 67, 93, 123, 124.
Helmshuda, 167.
Heraclea, the city of, 8.
Heraclean stone, or stone of Hercules, 8, 43, 61, 169.
Heraclides, 214.
Heraclitus, 208.
Hermes, 209.
Hermolaus Barbarus, 3.
Hero of Alexandria, 58.
Hipparchus, 213, 214, 234, 235, 237.
Hippocrates, 8, 35, 51, 61.
horizon, the magnetick, defined, 80.
Horto, Gartias ab, 32.
Horus, the bone of, or _Os Ori_, 9.
hot iron not magnetick, 66.
Hues, Robert, 7.
Hugo Grotius, 167, 168.
Inclination. _See_ dip.
interposition of bodies, 53, 66, 83, 85, 89, 137.
iris gem, the, 48.
iron, its nature and occurrence, 19, 20, 22, 25.
filings of, 37, 69, 90, 91, 92, 104.
its various names and qualities, 23, 33, 36.
its various uses, 23, 24, 39, 86, 90, 95.
medical uses of, 33, 35.
surpasses loadstone, 69, 95.
verticity in, 85, 123, 139.
iron ore is magnetick, 18, 27, 38, 43.
has poles, 28.
islands, magnetick influence of, 5, 153,161.
Jacobus Severtius, 5.
jet, 47, 48, 53, 55, 86.
Joannes Baptista Porta. _See_ Porta.
Joannes Baptista Montanus, 2.
Joannes Costæus. _See_ Costæus.
Joannes Franciscus Offusius, 46.
Joannes Goia. _See_ Gioia.
Joannes Langius, 3.
Joannes Taisner, or Taisnier. _See_ Taisnier.
Jofrancus Offusius, 46.
Josephus Acosta, 5.
Julius Cæsar Moderatus, 141.
Julius Cæsar Scaliger. _See_ Scaliger.
Kendall, Abraham, 7, 178.
Korrah, Thebitius Ben. _See_ Bencora.
Lactantius, Lucius, 219.
Lagos, Rodriguez de, 177.
Langius, Joannes, 3.
_lapis magnetis_, 8.
_lapis specularis_, muscovy stone, or mica, 11, 48, 52.
latitude in relation to dip, 196, 200.
Leonardus (or Leonhardus), Camillus, 3.
Levinus Lemnius, 3.
{244}
lifting power of loadstones, 86, 89, 97.
lily of the compass, 117, 152, 165, 177.
liquids, electrical attraction of, 55.
attraction on surface of, 57.
Livio Sanuto, 5, 153, 167.
loadstone armed and unarmed, 86, 87, 88.
as medicine, 32.
in plasters, 33.
rock, the, 5, 6, 18, 116, 152.
various names of, 11.
colours of, 9, 10, 27.
various sources of, 8, 25, 32.
London, magnetick variation at, 154, 163.
longitude, magnetick finding at, 166.
long magnets, advantage of, 82, 83, 99, 101
Lucania, fall of meteorick stones in, 26.
Lucas Gauricus, 7.
Lucretius, 2, 3, 8, 49, 61.
Lusitanus, Amatus, 2.
Lynschoten, Hugo van, *iiij.
Magnes, [Greek: magnês], [Greek: magnêtis], 11.
Magnesia, 8.
Magnetick axis of terrella, 81, 212.
axis of earth, 13, 81, 212.
horizon, 80.
meridian, 79, 152.
mountains or rocks, 5, 6, 18, 116, 152.
islands, 5, 153, 161.
motions, the five, 45.
Magnus, Albertus. _See_ Albertus.
Magnus, Olaus, 5, 6.
Mahometes Aractensis, 234, 237.
Mahomet's tomb, 2.
Manardus, Joannes, 35.
Marbodæus Gallus, 2, 7.
Marcellus Empiricus, 2.
Marco Polo (Paulus Venetus), 4.
mariners' compass. _See_ compass.
Mars, saffron of (_Crocus Martis_), 34, 91.
Marsiglio Ficino. _See_ Ficinus.
Martin Cortes, 5, 116, 152.
matter and form, 52, 65.
Matthæus Silvaticus, 3.
Matthiolus, Petrus, 2, 3.
Mauritanus, Gilgil, 19.
Mauritanus, Serapio, 2, 6.
Maurolycus, Franciscus, 5, 42, 153, 180.
medicinal use of iron, 33.
of loadstone, 32.
Medina, Pedro de, 166.
Menelaus, 234, 237.
meridian, magnetick, 79, 152, 163.
Merula, Gaudentius, 7.
meteorick stones, falls of, 26, 27.
mica (or muscovy stone), 11, 48, 52.
[Greek: mikrogê]. _See_ terrella.
moisture stops electrick action, 53, 56.
Montagnana, B., 35.
Montanus, Arias, 4.
Montanus, Joannes Baptista, 2.
Moors, Serapio and the, 6.
mountains, magnetick, 5, 6, 18, 116, 152.
movement of trepidation, 117.
Musa Brasavolus, Antonius, 2.
muscovy stone, 11, 48, 52. _See also_ mica.
myths of the magnet, 2, 3, 5, 6, 7, 18, 32, 63, 107, 109, 110, 111, 116,
143, 153, 228
motions, the various magnetical, 46.
Names of amber, 47.
names of the loadstone, 11.
names given to the magnetick poles, 15, 115, 125, 129.
Nicander of Colophon, 8, 9.
Nicetas, 214.
Nicolas Copernicus, 212, 214, 216, 231, 237, 238, 240
Nicolaus Myrepsus, or Præpositas, 33.
non-electrick bodies, 51, 55.
Nonius, Petrus (Pedro Nuñez), 166.
Norman, Robert, 5, 8, 153, 161, 162.
supposes a point respective, 5, 153, 161, 162.
his _Newe Attractive_, 8.
discoverer of the dip, 8.
Norumbega, the city of, 154.
Nova Zembla, 152, 179.
Offusius, Jofrancus, 46.
Olaus Magnus, 5, 6.
opal becomes electrical, 48.
orbe of virtue, 76, 96, 191, 205
orbes of planets, 208, 215.
Oribasius, 2.
Orpheus, 11, 61, 209.
Oviedus, Gonzalus (Gonzalo Fernandez de Oviedo y Valdès), 4.
Pantarbes, 111.
Paolo (Paulus Æginæ), 35.
Paolo, Rev. Maestro (Fra Paolo Sarpi), 6
Paolo the Venetian (Marco Polo), 4.
Paracelsus (Bombast von Hohenheim).
asserts the stars to attract iron, 3.
his emplastrum of loadstone, 33.
his method of strengthening loadstones, 93.
Parmenides, 208.
pearls are not electrick, 51, 55.
Pedro de Medina, 166.
percussion excites verticity, 139.
Peregrinus, Peter,
his book, 5.
on cause of magnetick direction, 5, 116, 153.
on perpetual motion engine, 107.
affirms a terrella to revolve daily, 223.
{245}
Peripateticks, the, 20, 41, 43, 45, 65, 218, 222, 225, 227, 228.
perpetual motion machine, 107.
Peter Peregrinus. _See_ Peregrinus.
Peter Plancius. _See_ Plancius.
Petrus Apponensis. _See_ Abano, Pietro di.
Petrus Nonius. _See_ Nonius or Nuñez.
Philolaus, 214.
Philostratus, 111.
Pictorio, G., 6, 49.
_piedramant_, 11.
Plancius, Peter, *v _bis._
planets, influence of, 20, 137, 142.
plasters, magnetick, 32, 33.
Plato, 3.
in the _Io_, discusses name and properties of the magnet, 1, 9, 11, 18.
in the _Timæus_, suggests the theory of circumpulsion, 61.
his Atlantis, 159.
on life in the universe, 208.
Pliny (C. Plinius Secundus).
on loadstone fables, 1, 2, 9, 18.
his mistake about Æthiopian loadstones, 17.
on the five kinds of loadstones, 9.
on the alleged discovery of the loadstones, 8.
on the alleged magnetick mountains, 18.
on a locality where loadstone was found, 11.
on the occurrence of iron in Spain, 25.
on the Sagda and the Catochites, 111.
on the silver denarius of Antony, 110.
on the use of loadstone by glass-makers, 111.
on the shadow of a gnomon of a sun-dial at Rome, 213.
Plotinus, 218.
Plutarch, Claudius.
on the garlick fable, 32.
says something flammable exists in amber, 54.
his theory of circumpulsion, 3, 62.
polarity. _See_ verticity.
pole, the, elevation of, 200, 213.
poles, magnetick, of a loadstone, 13, 41, 72, 81, 144.
poles are not points, 12, 41, 72, 96.
Polo, Marco, 4.
Porta, Joannes Baptista (Giambattista della Porta).
his narration of marvels, 6.
on various tempering of iron, 24.
asserts loadstone a mixture of stone and iron, 63.
on his assertion that loadstones have hairs, 66.
asserts vapour to be cause of attraction, 67.
his error as to change of verticity, 73.
suspends iron upwards by a thread, 92.
his error as to centre of the orbe of virtue, 95.
his error as to the polarity which causes repulsion, 102.
his error as to magnetick opposing forces, 103.
experiment with a balance, 108.
his error as to iron being intoxicated, 138.
his error as to iron excited by a diamond, 143.
his error as to the pointing of a magnet, 144.
proportion between loadstone and iron, 149.
his error as to variation and longitude, 166.
præcession of the Æquinoxes, 234, 236.
_primum mobile_, the, 79, 214, 216, 218, 220, 226, 232, 237.
prostaphæresis, 174, 236.
Prutenical Tables, the, 235.
Ptolemæus, Claudius.
on loadstone fables, 2, 32.
on the occurrence of loadstone and of iron, 9,25.
on the dissolution of the earth, 91, 217, 218.
alleged relation of regions with the planets, 137.
on the elevation of the pole at different latitudes, 213, 214.
on the _Primum Mobile_, and the diurnal movement of the stars, 216,
228, 234.
on the anomalies of the earth's motion, 237.
Puteanus, Gulielmus (Du Puys), 3, 63.
pyrimachus (_i.e._, pyrites), 23.
Pythagoras, 57, 208.
_pyxidula_, 4, 181.
_pyxis_, 3, 115, 147, 165, 172.
Radius, the, of the earth's orbit, 218.
Rasis. _See_ Rhazes.
rays of magnetick virtue, 95.
Reinoldus, Erasmus (or Rheinholdus), 213.
_remora_, the (or sucking fish), 7, 63, 110.
resin becomes electrical by friction, 48, 52.
respective points, 5, 153, 161, 162.
reversal of polarity, 101, 137.
revolution of the globe, 46, 81, 91, 220.
repulsion, electrical, denied to exist, 113.
Rhazes (Muhammad ibn Zakar[=i]y[=a]), 34, 35.
rings, on the verticity of, 129.
Rodriguez de Lagos, 177.
Rosetius Calaber, Hannibal, 3.
Ruellius, Joannes, 7.
Rueus, Franciscus (de la Rue), 6.
Saffron of Mars, 34, 91, 93.
sagda, or sagdo, the, 111.
Sanuto, Livio, 5, 153, 167.
sapphire, the, 48.
scales of iron, 22.
Scaliger, Julius Cæsar.
on cause of magnetick direction, 5, 64, 153.
on a fall of meteorick iron, 26.
on preservation of loadstones, 37.
on amber, 47.
on magnetick attraction, 70.
admits the loadstone to have a soul, 68.
on diamond attracting iron, 112.
scoria or slag of iron, 34, 35.
sealing wax is electrical, 48, 53.
Sebastian Cabot. _See_ Cabot.
Serapio, or Serapio Mauritania (Yuhanná ibn Sarapion), 2, 6.
Severtius, Jacobus, 5.
shielding, magnetick, by iron plate, 83, 85.
{246}
_siderites_ ([Greek: sideritês]) 8, 11, 143.
_siegelstein_ 11.
silk suspension for magnetick iron, 29, 30.
Silvaticus, Matthæus, 3.
silver, loadstone for, 109, 110.
similars, doctrine of attraction of, 50, 62.
Simon Stevinus, *v _bis_, 167, 168.
slate, magnetick properties of, 43.
smeargel (emery), 22.
Solinus, Caius Julius, 1, 9, 111.
Solomon the King, 4.
Sotacus, 9.
Stadius, 213.
stars are at various distances, 215.
steel, 23, 39, 69, 71, 93, 95, 147.
Stevinus, Simon, *v _bis_, 167, 168.
_stomoma_ ([Greek: stomôma]) 23, 33, 36.
Strabo, 25.
_succinum_. _See_ amber.
Sudini, or Sudavienses, 47.
sulphur, electrical by friction, 48, 53, 56, 59.
[Greek: sundromê], *vj.
[Greek: sunentelecheia], 68.
Sussex, iron ore in, 22.
sympathy and antipathy, 65, 68, 112.
Tacitus, Cornelius, 25.
Taisner, or Taisnier, Joannes, 5, 107.
Tariassiona or Tarazona, 23.
terrella.
definition of, *vj, 12, 13.
poles and axis of, 13, 72, 81, 144.
divided into two parts, 72.
magnetick vigour, diagram of, 74, 75.
how small pieces of iron behave toward, 75, 76.
orbe of virtue of, 76, 77, 104.
"geography" of, 78.
æquinoctial circle of, 79, 144.
parallels of, 80, 211.
magnetick horizon of, 80.
proportion of the forces in, 81, 82.
experiment with iron sphere, 85.
small iron sphere and rod, 94, 102.
centre of magnetick virtue in, 95.
irregular terrella to exhibit variation, 155, 157.
to illustrate the dip of the needle, 190, 192.
analogy of, with the earth, 41, 78, 119, 211.
testing loadstones, methods of, 108.
Thales of Miletus, 11, 61, 68, 208, 210.
_theamedes_, the, 18.
Thebitius, or Thebit ben Korrah, 117, 236.
Themistius, 71.
Theophrastus, 1, 9, 11.
Thomas Aquinas, 3, 64.
tides, the cause of, 86.
Tycho Brahe, 174, 229.
Variation of the compass, 7, 46, 79, 116, 151-163, 166, 167, 180.
variation at the Azores, 4, 154, 156, 167.
versorium, magnetick, definition of, *vj.
use of, 13, 115, 147.
versorium, non-magnetick, use of, 48, 49, 50.
verticity, 28, 115, 119-147.
acquired, 67, 68, 84, 85, 104, 123, 125, 129, 138, 139, 141, 142, 211.
in iron plates touched by loadstone, 84.
in iron sphere, 85.
how, in iron, 123, 139, 212.
in bracket in tower of St. Augustine's Church, Rimini, 141.
similar at ends of rod touched in middle, 84, 129.
by percussion, 139.
through interposed matter, 67.
not in bodies other than magnetick, 142.
æquator separates two kinds of, 79.
possessed by the earth, as a "Cause," 117.
change of, through change of mass, 72.
definition of, *vj.
described, 119, 120, 121.
destroyed by heat, 66, 93, 124.
earth produces it in loadstone and iron, 42, 140, 211, 212.
excited through greater distances in iron than in air, 104.
exists in all shapes of loadstone, 76.
helps the earth to keep its orbit, 224.
inhærent in wrought iron, 31, 115.
as a magnetick motion, 46.
mutation of, 120, 137.
magnitude of earth prevents variation of, 163, 164.
none acquired by iron rubbed on æquator of terrella, 148.
not affected by position of loadstone, 144.
of one loadstone as affected by another, 69, 138.
opposite, acquired by iron touched by loadstone, 115, 125, 129.
parts having same repel, 122, 133.
pole of, where last contact is, 149.
strengthened in versoria, 147-150.
strength of, decreases at once in both poles, 146.
Villa nova, Arnaldus de, 2, 7.
vincentina, the, 48.
Vincent's Rock, gem of, 54.
Weather affects electricks, 48, 53, 55, 56.
weighing the magnetick force, 108.
Wright, Edward, his prefatory address, *iij _bis_, 7.
wrought iron is magnetick, 29, 139.
Youth preserved by loadstone, 32.
Zeilam, the king of, 32.
Zimiri, 11.
Zoroaster, 209.
{247} THIS TREATISE BY WILLIAM GILBERT, OF COLCHESTER, PHYSICIAN OF LONDON,
ON THE MAGNET, WAS FIRST PUBLISHT IN THE LATIN TONGUE IN LONDON IN THE YEAR
OF OUR LORD M.D.C.; THIS ENGLISH TRANSLATION, WHICH WAS COMPLETED IN THE
YEAR M.C.M., IS PRINTED FOR THE GILBERT CLUB, TO THE NUMBER OF TWO HUNDRED
AND FIFTY COPIES, BY CHARLES WHITTINGHAM AND COMPANY, AT THE CHISWICK
PRESS, TOOKS COURT, CHANCERY LANE, LONDON.
[Illustration]
* * * * *
NOTES
ON THE
DE MAGNETE
OF
DR. WILLIAM GILBERT
[Illustration]
PRIVATELY PRINTED
LONDON MCMI
"For out of olde feldes, as men seith,
Cometh al this newe corn fro yeer to yere;
And out of olde bokes, in good feith,
Cometh al this newe science that men lere."
--_Chaucer._
"I finde that you have vsed in this your tr[=a]slation greate art,
knowledge, and discretion. For walking as it were in golden fetters (as
al Translators doe) you notwithstanding so warilie follow your Auctor,
that where he trippeth you hold him vp, and where he goeth out of the
way, you better direct his foote. You haue not only with the Bee sucked
out the best iuyce from so sweete a flower, but with the Silke-worme as
it were wouen out of your owne bowels, the finest silke; & that which
is more, not rude & raw silke, but finely died with the fresh colour of
your owne Art, Invention, and Practise. If these Adamantes draw you not
to effect this which you haue so happilie begunne: then let these
spurres driue you forward: viz. Your owne promise, the expectation of
your friends, the losse of some credit if you should steppe backe, the
profit which your labours may yeeld to many, the earnest desire which
you yourselfe haue to reviue this Arte, and the vndoubted acceptation
of your paines, if you performe the same."--(Prefatory epistle of John
Case, D. of Physicke, printed in R. Haydocke's translation of _The
Artes of Curious Painting_, of Lomatius, Oxford, 1598.)
"This booke is not for every rude and unconnynge man to see, but for
clerkys and very gentylmen that understand gentylness and
scyence."--_Caxton._
CHISWICK PRESS: CHARLES WHITTINGHAM AND CO.
TOOKS COURT, CHANCERY LANE, LONDON.
* * * * *
{ij}
[Illustration]
BIBLIOGRAPHY OF _DE MAGNETE_.
I. (THE LONDON FOLIO OF 1600.) _Fol. *j. title_ GVILIELMI GIL | berti
colcestren | sis, medici londi- | nensis, | DE MAGNETE, MAGNETI- | cisqve
corporibvs, et de mag- | no magnete tellure; Physiologia noua, | plurimis &
argumentis, & expe- | rimentis demonstrata. | _Printer's Mark_ | Londini |
excudebat Petrvs Short anno | MDC. || _*j verso_ Gilbert's coat of arms. ||
_*ij_ Ad Lectorem || _*iij verso_ Ad gravissimvm doctissimvmqve ... ||
_*vj_ Verborum quorundam interpretatio. || _*vj verso_ Index capitum. || p.
1. GVILIELMI GILBERTI | DE MAGNETE, LIB. I. || p. 240. FINIS. | Errata.
Without any colophon, printer's Mark, or date at end. _Folio. 8 ll. of
preliminary matter._ ABCDEFGHIKLMNOPQRSTV, _all ternions, making 120
numbered leaves. One blank leaf at front and one at end. Page 114 at end of
Liber II. blank. A folded woodcut plate inserted between p. 200 and p. 201.
Woodcut initials, headlines and diagrams. All known copies except one have
ink corrections in several pages, particularly pp. 11, 22, 47._
II. (THE STETTIN QUARTO OF 1628.) _Four preliminary unnumbered leaves,
viz._ (1) _Bastard title_ GULIELMI GILBERTI | Tractatus | DE MAGNETE ||
_verso_ blank; (2) _Engraved title._ TRACTATVS | Siue | PHYSIOLOGIA NOVA |
DE MAGNETE, | MAGNETICISQVE CORPO- | RIBVS ET MAGNO MAGNETE | tellure Sex
libris comprehensus | ã | Guilielmo Gilberto Colcestrensi, | Medico
Londinensi | ... Omnia nunc diligenter recognita & emen- | datius quam ante
in lucem edita, aucta & figu- | ris illustrata operâ & studio | Wolfgangi
LOCHMANS I.U.D. | & Mathemati: | Ad calcem libri adjunctus est Index Capi-
| tum Rerum et Verborum locupletissimus | EXCVSVS SEDINI | Typis Gotzianis
Sumptibus | _Ioh: Hallervordij._ | Anno MDC.XXVIII || _verso_ blank; (3)
Præfatio; (4) Amicorum Acclamationes (verses) || _verso_ blank. _Sig._ A Ad
Lectorem Candidum. _Sig._ A2 _verso_ Ad Gravissimum Doctissimum[=q] Virum.
_Sig._ B2 Verborum quorundam interpretatio. _Verso_ blank, followed by
twelve engraved plates numbered I. to XII. _Sig._ B3 is numbered as p. 1,
and begins GVILIELMI GILBERTI | DE MAGNETE. | LIBER I. _Sig._ C _begins as
p. 5_; _Sig._ D as p. 13; and so forth. The collation therefore is: 4 ll.
unnumbered, ABCDEFGHIKLMNOPQRSTVXYZAaBbCcDdEeFfGgHhIiKkLlMm, _all fours.
Pagination ends on_ p. 232, _which has Sig._ H_3 _in error for_ Hh_3,
_being the end of the text. Verso of_ Hh_3 blank. Index capitum _begins
fol._ [Hh_4] _and_ with Index Verborum _continues to verso of_ Mm_3. _Last
leaf_ [Mm_4] _contains Errata, and instructions to binder to place plates:
verso_ blank. _Quarto. Woodcut initials and diagrams. Without any colophon,
printer's Mark, or date at end._ In some copies the engraved title differs,
having the words _Ioh: Hallervordij._ replaced by the word _Authoris_.
{iij} III. (THE STETTIN QUARTO OF 1633.) _Four preliminary unnumbered
leaves_, viz., (1) _title._ Tractatus, sive Physiologia Nova | de |
MAGNETE, | Magneticisq; corporibus & magno | Magnate tellure, sex libris
comprehensus, | a GUILIELMO GILBERTO Colce- | strensi, Medico Londinensi. |
... Omnia nunc diligenter recognita, & emendatius quam ante | in lucem
edita, aucta & figuris illustrata, opera & studio D. | WOLFGANGI LOCHMANS,
I.U.D. | & Mathematici. | Ad calcem libri adiunctus est Index capitum,
Rerum & Verborum | locupletissimus, qui in priore æditione desiderabatur |
SEDINI, | Typis GOTZIANIS. | ANNO M.DC. XXXII. || _verso_ blank; (2)
Præfatio; (3) Amicorum acclamationes (verses) || _verso_ Claudianus de
Magnete (verses); (4) _ibid._ _Sig._ A Ad Lectorem Candidum. _Sig._ A2
_verso_ Ad Gravissimum Doctissimumq. Virum. _Sig._ B2 Verborum quorundam
interpretatio; _verso_ blank. _Sig._ B3 is numbered as p. 1, and begins
GVILIELMI GILBERTI | DE MAGNETE. | LIBER I. _Sig._ C begins as p. 5; _Sig._
D as p. 13; and so forth. The Collation therefore is: 4 _ll._ unnumbered, A
_to_ Mm, _all fours_. Pagination _ends on p. 232, which bears Sig._ H3 _in
error for_ Hh3. _Verso of Sig._ Hh3. Errata. Index capitum _begins_ Hh4,
_and with_ Index Verborum _extends to verso_ of Mm3. _The last leaf_ [Mm4]
_bears the Instructions to binder, with verso_ blank. _There is no
colophon, printer's Mark, or date at end. Quarto. Woodcut initials, and
diagrams. Twelve etched plates of various sizes inserted._
With the exception of the preliminary matter and the Instructions to
binder, the pagination is the same as in the edition of 1628, the pages in
the body of the work being reprinted word for word; though with exceptions.
For example, p. 18 in Ed. 1633 is one line shorter than in Ed. 1628. The
etched plates are entirely different. It has been thought from the
pagination being alike that these two editions were really the same with
different plates, titles, and preliminary matter. But they are really
different. The spacing of the words, letters and lines is different
throughout, and there are different misprints. The watermarks of the paper
also differ.
IV. (THE BERLIN "FACSIMILE" FOLIO OF 1892.) This is a photozincograph
reproduction of the London folio of 1600. It lacks the ink emendations on
pages 11, 22, 47, &c., found in the original, and is wanting also in some
of the asterisks in the margins.
V. (THE AMERICAN TRANSLATION OF 1893.) Frontispiece portrait || _p. i.
title_ WILLIAM GILBERT | OF COLCHESTER, | physician of London, | on the |
Loadstone and Magnetic Bodies, | and on | the great magnet the earth. | A
new Physiology, | demonstrated with many arguments and experiments. | A
translation by | P. Fleury Mottelay, | ... | New York: | John Wiley & Sons,
| 53 East Tenth Street | 1893. || _p. ii_ bears imprint of Ferris Bros.
_Printers_, 326 Pearl Street, New York. || _p. iii._ reduced reproduction
of title of 1600 edition || _verso_ the Gilbert arms || _p. v._
Translator's Preface || _p. ix._ Biographical Memoir || _p. xxxi._ Contents
|| _p. xxxvii._ Address of Edward Wright || _p. xlvii._ Author's Preface.
|| _p. liii._ Explanation of some terms. || pp. 1-358 text of the work. ||
p. 359 reduced reproduction of title of 1628 edition. || p. 360 _ditto_ of
1633 edition. || p. 361 _ditto_ of Gilbert's _De Mundo Nostro_ of 1651. ||
pp. 363 to 368 General Index. || Pages _xxx_, _xlvi_, _lii_, and 362 are
blanks. There are no signatures. Octavo. Diagrams reduced from woodcuts of
the folio of 1600. Some copies bear on title the imprint | London: |
Bernard Quaritch, | 15 Piccadilly. ||
* * * * *
{1} [Illustration]
NOTES ON THE _DE MAGNETE_ OF
DR. WILLIAM GILBERT.
During the work of revising and editing the English translation of _De
Magnete_, many points came up for discussion, requiring critical
consideration, and the examination of the writings of contemporary or
earlier authorities. Discrepancies between the texts of the three known
editions--the London folio of 1600, and the two Stettin quartos of 1628 and
1633 respectively--demanded investigation. Passages relating to astrology,
to pharmacy, to alchemy, to geography, and to navigation, required to be
referred to persons acquainted with the early literature of those branches.
Phrases of non-classical Latin, presenting some obscurity, needed
explanation by scholars of mediæval writings. Descriptions of magnetical
experiments needed to be interpreted by persons whose knowledge of
magnetism enabled them to infer the correct meaning to be assigned to the
words in the text. In this wise a large amount of miscellaneous criticism
has been brought to bear, and forms the basis for the following notes. To
make them available to all students of Gilbert, the references are given to
page and line both of the Latin folio of 1600 and of the English edition of
1900. S. P. T.
[1] _THE GLOSSARY:_
Gilbert's glossary is practically an apology for the introduction into the
Latin language of certain new words, such as the nouns _terrella_,
_versorium_, and _verticitas_, and the adjectival noun _magneticum_, which
either did not exist in classical Latin or had not the technical meaning
which he now assigns to them. His _terrella_, or [Greek: mikrogê], as he
explains in detail on p. 13, is a little magnetic model of the earth, but
in the glossary he simply defines it as _magnes globosus_. Neither
_terrella_ nor _versorium_ appears in any Latin dictionary. No older writer
had used either word, though Peter Peregrinus (_De Magnete_, Augsburg,
1558) had described experiments with globular loadstones, and pivotted
magnetic needles suitable for use in a compass had been known for nearly
three centuries. Yet the pivotted needle was not denominated _versorium_.
Blondo (_De Ventis_, Venice, 1546) does not use the term. Norman (_The Newe
Attractiue_, London, 1581) speaks of the "needle or compasse," and of the
"wyre." Barlowe (_The Navigators Supply_, London, 1597) speaks of {2} the
"flie," or the "wier." The term _versorium_ (literally, the _turn-about_)
is Gilbert's own invention. It was at once adopted into the science, and
appears in the treatises of Cabeus, _Philosophia Magnetica_ (Ferrara,
1629), and of Kircher, _Magnes sive de Arte Magnetica_ (Coloniæ, 1643), and
other writers of the seventeenth century. Curiously enough, its adoption to
denote the pivotted magnetic needle led to the growth of an erroneous
suggestion that the mariners' compass was known to the ancients because of
the occurrence in the writings of Plautus of the term _versoriam_, or
_vorsoriam_. This appears twice as the accusative case of a feminine noun
_versoria_, or _vorsoria_, which was used to denote part of the gear of a
ship used in tacking-about. Forcellini defines _versoria_ as "funiculus quo
extremus veli angulus religatur"; while _versoriam capere_ is equivalent to
"reverti," or (metaphorically) "sententiam mutare." The two passages in
Plautus are:
EUT. Si huc item properes, ut istuc properas, facias rectius,
Huc secundus ventus nunc est; cape modo vorsoriam;
Hic Favonius serenu'st, istic Auster imbricus:
Hic facit tranquillitatem, iste omnes fluctus conciet.
(in _Mercat._ Act. V., sc. 2.)
CHARM. Stasime, fac te propere celerem recipe te ad dominum domum;
. . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . Cape vorsoriam
Recipe te ad herum.
(in _Trinum._ Act. IV., sc. 3.)
The word _magneticum_ is also of Gilbert's own coinage, as a noun; as an
adjective it had been certainly used before, at least in its English form,
_magneticall_, which appears on the title-page of William Borough's
_Discourse of the Variation of the Compasse_ (London, 1596). Gilbert does
not use anywhere the noun _magnetismus_, _magnetism_. The first use of that
noun occurs in William Barlowe's _Magneticall Aduertisements_ (1616), in
the _Epistle Dedicatorie_, wherein, when speaking of Dr. Gilbert, he says
"vnto whom I communicated what I had obserued of my selfe, and what I had
built vpon his foundation of the _Magnetisme_ of the earth." Gilbert speaks
of the _virtus magnetica_, or _vis magnetica_; indeed, he has a rich
vocabulary of terms, using, beside _virtus_ and _vis_, _vires_, _robur_,
_potestas_, _potentia_, _efficientia_, and _vigor_ for that which we should
now call _magnetism_ or _the magnetic forces_. Nor does he use the verb
_magnetisare_, or its participle, _magnetisatus_: he speaks of _ferrum
tactum_, or of _ferrum excitatum a magnete_. In spite of certain
obscurities which occur in places in his work, he certainly shows a nice
appreciation of words and their use, and a knowledge of style. One finds
occasionally direct quotations from, and overt references to, the classic
authors, as in the references to Plato and Aristotle on page 1, and in the
passage from the Georgics of Vergil on p. 21. But here and there one finds
other traces of unmistakable scholarship, as in the reference to goat's
wool on p. 35, or in the use, on p. 210, of the word _perplacet_, which
occurs in the letter of Cicero _ad Atticum_, or in that of _commonstrabit_,
occurring on p. 203, and found only in Cicero, Terence and Plautus; whilst
the phrase on p. 3, in which Gilbert rallies the smatterers on having lost
both their oil and their pains, has a delightfully classical echo. {3} The
term _orbis virtutis_, defined by Gilbert in the glossary, and illustrated
by the cuts on pages 76, 77, and 96, might be effectively translated by
_sphere of influence_, or _orbit within which there is sensible
attraction_. It has been preferred, however, to translate it literally as
the _orbe of virtue_, or _orbe of magnetick virtue_. This choice has been
determined by the desire to adopt such an English phrase as Gilbert would
himself have used had he been writing English. T. Hood, writing in 1592 in
his book _The Vse of both the Globes_, in using the word _orbe_, says that
the word _globe_ signifies a solid body, while a _sphere_ is hollow, like
two "dishes joyned by the brimme"; "The Latines properly call _Orbis_ an
Orbe"; "Moreouer the word _Sphaera_ signifieth that instrument made of
brasen hoopes (wee call it commonly a ringed Sphere) wherewith the
Astronomers deliuer unto the nouices of that Science the vnderstanding of
things which they imagine in the heauen." Further, Dr. Marke Ridley in his
_Treatise of Magneticall Bodies and Motions_ (1613), has a chapter (XIIII)
"Of the distance and Orbe of the Magnets vertue," throughout which the term
Orbe is retained. Sir Thomas Browne also writes of "the orb of their
activities."
The word _Coitio_, used by Gilbert for the mutual force between magnet and
iron, has been retained in its English form, _coition_. Gilbert evidently
adopted this term after much thought. The Newtonian conception of action
and reaction being necessarily equal had not dawned upon the mediæval
philosophers. The term _attraction_ had been used in a limited sense to
connote an action in which a force was conceived of as being exerted on one
side only. Diogenes of Apollonia, Alexander Aphrodiseus, Democritus, and
others, conceived the magnet to draw at the iron without the iron in any
way contributing to that action. Saint Basil specially affirms that the
magnet is not drawn by iron. On the other hand, Albertus Magnus had
conceived the idea that the iron sought the magnet by a one-sided effort in
which the magnet took no part. Gilbert had the wit to discern that the
action was mutual, and to mark the new conception he adopted the new term,
and defined it as it stands in his glossary. It is "a concourse or
concordancy of both," and to emphasize his meaning he adds, "not as if
there were an [Greek: helktikê dunamis] but a [Greek: sundromê]" not a
tractile power, but a running together. The adjective [Greek: helktikê] is
obviously related to the verb [Greek: helkô], I draw: but its meaning
puzzled the subsequent editors of the text, for in the two Stettin editions
of 1628 and 1633, the phrase appears in the respective forms of [Greek:
helêtikê dunamis] and [Greek: helkustikê dunamis]. In Creech's English
version of Lucretius (edition of 1722, p. 72a, in the footnote) is the
commentary "Galen, disputing against Epicurus, uses the term [Greek:
helkein], which seems likewise too violent." It may be noted that the same
verb occurs in the passage from the _Io_ of Plato quoted below. The term
[Greek: sundromê] applied by Gilbert to explain his term _Coitio_ is used
by Diodorus for the mutual onset of two hostile forces.
A picturesque sentence from Sir Thomas Browne's _Pseudodoxia Epidemica_
(London, 1650, p. 51) sets the matter succinctly forth. "If in two skiffs
of cork, a Loadstone and Steel be placed within the orb of their
activities, the one doth not move the other standing still, but both hoist
sayle and steer unto each other; so that if the Loadstone attract, the
Steel hath also its attraction; for in this action the Alliency is
reciprocall, which jointly felt, they mutually approach and run into each
others arms." {4} The page and line references given in these notes are in
all cases first to the Latin edition of 1600, and secondly to the English
edition of 1900.
[2] PAGE 1, LINE 28. Page 1, line 28. _Plato in Ione._--The passage in the
_Io_ of Plato is in chap. v. Socrates addressing the poet Io tells him that
his facility in reciting Homer is not really an art: [Greek: theia de
dunamis, hê se kinei hôsper en têi lithôi, hên Euripidês men Magnêtin
ônomasen, hoi de polloi Hêrakleian. kai gar autê hê lithos ou monon autous
tous daktulious agei tous sidêrous, alla kai dunamin entithêsi tois
daktuliois, ôst au dunasthai tautou touto poiein, hoper hê lithos, allous
agein daktulious, hôst' enioth' hormathos makros panu sidêriôn kai
daktuliôn ex allêlôn êrtêtai pasi de toutois ex ekeinês tês lithou hê
dunamis anêrtêtai.] The idea is that as the loadstone in attracting an iron
ring will make it into a magnet, which can in turn act magnetically on
another ring, and this on yet another, so the inspiration of the Muse is
transferred to the poet, who in turn hands on the inspiration through the
reciter to the listener. After further expanding the same idea of the
transference of influence, Socrates again mentions the magnet (chap. vii.):
[Greek: Oisth' oun hoti outos estin ho theatês tôn daktuliôn ho eschatos,
hôn egô elegon hupo tês Hêrakleiôtidos lithou ap' allêlôn tên dunamin
lambanein, ho de mesos su ho rhapsôdos kai hupokritês, ho de prôtos autos
ho poiêtês? ho de theos dia pantôn toutôn helkei tên psuchên hopoi an
boulêtai tôn anthrôpôn, k.t.l.] (Edition Didot of 1856, vol. i., p. 391; or
Stephanus, p. 533 D).
There is another reference in Plato to the magnet, namely, in the _Timæus_
(p. 240, vol. ii., Edit. citat.). See the Note to p. 61.
The reference by Euripides to the magnet occurs in the lost play of Oeneus,
in a fragment preserved by Suidas. See _Fragmenta Euripidis_ (Ed. Didot,
1846, p. 757, or Nauck's edition, No. 567).
[Greek: hôs Euripidês en Oinei; tas brotôn gnômas skopôn, hôste Magnêtis
lithos tên doxan helkei kai methistêsin palin.]
[3] PAGE 1, LINE 28. Page 1, line 29. The brief passage from Aristotle's
_De Anima_ referring to Thales is quoted by Gilbert himself at the bottom
of p. 11.
[4] PAGE 2, LINE 1. Page 1, line 29. The edition of 1628 inserts commas
between Theophrastus and Lesbius, and between Julius and Solinus, as though
these were four persons instead of two.
[5] PAGE 2, LINE 8. Page 2, line 5. _si allio magnes illitus fuerit, aut si
adamas fuerit_. An excellent version of this myth is to be found in Julius
Solinus, _Polyhistor, De Memorabilibus_, chap. lxiv., of which the English
version of 1587, by A. Golding, runs thus: "The Diamonde will not suffer
the Lodestone to drawe yron unto him: or if y^e Lodestone haue alreadie
drawne a peece of yron to it, the Diamond snatcheth and pulleth away as hys
bootye whatsoever the Lodestone hath taken hold of." Saint Augustine
repeats the diamond myth in his _De Civitate Dei_, lib. xxi. Baptista Porta
says (p. 211 of the English version of 1658): "It is a common Opinion
amongst Sea-men, That Onyons and Garlick are at odds with the Loadstone:
and Steers-men, and such as tend the Mariners Card are forbid to eat Onyons
or Garlick, lest they make the Index of the Poles drunk. But when I tried
all these things, found them to be false: for not onely breathing and
belching upon the Loadstone after eating of Garlick, did not stop its
vertues: but when it was all anoynted over with the juice of Garlick, it
did perform its office as well as if it had never been touched with it: and
I could observe almost not the least difference, lest I should make void
the endeavours of the Ancients. {5} And again, When I enquired of Marines,
whether it were so, that they were forbid to eat Onyons and Garlick for
that reason; they said, they were old Wives fables, and things ridiculous;
and that Sea-men would sooner lose their lives, then abstain from eating
Onyons and Garlick."
The fables respecting the antipathy of garlick and of the diamond to the
operation of the magnet, although already discredited by Ruellius and by
Porta, died hard. In spite of the exposure and denunciations of
Gilbert--compare p. 32--these tales were oft repeated during the succeeding
century. In the appendix to Sir Hugh Plat's _Jewel House of Art and
Nature_, in the edition of 1653, by D. B. Gent, it is stated there (p.
218): "The Loadstone which ... hath an admirable vertue not onely to draw
Iron to it self, but also to make any Iron upon which it is rubbed to draw
iron also, it is written notwithstanding, that being rubbed with the juyce
of Garlick, it loseth that vertue, and cannot then draw iron, as likewise
if a Diamond be layed close unto it."
Pliny wrote of the alleged antipathy between diamond and goat's blood. The
passage as quoted from the English version of Pliny's _Natural Historie of
the World_, translated by Philemon Holland (London, 1601, p. 610, chap,
iv.), runs: "But I would gladly know whose invention this might be to soake
the Diamond in Goats bloud, whose head devised it first, or rather by what
chance was it found out and knowne? What conjecture should lead a man to
make an experiment of such a singular and admirable secret, especially in a
goat, the filthiest beast ... in the whole world? Certes I must ascribe
both this invention and all such like to the might and beneficence together
of the divine powers: neither are we to argue and reason how and why Nature
hath done this or that? Sufficient is it that her will was so, and thus she
would have it."
[6] PAGE 2, LINE 22. Page 2, line 22. _Machometis sacellum._ Gilbert
credits Matthiolus (the well-known herbalist and commentator on
Dioscorides) with producing the fable as to Mahomet's coffin being
suspended in the air by a magnet. Sir Richard Burton, in his famous
pilgrimage to El Medïnah in 1855, effectually disposed of this myth. The
reputed sarcophagus rests simply on bricks on the floor. But it had long
been known that aerial suspension, even of the lightest iron object, in the
air, without contact above or below, was impossible by any magnetic agency.
In Barlowe's _Magneticall Aduertisements_ (London, 1616, p. 45) is the
following: "As for the Turkes _Mahomet_, hanging in the ayer with his yron
chest it is a most grosse untruth, and utterly impossible it is for any
thing to hange in the ayer by any _magneticall_ power, but that either it
must touch the stone it selfe, or else some intermediate body, that
hindreth it from comming to the stone (like as before I haue shewed) or
else some stay below to keepe it from ascending, as some small wier that
may scantly bee seene or perceived."
[7] PAGE 2, LINE 26. Page 2, line 26. _Arsinoes templum._--The account in
Pliny of the magnetic suspension of the statue of Arsinoe in the temple
built by Chinocrates is given as follows in the English version (London,
1601) of Philemon Holland (p. 515): "And here I cannot chuse but acquaint
you with the singular invention of that great architect and master deviser,
of Alexandria in Ægypt _Dinocrates_, who began to make the arched roufe of
the temple of _Arsinoe_ all of Magnet or this Loadstone, to the end, that
within that temple the statue of the said princesse made of yron, might
seeme to hang in the aire by nothing. But prevented he was by death {6}
before hee could finish his worke, like as king _Ptolomæe_ also, who
ordained that temple to be built in the honour of the said _Arsinoe_ his
sister."
There are a number of similar myths in Ausonius, Claudian, and Cassiodorus,
and in the writings of later ecclesiastical historians, such as Rusinus and
Prosper Aquitanus. The very meagre accounts they have left, and the
scattered references to the reputed magical powers of the loadstone,
suggest that there existed amongst the primitive religions of mankind a
_magnet-worship_, of which these records are traces.
[8] PAGE 2, LINE 37. Page 2, line 41. _Brasevolus_ [or _Brasavola_].--The
list of authorities here cited consists mostly of well-known mediæval
writers on _materia medica_ or on minerals: the last on the list, _Hannibal
Rosetius Calaber_, has not been identified.
The following are the references in the order named by Gilbert:
Antonio Musa Brasavola. _Examen omnium simplicium medicamentorum_, Section
447 (Lugdun., 1537).
Joannes Baptista Montanus. _Metaphrasis summaria eorum quæ ad
medicamentorum doctrinà attinet_ (Augustæ Rheticæ, 1551).
Amatus Lusitanus. _Amati Lusitani in Dioscoridis Anazarbei de materia
medica libros quinque_ (Venet., 1557, p. 507).
Oribasius. _Oribasii Sardiani ad Eunapium libri 4 quibus ... facultates
simplicium ... continentur_ (Venet., 1558).
Aetius Amidenus. _Aetii Amideni Librorum medicinalium ... libri octo nunc
primum in lucem editi_ (Greek text, Aldine edition, Venet., 1534). A Latin
edition appeared in Basel, 1535. See also his _tetrabiblos ex veteribus
medicinæ_ (Basil., 1542).
Avicenna (Ibn Sinâ). _Canona Medicinæ_ (Venice, 1486), liber ii., cap. 474.
Serapio Mauritanus (Yuhanná Ibn Sarapion). In hoc volumine continentur ...
_Ioan. Sarapionis Arabis de Simplicibus Medicinis opus præclarum et ingens
..._ (edited by Brunfels, Argentorati, 1531, p. 260).
Hali Abbas ('Alí Ibn Al 'Abb[=a]s). _Liber totius medicinæ necessaria
c[=o]tinens ... quem Haly filius Abbas edidit ... et a Stephano ex arabica
lingua reductus_ (Lugd., 1523, p. 176 _verso_).
Santes de Ardoniis (or Ardoynis). _Incipit liber de venenis quem magister
santes de ardoynis ... edere cepit venetiis die octauo nou[=e]bris_, 1424
(Venet., 1492).
Petrus Apponensis (or Petrus de Abano). The loadstone is referred to in two
works by this author.
(1) _Conciliator differentiarum philosophorum: et precipue medicorum
clarissimi viri Petri de Abano Patauini feliciter incipit_ (Venet., 1496,
p. 72, _verso_, Quæstio LI.).
(2) _Tractatus de Venenis_ (Roma, 1490, cap. xi.).
Marcellus (called Marcellus Empiricus). _De Medicamentis_, in the volume
_Medici antiqui omnes_ (Venet., 1547, p. 89).
Arnaldus (Arnaldus de Villa Nova). _Incipit Tractatus de virtutibus
herbarum_ (Venet., 1499). See also _Arnaldi Villanovani Opera omnia_
(Basil., 1585).
Marbodeus Gallus. _Marbodei Galli poetae vetustissimi de lapidibus
pretiosis Enchiridion_ (Friburgi, 1530 [1531], p. 41).
Albertus Magnus. _De Mineralibus et rebus metallicis_ (Venet., 1542, lib.
ii., _de lapidibus preciosis_, p. 192). There is a reference to the
loadstone {7} also in a work attributed falsely to Albertus, but now
ascribed to Henricus de Saxonia, _De virtutibus herbarum, de virtutibus
lapidum_, etc. (Rouen, 1500, and subsequent editions). An English version,
_The Secrets of Albertus Magnus of the vertues of hearbs stones and
certaine beasts_ was publisht in London in 1617.
Matthæus Silvaticus. _Pandectæ Medicinæ_ (Lugduni, 1541, cap. 446).
Hermolaus Barbarus. His work, _Hermolai Barbari Patritii Veneti et
Aqvileiensis patriarchæ Corollarii Libri quinque ..._ Venet., 1516, is an
early herbal. On p. 103 are to be found descriptions of _lapis gagatis_ and
_lapis magnes_. The latter is mostly taken from Pliny, and mentions the
alleged theamedes, and the myth of the floating statue.
Camillus Leonardus. _Speculum Lapidum_ (Venet., 1502, fol. xxxviii.). An
English translation, _The Mirror of Stones_, appeared in London in 1750.
Cornelius Agrippa. _Henrici Cor. Agrippæ ab Nettesheym ... De Occulta
Philosophia Libri Tres_ (Antv., 1531). The English version _Of the Vanitie
and uncertaintie of Artes_ was publisht in London, 1569, and again later.
Fallopius (Gabriellus). _G. F. de simplicibus medicamentis purgantibus
tractatus_ (Venet., 1566). See also his _Tractatus de compositione
medicamentorum_ (Venet., 1570).
Johannes Langius. _Epistolarum medicinalium volumen tripartitum_ (Paris,
1589, p. 792).
Cardinalis Cusanus (Nicolas Khrypffs, Cardinal de Cusa). _Nicolai Cusani de
staticis experimentis dialogus_ (Argentorati, 1550). The English edition,
entitled _The Idiot in four books_, is dated London, 1650.
[9] PAGE 3, LINE 1. Page 2, line 42. _Marcellus_.--"Marcellus Empiricus,
médecin de Théodose-le-Grand, dit que l'aimant, appelé _antiphyson_, attire
et repousse le fer." (Klaproth, _Sur l'invention de la boussole_, 1834, p.
12.) The passage from Marcellus runs: "Magnetes lapis, qui antiphyson
dicitur, qui ferrum trahit et abjicit, et magnetes lapis qui sanguinem
emittit et ferrum ad se trahit, collo alligati aut circa caput dolori
capitis medentur." (Marcellus, _de Medicamentis_: in the volume _Medici
antiqui omnes, qui latinis literis morborum genera persecuti sunt_. Venet.,
1547, p. 89.)
[10] PAGE 3, LINE 11. Page 3, line 9. _Thomas Erastus_.--The work in
question is _Dispvtationvm de Medicina nova Philippi Paracelsi, Pars Prima:
in qua quæ de remediis svperstitiosis & Magicis curationibus ille prodidit,
præcipuè examinantur à Thoma Erasto in Schola Heydebergensi, professore_.
(Basiliæ, 1572. Parts 2 and 3 appeared the same year, and Part 4 in 1573.)
Gilbert had no more love for Paracelsus than for Albertus Magnus or others
of the magic-mongers. Indeed the few passages in Paracelsus on the magnet
are sorry stuff. They will mostly be found in the seventh volume of his
collected works (_Opera omnia_, Frankfurt, 1603). A sample may be taken
from the English work publisht in London, 1650, with the title: _Of the
Nature of Things, Nine Books; written by Philipp Theophrastus of Hohenheim,
called Paracelsvs_.
"For any Loadstone that Mercury hath but touched, or which hath been
smeered with Mercuriall oyle, or only put into Mercury will never draw Iron
more" (p. 23).
"The life of the Loadstone is the spirit of Iron; which may bee extracted,
and taken away with spirit of Wine" (p. 32).
[11] PAGE 3, LINE 13. Page 3, line 11. _Encelius_ (or _Entzelt_, Christoph)
{8} wrote a work publisht in 1551 at Frankfurt, with the title _De re
metallica, hoc est, de origine, varietate, et natura corporum metallicorum,
lapidum, gemmarum, atque aliarum quæ ex fodinis eruuntur, rerum, ad
medicine usum deservientium, libri iii_. This is written in a singular
medley of Latin and German. Gilbert undoubtedly took from it many of his
ideas about the properties of metals. See the note to p. 27 on _plumbum
album_.
[12] PAGE 3, LINE 20. Page 3, line 21. _Thomas Aquinas._--The reference is
to his commentaries upon the _Physica_ of Aristotle. The passage will be
found on p. 96 _bis_ of the Giunta edition (Venet., 1539). The essential
part is quoted by Gilbert himself on p. 64.
[13] PAGE 3, LINE 39. Page 3, line 45. _pyxidem._--The word _pyxis_, which
occurs here, and in the next sentence as _pyxidem nauticam_, is translated
_compass_. Eleven lines lower occurs the term _nautica pyxidula_. This
latter word, literally the "little compass," certainly refers to the
portable compass used at sea. Compare several passages in Book IV. where a
contrasting use is made of these terms; for example, on pp. 177 and 202.
Calcagninus, _De re nautica_, uses the term _pyxidecula_ for an instrument
which he describes as "vitro intecta." On p. 152, line 9, Gilbert uses the
non-classical noun _compassus_, "boreale lilium compassi (quod Boream
respicit)," and again on p. 178, line 3.
[14] PAGE 4, LINE 2. Page 4, line 2. _Melphitani._--The inhabitants of
Amalfi in the kingdom of Naples. The claim of the discovery or invention of
the mariners' compass in the year 1302 by one Joannes Goia, or Gioia, also
named as Flavio Goia, has been much disputed. In Guthrie's _New System of
Modern Geography_ (London, 1792, p. 1036), in the Chronology, is set down
for the year 1302:
"The mariner's compass invented, or improved by Givia, of Naples. The
flower de luce, the arms of the Duke of Anjou, then King of Naples, was
placed by him at the point of the needle, in compliment to that prince."
In 1808 an elaborate treatise was printed at Naples, by Flaminius Venanson
with the title, _De l'invention de la Boussole Nautique_. Venanson, who
cites many authorities, endeavours to prove that if Gioia did not discover
magnetic polarity he at least invented the compass, that is to say, he
pivotted the magnetic needle and placed it in a box, with a card affixed
above it divided into sixteen parts bearing the names of the sixteen
principal winds. He alleges in proof that the compass-card is emblazoned in
the armorial bearings of the city of Amalfi. This view was combatted in the
famous letter of Klaproth to Humboldt publisht in Paris in 1834. He shows
that the use of the magnetized needle was known in Europe toward the end of
the twelfth century; that the Chinese knew of it and used it for finding
the way on land still earlier; that there is no compass-card in the arms of
the city of Amalfi; but he concedes that Gioia may have improved the
compass in 1302 by adding the wind-rose card. The most recent contributions
to the question are a pamphlet by Signorelli, _Sull' invenzione della
Bussola nautica, ragionamento di Pietro Napoli Signorelli, segretario
perpetuo della Società Pontaniana; letto nella seduta del 30 settembre
1860_; Matteo Camera's _Memorie Storico-diplomatiche dell' antica città e
ducato di Amalfi_ (Salerno, 1876); and Admiral Luigi Fincati's work _Il
Magnete, la Calamita, e la Bussola_ (Roma, 1878). An older mention of Gioia
is to be found in Blundevile's _Exercises_ (3rd edition, 1606, pp.
257-258). See also Crescentio _della Nautica Mediterranea_, (Roma, 1607, p.
253), and Azuni, _Dissertazione sull' origine della bussola nautica_
(Venezia, 1797). {9}
There appears to be a slip in Gilbert's reference to Andrea Doria, as he
has confounded the town of Amalfi in Principato Citra with Melfi in
Basilicata.
One of the sources relied upon by historians for ascribing this origin of
the compass is the _Compendia dell' Istoria del Regno di Napoli_, of
Collenuccio (Venet., MDXCI.), p. 5.
"Nè in questo tacerò Amalfi, picciola terra, & capo della costa di
Picentia, alia quale tutti quelli, che'l mar caualcano, vfficiosamente
eterno gratie debono referire, essendo prima in quella terra trovato l'vso,
& l'artificio della calamita, & del bussolo, col quale i nauiganti, la
stella Tramontana infallibilmente mirando, direzzano il lor corso, si come
è publica fama, & gli Amalfitani si gloriano, nè senza ragione dalli piu si
crede, essendo cosa certa, che gli antichi tale instromento non hebbero; nè
essendo mai in tutto falso quello, che in molto tempo è da molti si
diuolga."
Another account is to be found in the _Historiarum sui temporis_, etc., of
Paulus Jovius (Florent., 1552), tom. ii., cap. 25, p. 42.
"Quum essem apud Philippum superuenit Ioachinus Leuantius Ligur a Lotrechio
missus, qui deposceret captiuos; sed ille negauit se daturum, quando eos ad
ipsum Andream Auriam ammirantem deducendos esse iudicaret. Vgonis uerò
cadauer, ut illudentium Barbarorum contumeliis eriperetur, ad Amalphim
urbem delatum est, in ædeque Andreæ apostoli, tumultuariis exequiis
tumulatum. In hac urbe citriorum & medicorum odoratis nemoribus æquè
peramoena & celebri, Magnetis usum nauigantibus hodie familiarem &
necessarium, adinuentum suisse incolæ asserunt."
Flavius Blondus, whom Gilbert cites, gives the following reference, in
which Gioia's name is not mentioned, in the section upon Campania Felix of
his Italy (_Blondi Flavii Forlinensis ... Italia Illustrata_, Basiliæ,
1531, p. 420).
"Sed fama est qua Amalphitanos audiuimus gloriari, magnetis usum, cuius
adminiculo nauigantes ad arcton diriguntur, Amalphi suisse inuentum,
quicquid uero habeat in ea re ueritas, certû est id noctu nauigandi
auxilium priscis omnino suisse incognitum."
There is a further reference to the alleged Amalphian in Caelius
Calcagninus _De re nautica commentatio_. (_See Thesaurus Græcarum
Antiquitatum_, 1697, vol. xi., p. 761.) On the other hand Baptista Porta,
who wrote in Naples in 1558 (_Magia Naturalis_) distinctly sets aside the
claim as baseless.
William Barlowe, in _The Navigators Supply_ (1597, p. A3), says: "Who was
the first inuentor of this Instrument miraculous, and endued, as it were,
with life, can hardly be found. The lame tale of one _Flauius_ at
_Amelphis_, in the kingdome of _Naples_, for to haue deuised it, is of very
slender probabilitie. _Pandulph Collenutius_ writing the Neapolitane
historie telleth vs, that they of _Amelphis_ say, it is a common opinion
there, that it was first found out among them. But _Polidore Virgil_, who
searched most diligently for the Inuentors of things, could neuer heare of
this opinion (yet himselfe being an Italian) and as he confesseth in the
later ende of his third booke _de inventoribus rerum_, could neuer
vnderstand anything concerning the first inuention of this instrument."
According to Park Benjamin (_Intellectual Rise in Electricity_, p. 146) the
use of the pivotted compass arose and spread not from Amalfi at the hands
of Italians in the fourteenth century, but from Wisbuy, at the hands of the
Finns, in the middle of the twelfth century. {10}
Hakewill (_An Apologie or Declaration of the Power and Providence of God_,
London, 1673, pp. 284-285) says:
"But _Blondus_, who is therein followed by _Pancirollus_, both _Italians_,
will not haue _Italy_ loose the praise thereof, telling vs that about 300
yeares agoe it was found out at Malphis or Melphis, a Citty in the Kingdome
of _Naples_ in the _Province_ of _Campania_, now called _Terra di
Lovorador_. But for the Author of it, the one names him not, and the other
assures vs, he is not knowne: yet _Salmuth_ out of _Ciezus & Gomara_
confidently christens him with the name of _Flavius_, and so doth _Du
Bartas_ in those excellent verses of his touching this subject.
"'W' are not to _Ceres_ so much bound for bread,
Neither to _Bacchus_ for his clusters red,
As Signior _Flavio_ to thy witty tryall,
For first inventing of the Sea-mans dyall,
Th' vse of the needle turning in the same,
Divine device, O admirable frame!'
"It may well be then that _Flavius_ the _Melvitan_ was the first inventor
of guiding the ship by the turning of the needle to the _North_: but some
_German_ afterwards added to the _Compasse_ the 32 points of the winde in
his owne language, whence other Nations haue since borrowed it."
[15] PAGE 4, LINE 14. Page 4, line 14. _Paulum Venetum_.--The reference is
to Marco Polo. He returned in 1295 from his famous voyage to Cathay. But
the oft-repeated tale that he first introduced the knowledge of the compass
into Europe on his return is disposed of by several well-established facts.
Klaproth (_op. citat._, p. 57) adduces a mention of its use in 1240 in the
Eastern Mediterranean, recorded in a work written in 1242 by Bailak of
Kibdjak. And the passages in the Iceland Chronicle, and in Alexander of
Neckham are still earlier.
[16] PAGE 4, LINE 17. Page 4, line 17. _Goropius_. See _Hispanica Ioannis
Goropii Becani_ (Plantin edition, Antv., 1580), p. 29. This is a discussion
of the etymologies of the names of the points of the compass: but is quite
unauthoritative.
[17] PAGE 4, LINE 23. Page 4, line 26. _Paruaim_.--Respecting this
reference, Sir Philip Magnus has kindly furnisht the following note. A clue
to the meaning of _Parvaim_, which should be written in English letters
with a _v_, not a _u_, will be found in _2 Chronicles_, iii. 6. In the
verse quoted the author speaks of gold as the gold of Parvaim, [Hebrew:
WHAZAHAB ZHAB PARWAYIM], and [Hebrew: PRWYM] Parvaim is taken as a
gold-producing region. It is regarded by some as the same as Ophir. The
word is supposed to be cognate with a Sanskrit word _pûrva_ signifying
"prior, anterior, oriental." There is nothing in the root indicating gold.
A form similar to Parvaim, and also a proper name, is Sepharvaim, found in
_2 Kings_, xix. 13, and in _Isaiah_, xxxvii. 13, and supposed to be the
name of a city in Assyria.
[18] PAGE 4, LINE 35. Page 4, line 41. Cabot's observation of the variation
of the compass is narrated in the _Geografia_ of Livio Sanuto (Vinegia,
1588, lib. i., fol. 2). See also Fournier's _Hydrographie_, lib. xi., cap.
10.
[19] PAGE 4, LINE 36. Page 4, line 42. _Gonzalus Oviedus_.--The reference
is to Gonzalo Fernandez de Oviedo y Valdès. _Summario de la Historia
general y natural de las Indias occidentales_, 1525, p. 48, where the
author speaks of the crossing of "la linea del Diametro, donde las Agujas
hacen la {11} diferencia del Nordestear, ò Noroestear, que es el parage de
las Islas de los Açores."
[20] PAGE 5, LINE 8. Page 5, line 11. _Petri cujusdam Peregrini_.--This
opusculum is the famous letter of Peter Peregrinus written in 1269, of
which some twenty manuscript copies exist in various libraries in Oxford,
Rome, Paris, etc., and of which the oldest printed edition is that of 1558
(Augsburg). See also Libri, _Histoire des Sciences Mathématiques_ (1838);
Bertelli in Boncompagni's _Bull. d. Bibliogr._ T. I. and T. IV. (1868 and
1871), and Hellmann's _Rara Magnetica_ (1898). A summary of the contents of
Peregrinus's book will be found in Park Benjamin's _Intellectual Rise in
Electricity_ (1895), pp. 164-185.
[21] PAGE 5, LINE 12. Page 5, line 15. _Johannes Taisner
Hannonius._--Taisnier, or Taysnier, of Hainault, was a plagiarist who took
most of the treatise of Peregrinus and publisht it in his _Opusculum... de
Natura Magnetis_ (Coloniæ, 1562), of which an English translation by
Richard Eden was printed by R. Jugge in 1579.
[22] PAGE 5, LINE 18. Page 5, line 23. _Collegium Conimbricense_.--This is
a reference to the commentaries on Aristotle by the Jesuits of Coimbra. The
work is _Colegio de Coimbra da Companhia de Jesu, Cursus Conimbricensis in
Octo libros Physicorum_ (Coloniæ, sumptibus Lazari Ratzneri, 1599). Other
editions: Lugd. 1594; and Colon., 1596. The later edition of 1609, in the
British Museum, has the title _Commentariorum Collegii Conimbricensis in
octo libros physicorum_.
[23] PAGE 5, LINE 25. Page 5, line 31. _Martinus Cortesius_.--His _Arte de
Navegar_ (Sevilla, 1556) went through various editions in Spanish, Italian,
and English. Eden's translation was publisht 1561, and again in 1609.
[24] PAGE 5, LINE 26. Page 5, line 33. _Bessardus_.--Toussaincte de Bessard
wrote a treatise, _Dialogue de la Longitude_ (Rouen, 1574), which gives
some useful notes of nautical practice, and of the French construction of
the compass. Speaking of the needle he says: "Elle ne tire pas au pole du
monde: ains regarde, au Pole du Zodiaque, comme il sera discoursu, cy
apres" (p. 34). On p. 50 he speaks of "l'aiguille Aymantine." On p. 108 he
refers to Mercator's _Carte Générale_, and denies the existence of the
alleged loadstone rock. On p. 15 he gives the most naïve etymologies for
the terms used: thus he assigns as the derivation of _Sud_ the Latin
_sudor_, because the south is hot, and as that of _Ouest_ that it comes
from _Ou_ and _Est_. "Come, qui diroit, Ou est-il? à scauoir le Soleil, qui
estoit nagueres sur la terre."
[25] PAGE 5, LINE 28. Page 5, line 35. _Jacobus Severtius_.--Jacques
Severt, whose work, _De Orbis Catoptrici sev mapparvm mvndi principiis
descriptione ac usu libri tres_ (Paris, 1598), would have probably lapsed
into obscurity, but being just newly publisht was mentioned by Gilbert for
its follies.
[26] PAGE 5, LINE 30. Page 5, line 38. _Robertus Norman_.--Author of the
rare volume _The Newe Attractiue_, publisht in London, 1581, and several
times reprinted. This work contains an account of Norman's discovery of the
Dip of the magnetic needle, and of his investigation of it by means of the
Dipping-needle, which he invented. He was a compassmaker of the port of
London, and lived at Limehouse.
[27] PAGE 5, LINE 32. Page 5, line 40. _Franciscus Maurolycus_.--The work
to which the myth of the magnetic mountains is thus credited is, _D.
Francisci Abbatis Messanensis Opuscula Mathematica_, etc. (Venet, MDLXXV,
p. 122a). "Sed cur sagitta, vel obelus à vero Septentrione, quandoque ad
dextram, {12} quandoque ad sinistram declinat? An quia sagitta, sicut
magnes (cuius est simia) non verum Septentrionem, sed insulam quandam (quam
Olaus Magnus Gothus in sua geographia vocat insulam magnetum) semper ex
natura inspicere cogitur?"
[28] PAGE 5, LINE 35. Page 5, line 43. _Olaus Magnus_.--The famous
Archbishop of Upsala, who wrote the history of the northern nations
(_Historia de Gentibus Septentrionalibus_), of which the best edition,
illustrated with many woodcuts, appeared in Rome in 1555. An English
edition entitled _A Compendious History of the Goths, Swedes, and Vandals,
and Other Northern Nations_ was printed in London in 1658; but it is much
abbreviated and has none of the quaint woodcuts. The reference on p. 5
appears to be to the following passage on p. 409 (ed. 1555). "Demum in
suppolaribus insulis magnetum montes reperiuntur, quorum fragmentis ligna
fagina certo tempore applicata, in saxeam duritiem, et vim attractivam
convertuntur," or the following on p. 89: "Magnetes enim in extremo
Septentrionis veluti montes, unde nautica directio constat, reperiuntur:
quorum etiam magnetum tam vehemens est operatio, ut certis lignis fagineis
conjuncti, ea vertunt in sui duritiem, & naturam attractivam." On p. 343 is
a woodcut depicting the penalties inflicted by the naval laws upon any one
who should maliciously tamper with the compass or the loadstone, "qui
malitiosè nauticum gnomonem, aut compassum, & præcipuè portionem magnetis,
unde omnium directio dependet, falsaverit." He was to be pinned to the mast
by a dagger thrust through his hand. It will be noted that the ships
carried both a compass, and a piece of loadstone wherewith to stroke the
needle.
There is in the Basel edition of this work, 1567, a note _ad lectorem_, on
the margin of Carta 16a, as follows:
"Insula 30 milliarium in longitud. & latitud. Polo arctico subjecta.
"Vltra quam directorium nauticum bossolo dic[~u] uires amittit: propterea
quòd ilia insula plena est magnetum."
This myth of the magnetic mountains, probably originating with Nicander,
appears, possibly from an independent source, in the East, in China, and in
the tales of the Arabian Nights.
Ptolemy gives the following account in his _Geographia_ (lib. vii., cap.
2):
[Greek: Pherontai de kai allai sunecheis deka nêsoi kaloumenai Maniolai en
ais phasi ta sidêrous echonta hêlous ploia katechesthai, mêpote tês
Hêrikleias lithou peri autas genomenês, kai dia touto epiourois
naupêgeisthai.] Some editions omit the name of the Manioles from the
passage.
No two authorities agree as to the place of these alleged magnetic
mountains. Some place them in the Red Sea. Fracastorio, _De Sympathia et
Antipathia_, cap. 7 (_Opera omnia_, Giunta edition, 1574, p. 63), gives the
following reason for the variation of the compass:
"Nos igitur diligentius rem considerãtes dicimus causam, [~q] perpendiculum
illud ad polum vertatur, esse montes ferri, & magnetis, qui sub polo sunt,
vt negociatores affirmant, quorum species per incredibilem distantiam vsque
ad maria nostra propagata ad perpendiculum vsq;, vbi est magnes, consuetam
attractionem facit: propter distantiam autem quum debilis sit, non moueret
quidem magnetem, nisi esset in perpendiculo: quare & si non trahit vsq; ac.
principium, vnde effluxit, at mouet tam[~e], & propinquiorem facit, quo
potest. Quod si naues sorte vllæ propinquiores sint illis montibus, ferrum
omne ear[~u] cuellitur, propter quod nauigijs incolæ vtuntur clauis ligneis
astrictis."
In the last chapter of his _De Sympathia_, Fracastorio returns to the
subject {13} in consequence of some doubts expressed by Giambattista
Rhamnusio, seeing that the loadstones in the Island of Elba do not sensibly
deflect the magnet. Fracastorio replies thus (p. 76, _op. citat._):
"Primum igitur vtrum sub Polo sint. Magnetis mõtes, nec ne, sub ambiguo
relinquamus, scimus enim esse, qui scribãt planas magis esse eas regiones,
de quo Paulus Iouius E[~p]us Nucerinus Lucul[~e]tus historiar[~u] nostri
t[~e]poris scriptor, circa eã Sarmatiæ partem, quæ Moscouia n[~u]c dicitur,
diligent[~e] inquisitionem ab incolis fecit, qui ne eos etiã inueniri
montes retulere, qui Rhyphei ab antiquis dicti sunt: meminimus tam[~e] nos
quasdam chartas vidisse earum, quas mundi mappas appellãt, in quibus sub
polo montes notati erant (qui Magnetis montes inscripti fuerant). Siue
igitur sint, siue non sint ij montes, nihil ad nos in præsentiarum attinet,
quando per montes polo subiectos cathenam illam montium intelligimus, qui
ad septentrionem spectant tanti, & tam vasti, ac Ferri & Magnetis feraces:
qui, & si magis distant à nostro mari, [~q] Iluæ insulæ montes, potentiores
tamen sunt ad mouendum perpendiculum propter abundantiam & copiã Ferri, &
Magnetis. Fortasse autem, & qui in Ilua est Magnes, non multæ actionis est
in ea minera: multi enim d[~u] in minera sunt, minus valent, [~q] extracti,
[~q] spirituales species sua habeant impedimenta: signum autem parum valere
in sua minera Iluæ insulæ Magnetem, [~q] tam propinquus quum sit nauigijs
illac prætereuntibus, perpendiculum tamen non ad se cõuertit."
Aldrovandi in the _Musæum Metallicum_ (Bonon., 1648, p. 554) gives another
version of the fable:
"Nonnulli, animadversa hac Magnetis natura, scripserunt naves, quibus in
Calecutanam regionem navigatur, clavis ferreis non figi, ob magneticorum
frequentiam scopulorum, quoniam facilè dissolverentur. Sed Garzias in
Historia Aromatum id fabulosum esse tradidit: quandoquidem plures naues
Calecutanæ regionis, & illius tractus, ferreis clauis iunctas obseruauit:
immò addidit naues in insulis Maldiuis ligneis quidem clauis copulari, non
quia à Magnete sibi metuant, sed quoniam ferri inopia laborant."
According to Aldrovandi (p. 563, _op. citat._) the magnetic mountains are
stated by Sir John Mandeville to be in the region of Pontus.
Lipenius in his _Navigatio Salomonis Ophritica illustrata_ (Witteb., 1660),
which is a mine of curious learning, in discussing the magnetic mountains
quotes the reply of Socrates to the inquirer who asked him as to what went
on in the infernal regions, saying that he had never been there nor had he
ever met any one who had returned thence.
The loadstone rock figures in several early charts. In Nordenskiöld's
_Facsimile Atlas_ (Stockholm, 1889) is given a copy of the Map of Johan
Ruysch from an edition of Ptolemy, publisht in Rome in 1508, which shows
four islands within the ice-bound Arctic regions. South of these islands
and at the east of the coast of Greenland is the inscription: _Hic
compassus navium non tenet, nec naves quæ ferrum tenent revertere valent._
To which (on p. 63) Nordenskiöld adds the comment: _Sagan on magnetberg,
som skulle draga till sig fartyg förande jern, är gamal._ And he recalls
the reference of Ptolemy to the magnetic rocks in the Manioles. A second
inscription is added to Ruysch's map in the ornamental margin that borders
the Arctic islands. _Legere est in libro de inventione fortunati sub polo
arctico rupem esse excelsam ex lapide magnete 33 miliarium germanorum
ambitu._ This refers to a matter recorded in Hakluyt's _Principall
Navigations_ (Lond., 1589, p. 249), namely: "A Testimonie of the learned
Mathematician, maister John Dee, {14} touching the foresaid voyage of
Nicholas de Linna. Anno 1360 a frier of Oxford, being a good Astronomer,
went in companie with others to the most Northren islands of the world, and
there leaving his company together, he travelled alone, and purposely
described all the Northern islands, with the indrawing seas: and the record
thereof at his return he delivered to the king of England. The name of
which booke is _Inventio Fortunata_ (_aliter fortunæ_) _qui liber incipit a
gradu 54 usq. ad polum_."
The situation of the alleged loadstone rock is thus described by T.
Blundevile in his _Exercises_ in the chapter entitled _A plaine and full
description of Peter Plancius his vniuersall Map, seruing both for sea and
land, and by him lately put foorth in the yeare of our Lord, 1592_....
Written in our mother tongue by M. Blundeuill, Anno Domini 1594. The
passage is quoted from p. 253 of the third edition (1606):
"Now betwixt the 72. and 86. degrees of North latitude he setteth downe two
long Ilands extending from the West towardes the East somewhat beyond the
first Meridian, and from the saide Meridian more Eastward he setteth downe
other two long Ilandes ... and hee saith further that right under the North
pole there is a certaine blacke and most high rocke which hath in circuite
thirtie and three leagues, which is nintie and nine miles, and that the
long Iland next to the Pole on the West is the best and most healthfull of
all the North parts. Next to the foresaide Ilandes more Southward hee
setteth downe the Ilandes of Crocklande and Groynelande, making them to
haue a farre longer and more slender shape then all other mappes doe....
Moreouer at the East end of the last Ilande somewhat to the Southwarde, he
placeth the Pole of the Lodestone which is called in Latine Magnes, euen as
Mercator doth in his Mappe who supposing the first Meridian to passe
through Saint Marie or Saint Michael, which are two of the outermost
Ilandes of the Azores Eastwarde, placeth the Pole of the stone in the
seuentie fiue degree of Latitude, but supposing the first Meridian to passe
through the Ile Coruo, which is the furthest Ile of the Azores Westwarde,
he placeth the Pole of the Lodestone in the seuentie seuen degree of
Latitude."
Further, in the chapter on _The Arte of Nauigation_ in the same work (p.
332, _ed. citat._), Blundevile says:
"But whereas Mercator affirmeth that there should bee a mine or great rocke
of Adamant, wherunto all other lesser rockes or Needles touched with the
Lodestone doe incline as to their chiefe fountaine, that opinion seemeth to
mee verie straunge, for truely I rather beleeue with Robert Norman that the
properties of the Stone, as well in drawing steele, as in shewing the North
Pole, are secret vertues given of GOD to that stone for mans necessarie vse
and behoofe, of which secrete vertues no man is able to shewe the true
cause."
The following is one of the inscriptions in the compartments of the great
Chart of Mercator entitled _Ad Usum Navigantium_, published in 1569:
"Testatur Franciscus Diepanus peritissimus nauarchus volubiles libellas,
magnetis virtute infectas recta mundi polum respicere in insulis C.
Viridis, Solis, Bonauista, et Maio, cui proxime astipulantur qui in
Tercera, aut S. Maria (insulæ sunt inter Açores) id fieri dicunt, pauci in
earundem occidentalissima Corvi nomine id contingere opinantur. Quia vero
locorum longitudinis a communi magnetis et mundi meridiano iustis de causis
initium sumere oportet, plurium testimonium sequutus primum meridianum per
dictas C. Viridis insulas protraxi, et quum alibi plus minusque a polo
deuiante {15} magnete polum aliquum peculiarem esse oporteat quo magnetes
ex omni mundi parte despiciant, euum hoc quo assignaui loco existere
adhibita declinatione magnetis Ratisbonæ obseruata didici. Supputaui autem
eius poli situm etiam respectu insulæ Corui, ut iuxta extremo primi
meridiani positus extremi etiam termini, intra quos polum hunc inueniri
necesse est, conspicui fierent, donec certius aliquod nauclerorum
obseruatio attulerit."
Not all the map-makers were as frank as Paulus Merula, the author of a
_Cosmographia Generalis_, printed by Plantin in 1605, at Leyden. For in the
description of his _tabula universalis_ (_op. citat._ lib. iii., cap. 9) he
says that he does not believe in the magnetic islands; but that he has put
them into his chart lest unskilful folk should think that he had been so
careless as to leave them out!
In the well-known myth of Ogier the Dane, immortalized by William Morris in
the _Earthly Paradise_ (London, 1869, vol. i., p. 625), the loadstone rock
is an island in the far North. But this story is not one of the
Scandinavian sagas, and belongs to the Carlovingian cycle of heroic poems,
of which the chief is the _Chanson de Roland_; and Ogier le Danois is
really not a Dane but an _Ardennois_.
In the Middle-High German epic of Kudrun, the adventures of the fleet of
Queen Hilda when attracted by the loadstone mountain at Givers, in the
North Sea, are narrated at some length. (See _Kudrun, herausgegeben und
erklärt von Ernst Martin_. Halle, 1872.) One stanza will serve as a sample:
1126. Ze Givers vor dem berge | lac daz Hilden her.
swie guot ir anker wæren, | an daz vinster mer.
magnêten die steine | heten si gezogen.
ir guote segelboume | stuonden alle gebogen.
which may be rendered:
1126. At Givers before the mountain | lay Hilda's ships by.
Though good their anchors were, | upon the murky sea.
Magnets the stones were | had drawn them thither.
Their good sailing masts | stood all bent together.
Recent magnetic research has shown that while there are no magnetic
mountains that would account for the declination of the compass in general,
yet there are minor local variations that can only be accounted for by the
presence of magnetic reefs or rocks. The reader is referred to the account
of the magnetic survey of Great Britain in the _Philosophical Transactions_
(1890) by Professors Rücker and Thorpe. The well-known rocky peak the
Riffelhorn above Zermatt, in Switzerland, produces distinct perturbations
in the direction of the compass within half a mile of its base. Such local
perturbations are regularly used in Sweden for tracing out the position of
underground lodes of iron ore. See Thalén, _Sur la Recherche des Mines de
Fer à l'aide de Mesures magnétiques_ (Soc. Royale des Sciences d'Upsal,
1877); or B. R. Brough, _The Use of the Magnetic Needle in exploring for
Iron Ore_ (_Scientific American_, Suppl. No. 608, p. 9708, Aug. 27, 1887).
Quite recently Dr. Henry Wilde, F.R.S., has endeavoured to elucidate the
deviations of the compass as the result of the configurations of land and
sea on the globe, by means of a model globe in which the ocean areas are
covered with thin sheet iron. This apparatus Dr. Wilde calls a
_Magnetarium_. See _Proc. Roy. Soc._, June, 1890, Jan., 1891, and June,
1891. {16} An actual magnetic rock exists in Scandinavia, the following
account of it being given in the _Electrical Review_ of New York, May 3,
1899:
"The island of Bornholm in the Baltic, which consists of a mass of magnetic
iron ore, is much feared by mariners. On being sighted they discontinue
steering by compass, and go instead by lighthouses. Between Bornholm and
the mainland there is also a dangerous bank of rock under water. It is said
that the magnetic influence of this ore bank is so powerful that a balanced
magnetic needle suspended freely in a boat over the bank will take a
vertical position."
[29] PAGE 5, LINE 35. Page 5, line 43. _Josephus Costa._--This is
unquestionably a misprint for _Acosta_ (Joseph de), the Jesuit, whose work
_Historia natural y moral de las Indias_ was publisht at Seville in 1590.
An Italian edition appeared at Venice in 1596. The English edition,
translated by E. Grimestone, _The Naturall and Morall Historie of the East
and West Indies_, was publisht in London in 1604 and 1878. There are in
Gilbert's book references to two writers of the name of Costa or Costæus,
Joannes Costa of Lodi, who edited Galen and Avicenna (see pp. 3 and 62),
and Filippo Costa of Mantua, who wrote on antidotes and medicaments (see p.
141). The passage to which Gilbert refers is in Acosta's _Historia_ (ed.
1590, p. 64).
"Deziame a mi vn piloto muy diestro Portugues [~q] eran quatro puntos en
todo el orbe, donde se afixaua el aguja con el Norte, y contaualas por sus
nombres, de que no me acuerdo bien. Vno destos es el paraje de la Isla del
Cueruo, en las Terceras, o Islas de Açores, como es cosa y a muy sabida.
Passando di alli a mas altura, Noruestea, que es dezir, [~q] declina al
Poniente ... que me digã la causa desta efecto?... Porque vn poco de hierro
de fregarse cõ la piedra Iman ...
"Mejor es, como dize Gregorio Theologo, que a la Fe se sujete la razon,
pues aun en su casa no sabe bien entenderse...."
[30] PAGE 5, LINE 36. Page 5, line 45. _Livius Sanutus._--Livio Sanuto
publisht at Venice in 1588 a folio work, _Geografia distinta in xii Libri;
ne' quali, oltre l'esplicatione di nostri luoghi di Tolomeo, della Bussola
e dell' Aguglia, si dichiarono le provincie ... dell' Africa_. In this work
all Liber i. (pages 1-13) deals with observations of the compass,
mentioning Sebastian Cabot, and other navigators. He gives a map of Africa,
showing the central lakes out of which flow the _Zaires fluvius_ and the
_Zanberes fluvius_.
[31] PAGE 6, LINE 2. Page 6, line 5. _Fortunius Affaitatus._--The work of
Affaytatus, _Physicæ ac astronomiæ considerationes_, was publisht in Venice
in 1549.
[32] PAGE 6, LINE 3. Page 6, line 6. _Baptista Porta._--The reference is to
his celebrated _Magia naturalis_, the first edition of which came out in
1558 at Naples. An English edition, _Natural Magick by John Baptista Porta,
a Neapolitaine_, was printed in London, 1658. Book seven of this volume
treats "Of the wonders of the Load-stone." In the proem to this book Porta
says: "I knew at Venice R. M. Paulus, the Venetian, that was busied in the
same study: he was Provincial of the Order of servants, but now a most
worthy Advocate, from whom I not only confess, that I gained something, but
I glory in it, because of all the men I ever saw, I never saw any man more
learned, or more ingenious, having obtained the whole body of learning; and
is not only the Splendor and Ornament of Venice or Italy, but of the whole
world." The reference is to Fra Paolo Sarpi, better known as the historian
of the Council of Trent. Sarpi was himself known to Gilbert. {17}
His relations with Gilbert are set forth in the memoir prefixt to the
edition of his works, _Opere di Fra Paolo Sarpi, Servita_ ... in Helmstat,
MDCCLXI, p. 83. "Fino a questi giorni continuava il Sarpi a raccorre
osservazioni sulla declinazione dell' Ago Calamitato; e poi ch' egli,
atteso il variare di tal declinazione, assurdità alcuna non trovava
riguardo al pensamento dell' Inglese Guglielmo Gilberto, cioè, che
l'interno del nostro Globo fosse gran Calamita...." Here follows a
quotation from a letter of Sarpi to Lescasserio:
"... Unde cuspidem trahi a tanta mole terrena, quæ supereminet non absurde
putavit Gullielmus Gilbertus, et in eo meridiano respicere recta polum,
cave putes observatorem errasse. Est Vir accuratissimus, et interfuit
omnibus observationibus, quas plures olim fecimus, et aliquas in sui
gratiam, et cum arcubus vertici cupreo innitentibus, et cum innatantibus
aquæ, et cum brevibus, et cum longis, quibus modis omnibus et Hierapoli
usus suit."
Sarpi had correspondence with Gilbert, Bacon, Grotius, and Casaubon. He
also wrote on magnetism and other topics _in materia di Fisica_, but these
writings have perisht. He appears to have been the first to recognize that
fire destroyed the magnetic properties. (See _Fra Paolo Sarpi, the greatest
of the Venetians_ by the Rev. Alexander Robertson, London, 1894; see also
the notice of Sarpi in Park Benjamin's _Intellectual Rise in Electricity_.)
[33] PAGE 6, LINE 7. Page 6, line 11.: _R. M. Paulus Venetus_. See
preceding note.
[34] PAGE 6, LINE 21. Page 6, line 28.: _Franciscus Rueus_.--Francois de la
Rue, author of _De Gemmis Aliquot_ ... (Paris, 1547). Amongst other fables
narrated by Rueus is that if a magnet is hung on a balance, when a piece of
iron is attracted and adheres to the magnet, it adds nothing to the weight!
[35] PAGE 6, LINE 25. Page 6, line 33.: _Serapio_.--This account of the
magnetic mountains will be found in an early pharmacology printed in 1531
(Argentorati, G. Ulricher Andlenus), with the title "In hoc volumine
continetur insignium medicorum Joan. Serapionis Arabis de Simplicibus
Medicinis opus præclarum et ingens, Averrois Arabis de eisdem liber
eximius, Rasis filius Zachariæ de eisdem opusculum perutile." It was edited
by Otho Brunsels. Achilles P. Gasser, in his Appendix to the Augsburg
edition of Peregrinus, gives a reference to Serapio Mauritanus, parte 2,
cap. 394, libri _de medicinis compositis._
[36] PAGE 6, LINE 30. Page 6, line 39.: _Olaus Magnus_. See note to p. 5.
[37] PAGE 6, LINE 34. Page 6, line 44.: _Hali Abas_.--A reference is given
in Gasser's (1558) edition of Peregrinus to Haliabbas Arabs, lib. 2,
_practicæ_ cap. 45, _Regalis Dispositionis Medicinæ_. The passage to which
Gilbert refers is found in the volume _Liber totius medicinæ necessaria
c[=o]tinens ... quem Haly filius Abbas ... edidit ... et a Stephano ex
arabica lingua reductus_. (Lugd., 1523, 4to.) Liber Primus. Practice, Cap
xlv. _de speciebus lapidum_, § 466. "Lapis magnetes filis e [=v]tute
sadenego: & aiunt q[=m] si teneat^r in manu mitigat [=q] sunt in pedib^s
ipis dolores ac spasm[=u]."
Mr. A. G. Ellis identifies the noun _sadenegum_ as a Latin corruption of
the Arabic name of hæmatite, _shâdanaj_.
[38] PAGE 6, LINE 36. Page 6, line 46.: _Pictorius_.--His poem was publisht
at Basel, 1567. See also note on Marbodæus, p. 7, line 20, below.
[39] PAGE 6, LINE 36. Page 7, line 1.: _Albertus Magnus_.--Albertus, the
celebrated Archbishop of Ratisbon, is responsible for propagating sundry of
the myths of the magnet; and Gilbert never loses a chance of girding at
him. {18} The following examples are taken from the treatise _De
mineralibus et rebus metallicis_ (Liber II. _de lapidibus preciosis_),
Venet., 1542.
p. 171. "Et quod mirabile videtur multis his lapis [adamas] quando Magneti
supponitur ligat Magnetem et non permittit ipsum ferrum trahere."
p. 193. "Vnctus aut[~e] lapis alleo non trahit, si superponitur ei Adamas
iterum non attrahit, ita quod paruus Adamas magn[~u] ligat Magnet[~e].
Inventus aut[~e] est nostris t[~e]poribus Magnes qui ab uno angulo traxit
ferr[~u] et ab alio fugavit, et hunc Aristot. ponit aliud genus esse
Magnetis. Narrauit mihi quidam ex nostris sociis experim[~e]tator quod
uidit Federicum Imperatorem habere Magnetem qui non traxit ferrum, sed
ferrum uiceuersa traxit lapidem."
The first edition of this work _de mineralibus_ appears to have been
publisht in Venice as a folio in 1495.
[40] PAGE 7, LINE 9. Page 7, line 15. _Gaudentius Merula_.--This obscure
passage is from Liber IIII., cap. xxi., _Lapides_, of the work
_Memorabilium Gaudentii Merulæ..._ (Lugd., 1556), where we find:
"Qui magneti vrsæ sculpserit imaginem, quãdo Luna melius illuc aspiciat, &
filo ferreo susp[~e]derit, compos fiet vrsæ cælestis virtutis: verùm cum
Saturni radiis vegetetur, satius fuerit eam imaginem non habere: scribunt
enim Platonici malos dæmones septentrionales esse" (p. 287).
"Trahit autem magnes ferrum ad se, quod ferro sit ordine superior apud
vrsum" (p. 287).
The almost equally obscure passage in the _De triplici vita_ of Marsiglio
Ficino (Basil., 1532) runs:
"Videmus in specula nautarum indice poli libratum acum affectum in
extremitate Magnete moueri ad Vrsam, illuc uidelicet trahente Magnete:
quoniam & in lapide hoc præualet uirtus Vrsæ, & hinc transfertur in ferrum,
& ad Vrsam trahit utrunq;. Virtus autem eiusmodi tum ab initio infusa est,
tum continue Vrsæ radijs uegetatur, Forsitan ita se habet Succinum ad polum
alterum & ad paleas. Sed dic interea, Cur Magnes trahit ubiq; ferrum? non
quia simile, alioquin & Magnetem Magnes traheret multo magis, ferrum[=q];
ferr[=u]: non quia superior in ordine corporum, imò superius est lapillo
metallum ... Ego autem quum hæc explorata hactenus habuissem admodum
gratulabar, cogitabam[=q]; iuuenis adhuc Magneti pro uiribus inscluperet
(_sic_) coelestis Vrsæ figuram, quando Luna melius illuc aspiciat, & ferro
t[=u]c filo collo suspendere. Sperabam equidem ita demum uirtutis me
sideris illius compotem fore," &c. (p. 172).
[41] PAGE 7, LINE 14. Page 7, line 20. _Ruellius_.--Joannes Ruellius wrote
a herbal _De Natura Stirpium_, Paris, 1536, which contains a very full
account of amber, and a notice of the magnet (p. 125) and of the fable
about garlic. But on p. 530 of the same work he ridicules Plutarch for
recording this very matter.
[42] PAGE 7, LINE 20. Page 7, line 27. _Marbodæus Gallus_.--This rare
little book is entitled _Marbodei Galli Poetæ vetustissimi de lapidibus
pretiosis Enchiridion_. It was printed at Paris in 1531. The Freiburg
edition, also of 1531, has the commentaries of Pictorius. The poem is in
Latin hexameters. After a preface of twenty-one lines the virtues of stones
are dealt with, the paragraph beginning with a statement that Evax, king of
the Arabs, is said to have written to Nero an account of the species, names
and colours of stones, their place of origin and their potencies; and that
this work formed the basis of the poem. The alleged magical powers of the
magnet are recited in Caput I., _Adamas_. Caput XLIII., _Magnes_, gives
further myths. {19} The commentary of Pictorius gives references to earlier
writers, Pliny, Dioscorides, Bartholomæus Anglicus, Solinus, Serapio, and
to the book _de lapidibus_ erroneously ascribed to Aristotle.
The following is a specimen of the poem of Marbodeus:
_Magnetes lapis est inuentus apud Trogloditas,_
_Qu[=e] lapid[=a] genetrix nihilominus India mittit._
_Hic ferruginei cognoscitur esse coloris,_
_Et ui naturæ uicinum tollere ferrum._
_Ededon magus hoc primum ferè dic[=i]tur usus,_
_Conscius in magica nihil esse potentius arte._
_Post illum fertur famosa uenefica Circe_
_Hoc in præstigijs magicis specialiter usa._
This poem was reprinted (1854) in Migne's _Patrologia_. In 1799 Johann
Beckmann issued an annotated variorum edition of Marbodeus (_Marbodi Liber
Lapidvm sev de Gemmis_..., Göttingæ, 1799), in which there is a
bibliography of the poem, the first edition of which appears to have been
publisht in 1511, at Vienna, thirteen other editions being described.
Beckmann adds many illustrative notes, and a notice of the Arabian Evax,
who is supposed to have written the treatise _de lapidibus_. Not the least
curious part is a French translation alleged to have been written in 1096,
of which Chap. XIX. on the Magnet begins thus:
Magnete trovent Trogodite,
En Inde e precieus est ditte.
Fer resemble e si le trait,
Altresi cum laimant fait.
Dendor lama mult durement.
Qi lusoit a enchantement.
Circe lus a dot mult chere,
Cele merveillose forciere, &c.
[43] PAGE 7, LINE 21. Page 7, line 28. _echeneidis._--The _echeneis_, or
sucking-fish, reputed to have magical or magnetic powers, is mentioned by
many writers. As an example, see Fracastorio, _De Sympathia et Antipathia_,
lib. i., cap. 8, _De Echineide, quomodo firmare nauigia possit_ (Giunta
edition, Venet., 1574, p. 63). For other references to the _Echeneis_ see
Gaudentius Merula (_op. citat._) p. 209. Also Dr. Walter Charleton,
_Physiologia Epicuro Gassendo-Charltoniana_ (Lond., 1654), p. 375. Compare
p. 63, line 3.
[44] PAGE 7, LINE 33. Page 7, line 43. _Thomas Hariotus_, etc.--The four
Englishmen named were learned men who had contributed to navigation by
magnetic observations. Harriot's account of his voyage to Virginia is
printed in Hakluyt's _Voyages_. Robert Hues (or Hood) wrote a treatise _on
Globes_, the Latin edition of which appeared in 1593 (dedicated to Sir
Walter Raleigh), and the English edition in 1638. It was republisht by the
Hakluyt Society, 1889. Edward Wright, the mathematician and writer on
navigation, also wrote the preface to Gilbert's own book. Abraham Kendall,
or Abram Kendal was "Portulano," or sailing-master of Sir Robert Dudley's
ship the _Bear_, and is mentioned in Dudley's _Arcano del Mare_. On the
return of Dudley's expedition in 1595, he joined Drake's last expedition,
which sailed that year, and died on the same day as Drake himself, 28
January, 1596. (See _Hakluyt_, ed. 1809, iv., p. 73.)
[45] PAGE 7, LINE 36. Page 8, line 1. _Guilielmus Borough._--Borough's book
has the title: _A Discours of the Variation of the Cumpas, or magneticall
{20} Needle. Wherein is Mathematically shewed, the manner of the
obseruation, effectes, and application thereof, made by W. B._ And is to be
annexed to _The Newe Attractive_ of R. N., 1581 (London).
[46] PAGE 7, LINE 37. Page 8, line 2. _Guilielmus Barlo_.--Archdeacon
William Barlowe (author, in 1616, of the _Magneticall Aduertisements_)
wrote in 1597 a little work called _The Navigators Supply_. It gives a
description of the ordinary compass, and also one of a special form of
meridian compass provided with sights for taking the bearings by the sun.
[47] PAGE 7, LINE 37. Page 8, line 3. _Robertus Normannus_. See Note to p.
5.
[48] PAGE 8, LINE 14. Page 8, line 21. _illo fabuloso Plinij bubulco_.--The
following is Pliny's account from Philemon Holland's English version of
1601 (p. 586): "As for the name Magnes that it hath, it tooke it (as
_Nicander_ saith) of the first inventor and deviser thereof, who found it
(by his saying) upon the mountaine Ida (for now it is to be had in all
other countries, like as in Spaine also;) and (by report) a Neat-heard he
was: who, as he kept his beasts upon the aforesaid mountaine, might
perceive as he went up and downe, both the hob-nailes which were on his
shoes, and also the yron picke or graine of his staffe, to sticke unto the
said stone."
[49] PAGE 9, LINE 22. Page 9, line 30. _Differentiæ priscis ex
colore_.--Pliny's account of the loadstones of different colours which came
from different regions is mainly taken from Sotacus. The white magnet,
which was friable, like pumice, and which did not draw iron, was probably
simply magnesia. The blue loadstones were the best. See p. 587 of Holland's
translation of Pliny, London, 1601. St. Isidore (_Originum seu
Etymologiarum_, lib. xvi., cap. 4) says: "Omnis autem magnes tanta melior
est, quanto [magis] cæruleus est."
[50] PAGE 10, LINE 29. Page 10, line 42. _Suarcebergo ... Snebergum &
Annæbergum_.--In the Stettin editions of 1628 and 1633 these are spelled
_Swarcebergs ... Schnebergum & Annebergum_. The Cordus given as authority
for these localities is Valerius Cordus, the commentator on Dioscorides.
[51] PAGE 11, LINE 3. Page 11, line 12. _Adriani Gilberti viri
nobilis_.--"Adrian Gylbert of Sandridge in the Countie of Devon, Gentleman"
is the description of the person to whom Queen Elizabeth granted a patent
for the discovery of a North-West passage to China. See Hakluyt's
_Voyages_, vol. iii., p. 96.
[52] PAGE 11, LINE 17. Page 11, line 28. _Dicitur a Græcis_ [Greek:
êraklios].--The discussion of the names of the magnet in different
languages by Gilbert in this place is far from complete. He gives little
more than is to be found in Pliny. For more complete discussions the reader
is referred to Buttmann, _Bemerkungen über die Benennungen einiger
Mineralien bei den Alten, vorzüglich des Magnetes und des Basaltes_ (Musæum
der Alterthumswissenschaft, Bd. II., pp. 5-52, and 102-104, 1808); G.
Fournier, _Hydrographie_ (livre xi., chap. I, 1643); Ulisse Aldrovandi,
_Musæum Metallicum_ (Bononiæ, 1648, lib. iv., cap. 2, p. 554); Klaproth,
_Lettre à M. le Baron A. de Humboldt, sur l'invention de la Boussole_,
Paris, 1834; T. S. Davies, _The History of Magnetical Discovery_ (Thomson's
_British Annual_, 1837, pp. 250-257); Th. Henri Martin, _De l'Aimant, de
ses noms divers et de ses variétés suivant les Anciens_ (Mémoires présentés
par divers savants a l'Academie des Inscriptions et Belles-lettres, I^{re}
série, t. vi., I^{re} partie, 1861); G. A. Palm, _Der Magnet in Alterthum_
(Programm des k. württembergischen Seminars Maulbronn, Stuttgart, {21}
1867). Of these works, those of Klaproth and of Martin are by far the most
important. Klaproth states that in modern Greek, in addition to the name
[Greek: magnêtis], the magnet also has the names [Greek: adamas] and
[Greek: kalamita]. The former of these, in various forms, _adamas_,
_adamant_, _aimant_, _yman_, and _piedramon_, has gone into many languages.
Originally the word [Greek: adamas] (the unconquered) was applied by the
Greeks to the hardest of the metals with which they were acquainted, that
is to say, to hard-tempered iron or steel, and it was subsequently because
of its root-signification also given by them to the diamond for the same
reason; it was even given to the henbane because of the deadly properties
of that plant. In the writings of the middle ages, in St. Augustine, St.
Isidore, Marbodeus, and even in Pliny, we find some confusion between the
two uses of _adamas_ to denote the loadstone as well as the diamond.
Certainly the word _adamas_, without ceasing to be applied to the diamond,
also designated the loadstone. At the same time (says Martin) the word
_magnes_ was preserved, as Pliny records, to designate a loadstone of
lesser strength than the _adamas_. On the other hand, the word _diamas_, or
_deamans_, had already in the thirteenth century been introduced into Latin
to signify the diamond as distinguisht from the magnet. _Adamas_ was
rendered _aymant_ in the romance version of the poem of Marbodeus on stones
(see Beckmann's variorum edition of 1799, p. 102), and in this form it was
for a time used to denote both the magnet and the diamond. Then it
gradually became restricted in use to the stone that attracts iron.
Some confusion has also arisen with respect to the Hebrew name of the
magnet. Sir W. Snow Harris makes the following statement (_Magnetism_, p.
5): "In the Talmud it [the loadstone] is termed _achzhàb'th_, the stone
which attracts; and in their ancient prayers it has the European name
_magn[=e]s_." On this point Dr. A. Löwy has furnisht the following notes.
The loadstone is termed in one of the Talmudical sections and in the
Midrash, _Eben Shoebeth_ (lapis attrahens). This would of course be written
[Hebrew: 'BN SHW'BT]. Omitting the [Hebrew: W] which marks the participial
construction, the words would stand thus: [Hebrew: 'BN SH'BT] A person
referring to Buxtorf's _Lexicon_ Talmudicum would in the index look out for
"Lapis magnesius," or for "magnes." He would then, in the first instance,
be referred to the two words already quoted. Not knowing the value of the
letters of the Hebrew alphabet, he reads [Hebrew: 'BN SH'BT] thus: [Hebrew:
'KZSH'BT] achzhab'th. It is true that Buxtorf has inserted in his _Lexicon_
the vocable [Hebrew: MAGNIYSEIS], "corruptum ex gr. [Greek: magnês,
magnêtês, magnêtis], named after the Asiatic city Magnesia." He goes on to
say, "Inde Achilles Statius istum lapidem vocavit [Greek: magnêsian
lithon]. Hinc [Hebrew: 'BN HMGNJSS CHMSHWK HBRZL]. Lapis Magnesius trahit
ferrum." Here he quotes from (Sepher) Ikkarem IV., cap. 35.
Kircher, in his _Magnes, sive de Arte magnetica_ (Coloniæ, 1643), gives
several other references to Hebrew literature. Others have supposed that
the word [Hebrew: CHLMYSH] _khallamish_, which signifies pebble, rock, or
hard rock, to be used for the magnet.
As to the other Greek name, [Greek: sidêritis], or [Greek: lithos
sidêritis] this was given not only to the loadstone but also to
non-magnetic iron. In the _Etymologicum magnum_ (under the word [Greek:
magnêtis]), and in Photius (_Quæst. amphiloch._, q. 131), it is stated that
the name _sideritis_ was given to the loadstone either because of its
action on iron, or of its resemblance in aspect to iron, _or rather_, they
say, _because the loadstone was originally found in the mines of this
metal_. Alexander of Aphrodisias expressly says (_Quætiones Physicæ_, II.
23) that {22} the loadstone appears to be nothing else than [Greek: gê
sidêritis], the earth which yields iron, or the earth of iron.
[53] PAGE 11, LINE 19. Page 11, line 29. _ab Orpheo_.--The reference is to
v. 301-328 of the [Greek: Lithika]. The passage, as given in Abel's edition
(Berol., 1881), begins:
[Greek: Tolma d' athanatous kai henêei meilissethai]
[Greek: magnêssêi, tên d' exoch' ephilato thousios Arês,]
[Greek: houneken, hoppote ken pelasêi polioio sidêrou,]
[Greek: êute parthenikê terenochroa chersin helousa]
[Greek: êitheon sternôi prosptussetai himeroenti,]
[Greek: hôs hêg' harpazousa poti spheteron demas haiei]
[Greek: aps palin ouk ethelei methemen polemista sidêron.]
[54] PAGE 11, LINE 20. Page 11, line 31. _Gallis aimant_.--The French word
_aimant_, or _aymant_, is generally supposed to be derived from _adamas_.
Nevertheless Klaproth (_op. citat._, p. 19) suggests that the word _aimant_
is a mere literal translation into French of the Chinese word _thsu chy_,
which is the common name of the magnet, and which means _loving stone_, or
_stone that loves_. All through the east the names of the magnet have
mostly the same signification, for example, in Sanskrit it is _thoumbaka_
(the kisser), in Hindustani _tchambak_.
[55] PAGE 11, LINE 20. Page 11, line 32. _Italis calamita_.--The name
_calamita_, universal in Italian for the magnet, is also used in Roumanian,
Croatian, Bosnian, and Wendish. Its supposed derivation from the Hebrew
_khallamîsh_ is repudiated by Klaproth, who also points out that the use of
[Greek: kalamita] in Greek is quite modern. He adds that the only
reasonable explanation of the word _calamita_ is that given by Father
Fournier (_op. citat._), who says:
"Ils (les marins français) la nomment aussi _calamite_, qui proprement en
français signifie une _grenouille verte_, parce qu'avant qu'on ait trouvé
l'invention de suspendre et de balancer sur un pivot l'aiguille aimantée,
nos ancêtres l'enfermaient dans une fiole de verre demi-remplie d'eau, et
la faisaient flotter, par le moyen de deux petits fétus, sur l'eau comme
une grenouille." Klaproth adds that he entirely agrees with the learned
Jesuit, but maintains that the word _calamite_, to designate the little
green frog, called to-day _le graisset_, _la raine_, or _la rainette_, is
essentially Greek. For we read in Pliny (_Hist. Nat._ lib. xxxii., ch. x.):
"Ea rana quam Græci _calamiten_ vocant, quoniam inter arundines,
fruticesque vivat, minima omnium est et viridissima."
[56] PAGE 11, LINE 20. Page 11, line 32. _Anglis_ loadstone & adamant
stone.
The English term _loadstone_ is clearly connected with the Anglo-Saxon verb
_loedan_, to lead, and with the Icelandic _leider-stein_. There is no doubt
that the spelling _lodestone_ would be etymologically more correct, since
it means _stone that leads_ not _stone that carries a load_. The correct
form is preserved in the word _lode-star_.
The word _adamant_, from _adamas_, the mediæval word for both loadstone and
diamond, also occurs in English for the loadstone, as witness Shakespeare:
"You draw me, you hard-hearted adamant
But yet you draw not iron; for my heart
Is true as steel."
_Midsummer Night's Dream_, Act II, Scene 1.
[57] PAGE 11, LINE 21. Page 11, {23} line 33. _Germanis magness_, &
_siegelstein_. The Stettin edition of 1628 reads _Germanis_ MAGNETSTEIN,
_Belgis_ SEYLSTEEN; while that of 1633 reads _Germanis_ MAGNETSTEIN,
_Belgis_ SYLSTEEN.
[58] PAGE 11, LINE 26. Page 11, line 39. In this line the Greek sentence
is, in every known copy of the folio of 1600, corrected in ink upon the
text, [Greek: thalês] being thus altered into [Greek: Thalês], and [Greek:
apomnemonuousi] into [Greek: apomnemoneuousi]. Four lines lower, brackets
have been inserted around the words (lapidum specularium modo). These ink
corrections must have been made at the printers', possibly by Gilbert's own
hand. They have been carried out as errata in the editions of 1628 and
1633. The "facsimile" Berlin reprint of 1892 has deleted them, however.
Other ink corrections on pp. 14, 22, 38, 39, 47, 130, and 200 of the folio
edition of 1600 are noted in due course.
[59] PAGE 11, LINE 29. Page 11, line 45. _lapis specularis_. This is the
mediæval name for _mica_, but in Elizabethan times known as talc or muscovy
stone. Cardan, _De Rerum Varietate_ (Basil., 1557, p. 418), lib. xiiii.,
cap. lxxii., mentions the use of _lapis specularis_ for windows.
[60] PAGE 11, LINE 31. Page 11, line 46.: _Germanis Katzensilbar_ &
_Talke_.--In the editions of 1628 and 1633 this is corrected to _Germanis_
KATZENSILBER & TALCKE. Goethe, in _Wilhelm Meister's Travels_, calls mica
"cat-gold."
[61] PAGE 12, LINE 30. Page 12, line 35. _integtum_ appears to be a
misprint for _integrum_, which is the reading of editions 1628 and 1633.
[62] PAGE 13, LINE 4. Page 13, line 3. [Greek: mikrogê] _seu Terrella_.
Although rounded loadstones had been used before Gilbert's time (see
Peregrinus, p. 3 of Augsburg edition of 1558, or Baptista Porta, p. 194, of
English edition of 1658), Gilbert's use of the spherical loadstone as a
model of the globe of the earth is distinctive. The name _Terrella_
remained in the language. In _Pepys's Diary_ we read how on October 2,
1663, he "received a letter from Mr. Barlow with a terella." John Evelyn,
in his _Diary_, July, 1655, mentions a "pretty terella with the circles and
showing the magnetic deviations."
A Terrella, 4½ inches in diameter, was presented in 1662 by King Charles I.
to the Royal Society, and is still in its possession. It was examined in
1687 (see _Phil. Transactions_ for that year) by the Society to see whether
the positions of its poles had changed.
In Grew's _Catalogue and Description of the Rarities belonging to the Royal
Society and preserved at Gresham College_ (London, 1681, p. 364) is
mentioned a Terrella contrived by Sir Christopher Wren, with one half
immersed in the centre of a plane horizontal table, so as to be like a
Globe with the poles in the horizon, having thirty-two magnet needles
mounted in the margin of the table to show "the different respect of the
_Needle_ to the several _Points_ of the _Loadstone_."
In Sir John Pettus's _Fleta Minor_, London, 1683, in the _Dictionary of
Metallick Words_ at the end, under the word _Loadstone_ occurs the
following passage:
"Another piece of Curiosity I saw in the Hands of Sir _William Persal_
(since Deceased also) _viz._, a _Terrella_ or _Load-stone_, of little more
than _6 Inches Diameter_, turned into a _Globular Form_, and all the
_Imaginery Lines_ of our _Terrestrial Globe_, exactly drawn upon it: _viz._
the _Artick _ and _Antartick Circles_, the _two Tropicks_, the _two
Colures_, the _Zodiack_ and _Meridian_; and these _Lines_, and the several
_Countryes_, artificially _Painted_ on it, and all of them with their true
_Distances_, from the two _Polar Points_, and to find the truth of those
_Points_, he took two _little pieces_ of a _Needle_, each of about _half_
{24} _an Inch in length_, and those he laid on the _Meridian line_, and
then with _Brass Compasses_, moved one of them towards the _Artick_, which
as it was moved, still raised it self at one end higher and higher, keeping
the other end fixt to the _Terrella_; and when it had compleated it Journy
to the very _Artick Points_, it stood upright upon that _Point_; then he
moved the other piece of _Needle_ to the _Antartick Point_, which had its
_Elevations_ like the other, and when it came to the _Point_, it fixt it
self upon that _Point_, and stood _upright_, and then taking the _Terrella_
in my Hand, I could perfectly see that the two _pieces_ of _Needles_ stood
so exactly one against the other, as if it had been one intire _long
Needle_ put through the _Terrella_, which made me give credit to those who
held, That there is an _Astral Influence_ that _darts_ it self through the
_Globe_ of _Earth_ from _North_ to _South_ (and is as the _Axel-Tree_ to
the _Wheel_, and so called the _Axis_ of the _World_) about which the
_Globe_ of the _Earth_ is turned, by an _Astral Power_, so as what I
thought _imaginary_, by this _Demonstration_, I found _real_."
[63] PAGE 13, LINE 20. Page 13, line 22. The editions of 1628 and 1633 give
a different woodcut from this: they show the terrella lined with meridians,
equator, and parallels of latitude: and they give the compass needle, at
the top, _pointing in the wrong direction_.
[64] PAGE 14, LINE 3. Page 14, line 3. The Berlin "facsimile" reprint omits
the asterisk here.
[65] PAGE 14, LINE 5. Page 14, line 6. _erectus_ altered in ink in the
folio to _erecta_. But _erectus_ is preserved in editions 1628 and 1633. In
Cap. IIII., on p. 14, both these Stettin editions insert an additional cut
representing the terrella A placed in a tub or vessel B floating on water.
[66] PAGE 14, LINE 34. Page 14, line 39. _variatione quad[=a]._ The whole
of Book IIII. is devoted to a discussion of the variation of the compass.
[67] PAGE 16, LINE 28. Page 16, line 34. _aquæ._--This curious use of the
dative occurs also on p. 222, line 8.
[68] PAGE 17, LINE 1. Page 17, line 1. _videbis._--The reading _vibebis_ of
the 1633 edition is an error.
[69] PAGE 18, LINE 24. Page 18, line 27. _Theamedem._--For the myth about
the alleged _Theamedes_, or repelling magnet, see Cardan, _De Subtilitate_
(folio ed., 1550, lib. vii., p. 186).
Pliny's account, in the English version of 1601 (p. 587), runs:
"To conclude, there is another mountaine in the same Æthyopia, and not
farre from the said Zimiris, which breedeth the stone Theamedes that will
abide no yron, but rejecteth and driveth the same from it."
Martin Cortes, in his _Arte de Nauegar_ (Seville, 1556), wrote:
"And true it is that Tanxeades writeth, that in Ethiope is found another
kinde of this stone, that putteth yron from it" (Eden's translation,
London, 1609).
[70] PAGE 21, LINE 24. Page 21, line 25. _Hic segetes, &c._--The English
version of these lines from Vergil's _Georgics_, Book I., is by the late
Mr. R. D. Blackmore.
[71] PAGE 22, LINE 18. Page 22, line 19. _quale_, altered in ink in the
folio text to _qualis_. The editions of 1628 and 1633 both read _qualis_.
[72] PAGE 22, LINE 19. Page 22, line 20. _rubrica fabrili_: in English
_ruddle_ or _reddle_. See "Sir" John Hill, _A General Natural History_,
1748, p. 47. In the _De Re Metallica_ of Entzelt (Encelius), Frankfurt,
1551, p. 134, is a paragraph headed _De Rubrica Fabrili_, as follows:
"Rubrica fabrilis duplex {25} est. à Germanis añt utraque dicitur rottel,
röttelstein, wie die zimmerleüt vnd steynmetzen brauchen. à Græcis [Greek:
miltos tektonikê]. Est enim alia nativa, alia factitia. Natiua à Germanis
propriè dicitur berckrottel. haec apud nos est fossilis.... Porro factitia
est rubrica fabrilis, à Germanis braunrottel, quæ fit ex ochra usta, ut
Theophrastus et Dioscorides testantur."
[73] PAGE 22, LINE 19. Page 22, line 20. _In Sussexia Angliæ._--In Camden's
_Britannia_ (1580) we read concerning the iron industry in the villages in
Sussex: "They are full of iron mines in sundry places, where, for the
making and founding thereof, there be furnaces on every side; and a huge
deal of wood is yearly burnt. The heavy forge-hammers, worked by
water-power, stored in hammer-ponds, ceaselessly beating upon the iron,
fill the neighbourhood round about, day and night, with continual noise."
[74] PAGE 23, LINE 1. Page 22, line 44. _in libro Aristotelis de admirandis
narrationibus._--The reference is to the work usually known as the _De
Mirabilibus Auscultationibus_, Cap. XLVIII.: "Fertur autem peculiarissima
generatio esse ferri Chalybici Amisenique, ut quod ex sabulo quod a fluviis
defertur, ut perhibent certe, conflatur. Alii simpliciter lotum in fornace
excoqui, alii vero, quod ex lotura subsedit, frequentius lotum comburi
tradunt adjecto simul et pyrimacho dicto lapide, qui in ista regio plurimus
reperiri fertur." (Ed. Didot, vol. ii., p. 87.) According to Georgius
Agricola, the stone pyrimachus is simply iron pyrites.
[75] PAGE 23, LINE 22. Page 23, line 23. _vt in Italia Comi_, &c.--This is
mostly taken from Pliny. Compare the following passage from Philemon
Holland's translation (1601), p. 514:
"But the most varietie of yron commeth by the meanes of the water, wherein
the yron red-hot is eftsoones dipped and quenched for to be hardened. And
verely, water only which in some place is better, in other worse, is that
which hath ennobled many places for the excellent yron that commeth from
them, as namely, Bilbilis in Spaine, and Tarassio, Comus also in Italie;
for none of these places have any yron mines of their owne, and yet there
is no talke but of the yron and steele that commeth from thence."
Bilbilis is Bambola, and Tariassona the Tarazona of modern Spain.
[76] PAGE 24, LINE 28. Page 24, line 27. _Quare vani sunt illi
Chemici._--Gilbert had no faith in the alchemists. On pp. 19 and 21 he had
poked fun at them for declaring the metals to be constituted of sulphur and
quicksilver, and for pronouncing the fixed earth in iron to be sulphur. On
p. 20 he had denied their proposition that the differences between silver,
gold, and copper could arise from proportions of their constituent
materials; and he likewise denounced unsparingly the supposed relation
between the seven metals and the seven planets. He now denounces the vain
dreams of turning all metals into gold, and all stones into diamonds. Later
he rejects as absurd the magnetic curing of wounds. His detachment from the
pseudo-science of his age was unique if not complete.
[77] PAGE 25, LINE 15. Page 25, line 16. _Petro-coriis, & Cabis
Biturgibus._--The Petro-corii were a tribe in the neighbourhood of
Perigord; the Cubi Biturges another in that of Bourges.
[78] PAGE 25, LINE 21. Page 25, line 23. Pliny's account, as translated by
P. Holland (ed. 1601, p. 515), runs thus:
"Of all mines that be, the veine of this mettall is largest, and spreadeth
it selfe into most lengths every way: as we may see in that part of Biscay
that coasteth along the sea, and upon which the Ocean beateth: where there
{26} is a craggie mountaine very steep and high, which standeth all upon a
mine or veine of yron. A wonderfull thing, and in manner incredible,
howbeit, most true, according as I have shewed already in my Cosmographie,
as touching the circuit of the Ocean."
[79] PAGE 26, LINE 15. Page 26, line 12. _quas Clampas nostri vocant._--The
name _clamp_ for the natural kiln formed by heaping up the bricks, with
ventilating spaces and fuel within the heap, is still current.
[80] PAGE 26, LINE 39. Page 26, line 38. _Pluebat in Taurinis ferrum._--The
occurrence is narrated by Scaliger, _De Subtilitate_, Exercitat. cccxxiii.:
"Sed falsò lapidis pluviam creas tu ex pulvere hausto à nubibus, atque in
lapidem condensato. At ferrum, quod pluit in Taurinis, cuius frustum apud
nos extat, qua ex fodina sustulit nubes? Tribus circiter annis antè, quàm
ab Rege provincia illa recepta esset, pluit ferro multis in locis, sed
raris" (p. 434, Editio Lutetiæ, 1557).
"During the latter ages of the Roman Empire the _city_ of Augusta
Taurinorum seems to have been commonly known (as was the case in many
instances in Transalpine Gaul) by the name of the tribe to which it
belonged, and is called simply Taurini in the Itineraries, as well as by
other writers, hence its modern name of Torino or Turin" (Smith's
_Dictionary of Greek and Roman Geographies_, p. 1113).
There exists a considerable literature respecting falls of meteors and of
meteoric iron. Livy, Plutarch, and Pliny all record examples. See also
_Remarks concerning stones said to have fallen from the clouds_, by Edward
King (London, 1796); Chladni, _Ueber den Ursprung der von Pallas gefundenen
und anderer ihr ähnlicher Eisenmassen_ (Riga, 1794); _Philosophical
Transactions_, vol. lxxviii., pp. 37 and 183; vol. lxxxv., p. 103; vol.
xcii., p. 174; Humboldt's _Cosmos_, vol. i. (p. 97 of London edition,
1860); C. Rammelsberg, _Die chemische Natur der Meteoriten_ (Berlin, 1879);
Maskelyne, _Some lecture-notes on Meteorites_ printed in _Nature_, vol.
xii., pp. 485, 504, and 520, 1875. Maskelyne denominates as _siderites_
those meteorites which consist chiefly of iron. They usually contain from
80 to 95 per cent. of iron, often alloyed with nickel. This meteoric iron
is sometimes so pure that it can at once be forged by the smith. An
admirable summary of the whole subject is to be found in L. Fletcher's _An
Introduction to the study of Meteorites_, publisht by the British Museum
(Nat. Hist.), London, 1896.
[81] PAGE 27, LINE 3. Page 26, line 41. _vt Cardanus ... scribit._--The
passage runs:
"Vidimus anno MDX cum cecidisset è coelo lapides circiter MCC in agrum
fluvio Abduæ conterminum, ex his unum CXX pondo, alium sexaginta delati
fuerunt ad reges Gallor[~u] satrapes, plurimi: colos ferrugineus, durities
eximia, odor sulphureus" (Cardan, _De Rerum Varietate_, lib. xiiii., cap.
lxxii.; Basil., 1557, p. 545).
[82] PAGE 27, LINE 9. Page 27, line 2. _aut stannum, aut plumbum album._
Although most authorities agree in translating _plumbum album_ or _plumbum
candidum_ as "tin" (which is unquestionably the meaning in such examples as
Pliny's _Nat. Hist._, xxxiv. 347, and iv. 16; or Strabo, iii. 147),
nevertheless it is certain that here _plumbum album_ is not given as a
synonym of _stannum_ and therefore is not _tin_. That Gilbert meant either
spelter or pewter is pretty certain. He based his metallic terms mainly
upon Encelius (Christoph Entzelt) whose _De Re Metallica_ was published at
Frankfurt in 1551. From this work are taken the following passages: {27}
p. 61. _De Plumbo candido._ Cap. XXXI.
"Veluti plumbum nigr[~u] uocatur à Germanis blei simpliciter, od'
schwartzblei: ita plumb[~u] candid[~u] ab his uocatur weissblei, od' ziñ.
Impropriè autem plumbum hoc nostrum candidum ziñ, stannum dicitur. Et non
sunt idem, ut hactenus voluerunt, stannum et plumbum candidum, unser ziñ.
Aliud est stannum, de quo mox agemus: et aliud plumbum candidum nostrum,
unser ziñ, quod nigro plumbo quasi est quiddã purius et perfectius...."
p. 62. _De Stanno._ Cap. XXXII.
"In præcedenti capite indicauimus aliud esse stannum, aliud esse plumb[~u]
candid[~u]. Illa ergo definitio plumbi candidi, dess zinnes, etiã apud
chimistas nõ de stanno, sed de plumbo candido (ut mihi uidetur)
intelligenda est, cum dicunt: Stannum (es soll heyssen plumbum candidum)
est metallicum album, non purum, lividum...."
p. 63. "Sic uides stannum, secundum Serapionem, metallicum esse quod
reperitur in sua propria uena, ut forsitan apud nos bisemut[~u]: ecõtra
nostr[~u] candid[~u] plumb[~u], est Plinij candid[~u] plumb[~u], das zin,
quod cõflatur ut plumbum nigrum, ex pyrite, galena, et lapillis nigris.
Deinde uides stannum Plinio esse quiddã de plumbo nigro, nempe primum
fluorem plumbi nigri, als wann man vnser bley ertz schmeltzet, das erst das
do fleüsset, zwäre Plinio stannum. Et hoc docet Plinius adulterari pl[~u]bo
candido, mit vnserm zinn, vnd wann du ihm recht nachdenckest, daruon die
kannen gemacht werden, das man halbwerck heist.... O ir losen vngelerten,
vnckenbrenner. Stannum proculdubio Arabis metallum est preciosius nostro
candido plumbo: sicuti apud nos bisemuthum quiddam plumbo preciosius."
[83] PAGE 27, LINE 21. Page 27, line 17. _venas ... venis._--It is
impossible to give in English this play on words between veins of ore and
veins of the animal body.
[84] PAGE 28, LINE 23. Page 28, line 20. _quem nos verticitatem
dicimus._--See the notes on Gilbert's glossary, _ante_. The word verticity
remained in the language. On p. 140 of Joseph Glanvill's _Vanity of
Dogmatizing_ (Lond., 1661) we read: "We believe the _verticity_ of the
_Needle_, without a Certificate from the _dayes_ of _old_."
[85] PAGE 29, LINE 15. Page 29, line 16. _Nos verò diligentiùs omnia
experientes._--The method of carefully trying everything, instead of
accepting statements on authority, is characteristic of Gilbert's work. The
large asterisks affixed to Chapters IX. X. XI. XII. and XIII. of Book I.
indicate that Gilbert considered them to announce important original
magnetical discoveries. The electrical discoveries of Book II., Chapter
II., are similarly distinguished. A rich crop of new magnetical
experiments, marked with marginal asterisks, large and small, is to be
found in Book II., from Chapter XV. to Chapter XXXIV.; while a third series
of experimental magnetical discoveries extends throughout Book III.
[86] PAGE 31, LINE 30. Page 31, line 25. _verticem._--The context and the
heading of the Chapter appear to require _verticitatem_. All editions,
however, read _verticem_.
[87] PAGE 32, LINE 12. Page 32, line 9. _Gartias ab horto._--The passage
from Gartias ab Horto runs as follows in the Italian edition of 1616,
_Dell' Historia dei Semplici Aromati._... di Don Garzia dall' Horto, Medico
Portughese, ... Venezia MDCXVI., p. 208.
"Nè meno è questa pietra velenosa, si come molti hanno tenuto; imperoche le
genti di queste bande dicono che la Calamita presa per bocca, però in poca
{28} quantità, conserva la gioventù. La onde si racconta, che il Re di
Zeilan il vecchio' s'haveva fatto fare tutti i vasi, dove si cocevano le
vivãde per lui, di Calamita. Et questo lo disse à me colui proprio, che fu
à questo officio destinato."
[88] PAGE 32, LINE 29. Page 32, line 29. _Plutarchus & C. Ptolemæus._--The
garlick myth has already been referred to in the note to p. 1. The
originals are Plutarch, _Quæstiones Platonicæ_, lib. vii., cap. 7, § 1; C.
Ptolemæus, _Opus Quadripartitum,_ bk. i., cap. 3. The English translation
of the latter, by Whalley (London, 1701), p. 10, runs: "For if the
_Loadstone_ be _Rubbed_ with _Garlick_, the _Iron will not be drawn by
it_."
[89] PAGE 32, LINE 32. Page 32, line 33. _Medici nonnulli._--This is
apparently a reference to the followers of Rhazes and Paracelsus. The
argument of Gilbert as to the inefficacy of powdered loadstones is
reproduced more fully by William Barlowe in his _Magneticall
Aduertisements_ (1616, p. 7), as follows:
"It is the goodnesse of the _Loadstone_ ioyned with a fit forme that will
shew great force. For as a very good forme with base substance can doe but
very litle, so the substance of the _Loadstone_ bee it neuer so excellent,
except it haue some conuenient forme, is not auaileable. For example, an
excellent _loadstone_ of a pound waight and of a good fashion, being vsed
artificially, may take vp foure pounds of Iron; beate it into small pouder,
and it shall bee of no force to take vp one ounce of Iron; yea I am very
well assured that halfe an ounce of a Loadstone of good fashion, and of
like vertue will take vp more then that pound will doe being beaten into
powder. Whence (to adde this by the way) it appeareth manifestly, that it
is a great error of those Physitions and Surgeons, which to remedy
ruptures, doe prescribe vnto their Patients to take the pouder of a
_Loadstone_ inwardly, and the small filing of iron mingled in some plaister
outwardly: supposing that herein the _magneticall_ drawing should doe great
wonders."
[90] PAGE 33, LINE 11. Page 33, line 8. _Nicolaus in emplastrum
divinum._...--Nicolaus Myrepsus is also known as Præpositas. In his _Liber
de compositione medicamentorum_ (Ingoldstat, 1541, 4to) are numerous
recipes containing loadstone: for example, Recipe No. 246, called "esdra
magna," is a medicine given for inflammation of the stomach and for
strangury, compounded of some forty materials including "litho demonis" and
"lapis magnetis." The _emplastrum divinum_ does not, however, appear to
contain loadstone. In the English tractate, _Præpositas his Practise, a
worke ... for the better preservation of the Health of Man. Wherein are ...
approved Medicines, Receiptes and Ointmentes. Translated out of Latin in to
English by_ L. M. (London, 1588, 4to), we read on p. 35, "An Emplaister of
D. N. [Doctor Nicolaus] which the Pothecaries call Divinum." This contains
litharge, bdellium, and "green brasse," but no loadstone.
Luis de Oviedo in his treatise _Methodo de la Coleccion y reposicion de las
Medicinas simples_, edited by Gregorio Gonçalez, Boticario (Madrid, 1622),
gives (p. 502) the following: "Emplasto de la madre. _Recibe_: Nuezes
moscadas, clauos, cinamono, artemisia, piedraimon. De cada uno dos
onças.... Entre otras differencias que ay de piedraiman se hallan dos. Vna
que por la parte que mira al Septentrion, atrae el hierro, por lo quel se
llama magnes ferrugineus. Y otra que atrae la carne, a la qual llaman
magnes creaginus."
An "Emplastrum sticticum" containing amber, mummy, loadstone, {29}
hæmatite, and twenty other ingredients, and declared to be "vulnerum
ulcerumque telo inflictorum sticticum emplastrum præstantissimum," is
described on p. 267 of the _Basilica chimica_ of Oswaldus Crollius
(Frankfurt, 1612).
[91] PAGE 33, LINE 12. Page 33, line 9. _Augustani ... in emplastrum
nigrum_....--Amongst the physicians of the Augsburg school the most
celebrated were Adolphus Occo, Ambrosio Jung, and Gereone Seyler. This
particular reference is to the _Pharmacopoeia Augustana_ ... _a Collegio
Medico recognita_, published at Augsburg, and which ran through many
editions. The recipe for the "_emplastrum nigrum vulgo Stichpflaster_" will
be found on p. 182 of the seventh edition (1621-2). The recipe begins with
oil of roses, colophony, wax, and includes some twenty-two ingredients,
amongst them mummy, dried earthworms, and two ounces _lapidis magnetis
præparati_. The recipe concludes: "Fiat Emplastrum secundùm artem. Perquàm
efficax ad recentia vulnera et puncturas, vndè denominationem habet." The
volume is a handsome folio not unlike Gilbert's own book, and bears at the
end of the prefatory address _ad Lectorem_ identically the same _cul de
lampe_ as is found on p. 44 of _De Magnete_.
The contradictions as to the alleged medicinal virtues of loadstone are
well illustrated by Galen, who in his _De facultatibus_ says that loadstone
is like hæmatite, which is astringent, while in his _De simplici medicina_
he says it is purgative.
[92] PAGE 33, LINE 14. Page 33, line 12. _Paracelsus in fodicationum
emplastrum_.--Paracelsus's recipe for a plaster against stab-wounds is to
be found in _Wundt vund Leibartznei_ ... D. Theoph. Paracelsus (Frankf.,
1555, pp. 63-67).
[93] PAGE 33, LINE 17. Page 33, line 15. _Ferri vis medicinalis_.--This
chapter on the medicinal virtues of iron is a summary of the views held
down to that time. Those curious to pursue the subject should consult
Waring's _Bibliotheca Therapeutica_ (London, 1878). Nor should they miss
the rare black-letter quarto by Dr. Nicholas Monardus, of Seville, _Joyfull
Newes out of the New-found Worlde_, translated by John Frampton (London,
1596), in which are recited the opinions of Galen, Rhazes, Avicenna, and
others, on the medicinal properties of iron. In addition to the views of
the Arabic authors, against whom his arguments are directed, Gilbert
discusses those of Joannes Manardus, Curtius, and Fallopius. The treatise
of Manardus, _Epistolarum medicinalium libri viginti_ (Basil., 1549), is a
_résumé_ of the works of Galen and the Arabic physicians, but gives little
respecting iron. Curtius (Nicolaus) was the author of a book, _Libellus de
medicamentis præparatibus et purgantibus_ (Giessæ Cattorum, 1614). The
works of Fallopius are _De Simplicibus Medicamentis purgentibus tractatus_
(Venet., 1566, 4to), and _Tractatus de Compositione Medicamentorum_
(Venet., 1570, 4to).
[94] PAGE 34, LINE 7. Page 34, line 3. _quorundã Arabum opiniones_.--The
Arabian authorities referred to here or elsewhere by Gilbert are:
_Albategnius_ (otherwise known as Machometes Aractensis), Muhammad Ibn
J[=a]bir, _Al-Batt[=a]n[=i]_.
_Avicenna_ (otherwise Abohali). Abou-'Ali al-'Hoséin ben-'Abd-Allah
Ibn-Sinâ, or, shortly, _Ibn Sîna._
_Averroes._ Muhammad Ibn Ahmed Ibn-Roschd, _Abou Al-Walíd._
_Geber._ Ab[=u] M[=u]s[=a] J[=a]bir Ibn Haiy[=a]n, _Al-Tars[=u]si._
_Hali Abas._ 'Alí Ibn Al-'Abbás, _Al Majúsi_. {30}
_Rhazes_, or _Rasis_. Muhammad Ibn Zakar[=i]y[=a].
_Serapio._ Yuhanná Ibn Sarapion.
_Thebit Ben-Kora_ (otherwise Thabit Ibn Corrah). Ab[=u] Thabit Ibn Kurrah,
_Al Harrani._
[95] PAGE 34, LINE 38.: Page 34, line 40. _electuarium de scoria ferri
descriptum à Raze._--Rhazes or Rasis, whose Arabic name was Muhammad Ibn
Zakar[=i]y[=a], wrote _De Simplicibus, ad Almansorem._ In Chap. 63 of this
work he gives a recipe for a stomachic, which includes fennel, anise,
origanum, black pepper, cinammon, ginger, and iron slag. In the splendid
folio work of Rhazes publisht at Venice in 1542, with the title _Habes
candide lector Contin[~e]tem Rasis_, Libri ultimi, cap. 295, under the
heading _De Ferro,_ are set forth the virtues of iron slag: "Virtus scorie
est sicut virtus scorie [a]eris sed debilior in purgãdo: et erugo ferri
est stiptica: et c[~u] superpositur retinet fluxus menstruor[~u].... Ait
Paulus: aqua in qua extinguitur ferr[~u] calens.... Dico: certificatus sum
experientia [~q] valet contra emorryodas diabetem et fluxum menstruorum."
[96] PAGE 35, LINE 16.: Page 35, line 13. _Paulus._--This is not Fra Paolo
Sarpi, nor Marco Polo, nor Paulus Jovius the historian, nor Paulus
Nicolettus Venetus, but Paulus Aeginæ.
[97] PAGE 35, LINE 29.: Page 35, line 28. _Sed malè Avicenna._--The advice
of Avicenna to administer a draught containing powdered loadstone, reads as
follows in the Giunta edition (Venice, 1608):
Lib. ii., cap. 470, p. 356. "Magnes quid est? Est lapis qui attrahit
ferrum, quum ergo aduritur, fit hæmatites, & virtus ejus est sicut virtus
illius.... Datur in potu [ad bibitionem limaturæ ferri, quum retinetur in
ventre scoria ferri. Ipse enim extrahit] ipsam, & associatur ei apud
exitum. Et dicitur, quando in potu sumuntur ex eo tres anulusat cum
mellicrato, educit solutione humorem grossum malum."
The passage is identical with that in the Venetian edition of 1486, in both
of which the liquid prescribed is mellicratus--mead. Gilbert says that the
iron is to be given in juice of _mercurialis_. Here he only follows
Matthiolus, who, in his _Commentaries on Dioscorides_, says (p. 998 of the
Basil. edition of 1598): "Sed (vt idem Auicenna scribit) proprium hujusce
ferrei pharmaci antidotum, est lapis magnes drachmæ pondere potus, ex
mercurialis, vel betæ succo."
Serapio, in his _De Simplicibus Medicinis_ (Brunfels' edition, Argentorati,
1531), p. 264, refers to Galen's prescription of iron scoriæ, and under the
article _de lapide magnetis_, p. 260, quotes Dioscorides as follows: "Et
uirtus huius lapidis est, ut quãdo dantur in potu duo onolosat ex eo c[~u]
melicrato, laxat humores grossos."
The original passage in Dioscorides, _De Materia Medica,_ ch. 147
(Spengel's edition of 1829) runs: "[Greek: Tou de magnêtou lithou aristos
estin ho ton sidêron eucherôs helkôn, kai tên chroan kuanizôn, puknos te
kai ouk agan barus. Dunamin de echei pachous agôgon didomenos meta
melikratou triôbolou baros; enioi de touton kaiontes anti haimatitou
pipraskousin.]."
In the Frankfurt edition of Dioscorides, translated by Ruellius (1543), the
passage is:
"Magnes lapis optimus est, qui ferrum facile trahit, colore ad coeruleum
uergente, densus, nec admodum gravis. Datur cum aqua mulsa, trium obolorum
pondere, ut crassos humores eliciat. Sunt qui magnetem cremat[=u] pro
hæmatite vendant...."
In the _Scholia_ of Joannes Lonicerus upon Dioscorides _In Dioscoridæ {31}
Anazarbei de re medica libros a Virgilio Marcello versos, Scholia nova,
Ioanne Lonicero autore_ (Marburgi, 1543, p. 77), occurs the following:
"_De recremento ferri._ Cap. XLIX.
"[Greek: Skôria sidêrou]. scoria vel recrementum ferri. Quæ per ignem à
ferro et cupro sordes separantur ac reijciuntur, et ab aliis metallis
[Greek: skôria] uocantur. Omnis scoria, maxime uero ferri exiccat. Acerrimo
aceto macerauit Galenus ferri scoriam, ac deinde excocto, pharmacum efficax
confecit ad purulentas quæ multo tempore uexatæ erant, aures, admirando
spectantium effectu. Ardenti scoria uel recrementum [Greek: helkusma],
inquit Galenus."
See also the _Enarrationes eruditissimæ_ of Amatus Lusitanus (Venet.,
1597), pp. 482 and 507, upon iron and the loadstone.
[98] PAGE 36, LINE 27. Page 36, line 29. _eijcitur_ for _ejicitur_.
[99] PAGE 37, LINE 18. Page 37, line 22. _ut Cardanus
philosophatur._--Cardan's nonsense about the magnet feeding on iron is to
be found in _De Subtilitate_, lib. vii. (Basil., 1611, p. 381).
[100] PAGE 38, LINE 4. Page 38, line 7. _ferramenta ... in usum
navigantium._--Compare Marke Ridley's _A Short Treatise of Magneticall
Bodies and Motions_ (Lond., 1613), p. _a2_ in the _Preface Magneticall_,
where he speaks of the "iron-workes" used in building ships. The
phraseology of Marke Ridley throws much light on the Latin terms used by
Gilbert.
[101] PAGE 38, LINE 36. Page 38, line 42. _vruntur;_ changed in ink to
_vrantur_ in the folio of 1600; but _uruntur_ appears in the editions of
1628 and 1633.
[102] PAGE 39, LINE 12. Page 39, line 12. _virumque;_ altered in ink to
_virunque_ in all copies of the folio edition of 1600.
[103] PAGE 40, LINE 32. Page 40, line 33. _ad tantos labores
exantlandos._--Pumping, as it was in mining before the invention of the
steam engine, may best be realized by examining the woodcuts in the _De re
metallica_ of Georgius Agricola (Basil., Froben, 1556).
[104] PAGE 40, LINE 34. Page 40, line 36. _quingentas orgyas._--Gilbert
probably had in his mind the works of the Rorerbühel, in the district of
Kitzbühl, which in the sixteenth century had reached the depth of 3,107
feet. See Humboldt's _Cosmos_ (Lond., 1860, vol. i., p. 149).
[105] PAGE 43, LINE 34. Page 43, line 33. _glis._--This word, here
translated _grit_, does not appear to be classical Latin; it may mean _ooze
or slime_.
[106] PAGE 45, LINE 25. Page 45, line 26. _Motus igitur ... quinque._ The
five kinds of magnetic motions correspond in fact to the remaining sections
of the book; as follows: _Coitio_, Book II.; _Directio_, Book III.;
_Variatio_, Book IV.; _Declinatio_, Book V.; and _Revolutio_, Book VI.
[107] PAGE 46, LINE 7. Page 46, line 8. _Jofrancus Offusius._--The
reference is to the treatise _De divina astrorum faculitate_ of Johannes
Franciscus Offusius (Paris, 1570).
[108] PAGE 47, LINE 15. Page 47, line 18. _Græci vocant_ [Greek: êlektron],
_quia ad se paleas trahit._ In this discussion of the names given to amber,
Gilbert apparently conceives [Greek: êlektron] to be derived from the verb
[Greek: helkein]; which is manifestly a doubtful etymology. There has been
much discussion amongst philologists as to the derivation of [Greek:
êlektron] or [Greek: êlektron], and its possible connection with the word
[Greek: êlektôr]. This discussion has been somewhat obscured by the
circumstance that the Greek authors unquestionably used [Greek: êlektron]
(and the Latins their word _electrum_) in two different significations,
some of them using these words to mean amber, others to mean a shining {32}
metal, apparently of having qualities between those of gold and silver, and
probably some sort of alloy. Schweigger, _Ueber das Elektron der Alten_
(Greifswald, 1848), has argued that this metal was indeed no other than
platinum: but his argument partakes too much of special pleading. Those who
desire to follow the question of the derivation of [Greek: êlektron] may
consult the following authorities: J. M. Gessner, _De Electro Veterum_
(Commentt. Soc. Reg. Scientt. Goetting., vol. iii., p. 67, 1753); Delaunay,
_Mineralogie der Alten_, Part II., p. 125; Buttmann, _Mythologus_ (Appendix
I., _Ueber das Elektron_), Vol. II., p. 355, in which he adopts Gilbert's
derivation from [Greek: helkein]; Beckmann, _Ursprung und Bedeutung des
Bernsteinnamens Elektron_ (Braunsberg, 1859); Th. Henri Martin, _Du Succin,
de ses noms divers et de ses variétés suivant les anciens_ (Mémoires de
l'Académie des Inscriptions et Belles-lettres, Tome VI., 1^{re} série,
1^{re} partie, 1860); Martinus Scheins, _De Electro Veterum Metallico_
(Inaugural dissertation, Berlin, 1871); F. A. Paley, _Gold Worship in
relation to Sun Worship_ (Contemporary Review, August, 1884). See also
Curtius, _Grundzüge der griechischen Etymologie_, pp. 656-659. The net
result of the disputations of scholars appears to be that [Greek: êlektôr]
(he who shines) is a masculine form to which there corresponds the neuter
form [Greek: êlektron] (that which shines). Stephanus admits the
accentuation used by Gilbert, [Greek: êlektron], to be justified from the
_Timæus_ of Plato; see Note to p. 61.
[109] PAGE 47, LINE 16. Page 47, line 19. [Greek: harpax] dicitur, &
[Greek: chrusophoron].--With respect to the other names given to amber, M.
Th. Henri Martin has written (see previous note) so admirable an account of
them that it is impossible to better it. It is therefore given here entire,
as follows:
"Le succin a reçu chez les anciens des noms très-divers. Sans parler du
nom de [Greek: lunkourion], lyncurium, qui peut-être ne lui appartient
pas, comme nous le montrerons plus loin, il s'est nommé chez les Grecs
le plus souvent [Greek: êlektron] au neutre,^1 mais aussi [Greek:
êlektros] au masculin^2 et même au féminin,^3 [Greek:
chrusêlektros],^4 [Greek: chrusophoros]^5 et peut-être, comme nous
l'avons vu, [Greek: chalkolithanon]; plus tard [Greek: souchion]^6 ou
[Greek: souchinos]^7, et [Greek: êlektrianos lithos];^8 plus tard
encore [Greek: berenikê], [Greek: beronikê] ou [Greek: bernikê];^9 il
s'est nommé [Greek: harpax] chez les Grecs établis en Syrie;^{10} chez
les Latins _succinum_, _electrum_, et deux variétés, _chryselectrum_ et
_sualiternicum_ {33} ou _subalternicum_;^{11} chez les Germains,
_Gless_;^{12} chez les Scythes, _sacrium_;^{13} chez les Egyptiens,
_sacal_;^{14} chez les Arabes, _karabé_^{15} ou _kahraba_;^{16} en
persan, _káruba_.^{17} Ce mot, qui appartient bien à la langue persane,
y signifie _attirant la paille_, et par conséquent exprime l'attraction
électrique, de même que le mot [Greek: harpax] des Grecs de Syrie. En
outre, le nom de _haur roumi_ (_peuplier romain_) était donné par les
Arabes, non-seulement à l'arbre dont ils croyaient que le succin était
la gomme, mais au succin lui-même. _Haur roumi_, transformé en _aurum_
par les traducteurs latins des auteurs arabes, et consondu mal à propos
avec _ambar_ ou _ambrum_, nom arabe latinisé de l'ambre gris, a produit
le nom moderne d'_ambre_, nom commun à l'_ambre jaune_ ou succin, qui
est une résine fossile, et à l'_ambre gris_, concrétion odorante qui se
forme dans les intestines des cachalots. On ne peut dire avec certitude
si le nom de basse grécité [Greek: bernikê] est la source ou le dérivé
de _Bern_, radical du nom allemand du succin (_Bernstein_). Quoi qu'il
en soit, le mot [Greek: bernikê] a produit _vernix_, nom d'une gomme
dans la basse latinité, d'où nous avons fait _vernis_.^{18}"
^1 Voyez Hérodote, III., 115; Platon, _Timée_, p. 80 c; Aristote,
_Météor._, IV., 10; Théophraste, _Hist. des plantes_, IX., 18 (19), §
2; _Des pierres_, § 28 et 29; Diodore de Sic., V., 23; Strabon, IV., 6,
n^o 2, p. 202 (Casaubon); Dioscoride, _Mat. méd._, I., 110; Plutarque,
_Questions de table_, II., 7, § 1; _Questions platoniques_, VII., 1 et
7; Lucien, _Du succin et des cygnes_; le même, _De Pastrologie_, § 19;
S. Clément, _Strom._ II., p. 370 (Paris, 1641, in-fol.); Alexandre
d'Aphr., _Quest. phys. et mor._, II., 23; Olympiodore, _Météor._, I.,
8, fol. 16, t. I., p. 197 (Ideler) et l'abréviateur d'Etienne de
Byzance au mot [Greek: Êlektrides].
^2 Voyez Sophocle, _Antigone_, v. 1038, et dans Eustathe, sur
l'_Iliade_, II., 865; Elien, _Nat. des animaux_, IV. 46; Quintus de
Smyrne, V., 623; Eustathe, sur la _Périégèse_ de Denys, p. 142
(Bernhardy), et sur l'_Odyssée_, IV., 73; et Suidas au mot [Greek:
hualê].
^3 Voyez Alexandre, _Problèmes_, sect. 1, prooem., p. 4 (Ideler);
Eustathe, sur l'_Odyssée_, IV., 73, et Tzetzès, _Chiliade_ VI., 650.
^4 Voyez Psellus, _Des pierres_, p. 36 (Bernard et Maussac).
^5 Voyez Dioscoride, _Mat. méd._, I., 110.
^6 Voyez S. Clément, _Strom._, II., p. 370 (Paris, 1641, in-fol.). Il
paraît distinguer l'un de l'autre [Greek: to souchion] et [Greek: to
êlektron], probablement parce qu'il attribue à tort au métal [Greek:
êlektron] la propriété attractive du succin.
^7 Voyez le faux Zoroastre, dans les _Géoponiques_, XV., 1, § 29.
^8 Voyez le faux Zoroastre, au même endroit.
^9 Voyez Eustathe, sur l'_Odyssée_, IV., 73; Tzetzès, _Chil._ VI., 650;
Nicolas Myrepse, _Antidotes_, ch. 327, et l'Etymol. Gud. au mot [Greek:
êlektron]. Comparez Saumaise, Exert. plin., p. 778.
^{10} Voyez Pline, XXXVII., 2, s. 11, n^o 37.
^{11} Voyez Pline, XXXVII., 2, s. 11-13, et Tacite, _Germanie_, ch. 45.
La forme _sualiternicum_, dans Pline (s. 11, n^o 33), est donnée par le
manuscrit de Bamberg et par M. Sillig (t. V., p. 390), au lieu de la
forme _subalternicum_ des éditions antérieures.
^{12} Voyez Tacite et Pline, _ll. cc._
^{13} Voyez Pline, XXXVII., 2, s. 11, n^o 40, Comp. J. Grimm, _Gesch.
der deutsch. Sprache_, Kap. x., p. 233 (Leipzig, 1848, in-8).
^{14} Pline, _l. c._
^{15} Voyez Saumaise, _De homon. hyles iatricæ_, c. 101, p. 162 (1689,
in-fol.).
^{16} Voyez Sprengel, sur Dioscoride, t. II., pp. 390-391.
^{17} Voyez M. de Sacy, cité par Buttmann, _Mythologus_, t. II., pp.
362-363.
^{18} Voyez Saumaise, _Ex. plin._, p. 778. Il n'est pas probable que le
mot [Greek: bernikê] ou [Greek: berenikê] nom du succin dans la grécité
du moyen âge, soit lié étymologiquement avec le nom propre [Greek:
berenikê], qui vient de l'adjectif macédonien [Greek: berenikos] pour
[Greek: pherenikos].
[110] PAGE 47, LINE 17. Page 47, line 20. _Mauri vero Carabem appellant,
quià solebant in sacrificijs, & deorum cultu ipsum libare. Carab enim
significat offerre Arabicè; ita Carabe, res oblata; aut rapiens paleas, vt
Scaliger ex Abohali citat, ex linguâ Arabicâ, vel Persicâ._--The printed
text, line 18, has "Non rapiens paleas," but in all copies of the folio of
1600, the "Non" has been altered in ink into "aut," possibly by Gilbert's
own hand. Nevertheless the editions of 1628 and 1633 both read "Non." There
appears to be no doubt that the origin of the word _Carabe_, or _Karabe_,
as assigned by Scaliger, is substantially correct. As shown in the
preceding note, Martin adopted this view. If any doubt should remain it
will be removed by the following notes which are due to Mr. A. Houtum
Schindler (member of the Institution of Electrical Engineers), of Terahan.
Reference is made to the magnetic and electric properties of stones in
three early Persian lapidaries. There are three stones only mentioned,
amber, loadstone, and garnet. The electric property of the diamond is not
mentioned. The following extracts are from the _Tansûk nâmah_, by Nasîr ed
dîn Tûsi, A.D. 1260. The two other treatises give the first extracts in the
same words.
"_Kâhrubâ_, also _Kahrabâ_ [Amber],
"Is yellow and transparent, and has its name from the property, which it
possesses, of attracting small, dry pieces of straw or grass, after it has
been rubbed with cloth and become warm. [Note. In Persian, Kâh = straw;
rubâ = the robber, hence Kâhrubâ = the straw-robber.] Some consider it a
mineral, and say that it is found in the Mediterranean and Caspian seas,
floating on the surface, but this is not correct. The truth is that Kâhrubâ
{34} is the gum of a tree, called jôz i rûmî [_i.e._, roman nut; walnut?],
and that most of it is brought from Rûm [here the Eastern Rome] and from
the confines of Sclavonia and Russia. On account of its bright colour and
transparency it is made into beads, rings, belt-buckles, &c. ... &c.
* * * * *
"The properties of attraction and repulsion are possessed by other
substances than loadstone, for instance, by amber and bîjâdah,^1 which
attract straws, feathers, etc., and of many other bodies, it can be said
that they possess the power of attraction. There is also a stone which
attracts gold; it has a pure yellow colour. There is also a stone which
attracts silver from distances of three or two yards. There are also the
stone which attracts tin, very hard, and smelling like asafoetida, the
stone attracting hair, the stone attracting meat, etc., but, latterly, no
one has seen these stones: no proof, however, that they do not exist."
Avicenna (Ibn Sinâ) gives the following under the heading of _Karabe_ (see
_Canona Medicinæ_, Giunta edition, Venet., 1608, lib. ii., cap. 371, p.
336):
"Karabe quid est? Gumma sicut sandaraca, tendens ad citrinitatem, &
albedinem, & peruietatem, & quandoque declinat ad rubedinem, quæ attrahit
paleas, & [fracturas] plantarum ad se, & propter hoc nominatur Karabe,
scilicet rapiens paleas, persicè.... Karabe confert tremori cordis, quum
bibitur ex eo medietas aurei cum aqua frigida, & prohibet sputum sanguinis
valde.... Retinet vomitum, & prohibet materias malas a stomacho, & cum
mastiche confortat stomachum.... Retinet fluxum sanguinis ex matrice, &
ano, & fluxum ventris, & confert tenasmoni."
Scaliger in _De Subtilitate_, _Exercitatio_ ciii., § 12, the passage
referred to by Gilbert says: "Succinum apud Arabas uocatur, Carabe: quod
princeps Aboali, rapiens paleas, interpretatur" (p. 163 _bis_, editio
Lutetiæ, 1557).
^1 _Bîjâdah_ is classified by Muhammad B. Mansûr (A.D. 1470) and by Ibn
al Mubârak (A.D. 1520) under "stones resembling ruby"; the Tansûk nâmah
describes it in a separate chapter. From the description it can be
identified with the almandine garnet, and the method of cutting this
stone _en cabochon_, with hollow back in order to display its colour
better is specially mentioned. The Tansûk nâmah only incidentally
refers to the electric property of the _bîjâdah_ in the chapter on
loadstone, but the other two treatises specially refer to it in their
description of the stone. The one has: "_Bîjâdah_ if rubbed until warm,
attracts straws and other light bodies just as amber does"; the other:
"_Bîjâdah_, if rubbed on the hair of the head, or on the beard,
attracts straws." Surûri, the lexicographer, who compiled a dictionary
in 1599, considers the _bîjâdah_ "a red ruby which possesses the
property of attraction." Other dictionaries do not mention the
attractive property, but some authors confound the stone with amber,
calling it _Kâbrubâ_, the straw-robber. The _bîjâdah_ is not rubellite
(red tourmaline) for it is described in the lapidaries as common,
whereas rubellite (from Ceylon) has always been rare, and was unknown
in Persia in the thirteenth century.
[111] PAGE 47, LINE 21. Page 47, line 25. _Succinum seu
succum._--Dioscorides regarded amber as the inspissated juice of the poplar
tree. From the Frankfurt edition of 1543 (_De Medicinali materia, etc._)
edited by Ruellius, we have, liber i., p. 53:
_Populus._ Cap. XCIII.
"... Lachrymam populorum commemorant quæ in Padum amnem defluat, durari, ac
coire in succinum, quod electrum vocant, alii chrysophorum. id attritu
jucundum odorem spirat, et aurum colore imitatur. tritum potumque stomachi
ventrisque fluxiones sistit."
To this Ruellius adds the commentary:
"Succinum seu succina gutta à succo dicta, Græcis [Greek: êlektrom] [sic],
esse {35} lachryma populi albæ, vel etiam nigræ quibusdam videtur, ab
ejusdem arboris resina. Dioscoridi et Galeno dicta differens et [Greek:
pterugophoros], id est paleas trahens, quoque vocatur, quantum ei quoque
Galenus tribuit li. 37, ca. 9. Succinum scribit à quibusdam pinei generis
arboribus, ut gummi à cerasis excidere autumno, et largum mitti ex Germania
septentrionali, et insulis maris Germanici. quod hodie nobis est
compertissimum: ad hæc liquata igni valentiore, quia à frigido intensiore
concrevit. pineam aperte olet, calidum primo gradu, siccum secundo,
stomachum roborat, vomitum, nauseam arcet. cordis palpitationi prodest.
pravorem humorum generationem prohibet.
"Germani weiss und gelbaugstein et bre[=n]stein.
"Galli ambra vocant: vulgo in corollis precariis frequens."
In the scholia of Johann Lonicer in his edition of Dioscorides, we find,
lib. i., cap. xcviii., _De nigra Populo_:
"[Greek: aigeiros], populus nigra ... idem electrum vel succinum [Greek:
haigeirou] lachrymam esse adseverat [Paulus], cui præter vires quæ ab
Dioscoride recensentur, tribuit etiam vim sistendi sanguinis, si tusum in
potu sumatur. Avicennæ Charabe, ut colligitur ex Joanne Jacobo Manlio, est
electrum hoc Dioscoridis, attestatur Brunfelsius. Lucianus planè nullum
electrum apud Eridanum seu Padum inveniri tradit, quandoquidem ne populus
quidem illa ab nautis ei demonstrari potuerit. Plinius rusticas
transpadanas ex electro monilia gestare adfirmat, quum à Venetis primum
agnoscere didicissent adversus nimirum vitia gutturis et tonsillarum. Num
sit purgamentum maris, vel lachryma populi, vel pinus, vel ex radiis
occidentis solis nascatur, vel ex montibus Sudinorum profluat, incertum
etiam Erasmus Stella relinquit. Sudinas tamen Borussiorum opes esse
constat."
Matthiolus (in _P. A. Mattioli ... Opera quæ extant omnia, hoc est
Commentarii in vi libros P. Dioscoridis de materia medica_, Frankfurt,
1596, p. 133) comments on the suggestion of Galen that amber came from the
_Populus alba_, and also comments on the Arabic, Greek, and Latin names of
amber.
The poplar-myth is commemorated by Addison (in _Italy_) in the lines:
No interwoven reeds a garland made,
To hide his brows within the vulgar shade;
But poplar wreathes around his temples spread,
And tears of amber trickled down his head.
Amber is, however, assuredly not derived from any poplar tree: it comes
from a species of pine long ago extinct, called by Göppert the _pinites
succinifer_.
Gilbert does not go into the medicinal uses, real or fancied, that have
been ascribed to amber in almost as great variety as to loadstone. Pliny
mentions some of these in his _Natural Historie_ (English version of 1601,
p. 609):
"He [Callistratus] saith of this yellow Amber, that if it be worne about
the necke in a collar, it cureth feavers, and healeth the diseases of the
mouth, throat, and jawes: reduced into pouder and tempered with honey and
oile of roses, it is soveraigne for the infirmities of the eares. Stamped
together with the best Atticke honey, it maketh a singular eyesalve for to
help a dim sight: pulverized, and the pouder thereof taken simply alone, or
else drunke in water with Masticke, is soveraigne for the maladies of the
stomacke."
Nicolaus Myrepsus (Recipe 951, _op. citat._) gives a prescription for {36}
dysentery and diabetes confiding chiefly of "Electri vel succi Nili (Nili
succum appellant Arabes Karabem)."
[112] PAGE 47, LINE 22. Page 47, line 26. _Sudauienses seu Sudini._--Cardan
in _De Rerum Varietate_, lib. iii., cap. xv. (Editio Basil., 1556, p. 152),
says of amber:
"Colligitur in quadam penè insula Sudinorum, qui nunc uoc[=a]tur Brusci, in
Prussia, nunc Borussia, juxta Veneticum sinum, & sunt orientaliores ostiis
Vistulæ fluuii: ubi triginta pagi huic muneri destinati sunt," etc. He
rejects the theory that it consists of hardened gum.
There exists an enormous literature concerning Amber and the Prussian amber
industry. Amongst the earliest works (after Theophrastus and Pliny) are
those of Aurifaber (_Bericht über Agtstein oder Börnstein_, Königsberg,
1551); Goebel (_De Succino, Libri duo, authore Severino Goebelio, Medico
Doctore_, Regiomont., 1558); and Wigand (_Vera historia de Succino
Borussico_, Jena, 1590). Later on Hartmann, P. J. (_Succini Prussici
Physica et civilis Historia_, Francofurti, 1677); and the splendid folio of
Nathaniel Sendel (_Historia Succinorum corpora aliena involventium_,
Lipsiæ, 1742), with its wealth of plates illustrating amber specimens, with
the various included fossil fauna and flora. Georgius Agricola (_De natura
Fossilium_, liber iv.), and Aldrovandi (_Musæeum Metallicum_, pp. 411-412)
must also be mentioned. Bibliographies of the earlier literature are to be
found in Hartmann (_op. citat._), and in Daniel Gralath, _Elektrische
Bibliothek_ (_Versuche und Abhandlungen der Naturforschenden Gesellschaft
in Danzig_, Zweiter Theil, pp. 537-539, Danzig and Leipzig, 1754). See also
Karl Müllenhoff, _Deutsche Altertumskunde_, vol. i., Zweites Buch, pp.
211-224, Zinn und Bernsteinhandel (Berlin, 1870), and Humboldt's _Cosmos_
(Bohn's edition, London, 1860, vol. ii., p. 493).
The ancient Greek myth according to which amber was the tears of the
Heliades, shed on the banks of the river Eridanus over Phaethon, is not
alluded to by Gilbert. It is narrated in well-known passages in Ovid and in
Hyginus. Those interested in the modern handling of the myth should refer
to Müllenhoff (_op. citat._, pp. 217-223, der Bernsteinmythus), or to that
delightful work _The Tears of the Heliades_, by W. Arnold Buffum (London,
1896).
[113] PAGE 47, LINE 30. Page 47, line 36. _quare & muscos ... in frustulis
quibusdam comprehensos retinet._--The occurrence of flies in amber was well
known to the ancients. Pliny thus speaks of it, book xxxvii., chap. iii.
(p. 608 of P. Holland's translation of 1601):
"That it doth destill and drop at the first very clear and liquid, it is
evident by this argument, for that a man may see diverse things within, to
wit, Pismires, Gnats, and Lizards, which no doubt were entangled and stucke
within it when it was greene and fresh, and so remain enclosed within as it
waxed harder."
A locust embedded in amber is mentioned in the _Musæum Septalianum_ of
Terzagus (Dertonæ, 1664).
Martial's epigram (_Epigrammata_, liber vi., 15) is well known:
Dum Phaethontea formica vagatur in umbra
Implicuit tenuem succina gutta feram.
See also Hermann (Daniel), _De rana et lacerta Succino Borussiaco insitis_
{37} (Cracov., 1580; a later edition, Rigæ, 1600). The great work on
_inclusa_ in amber is, however, that of Nathaniel Sendel. See the previous
note.
Sir Thomas Browne must not be forgotten in this connexion. The
_Pseudodoxia_ (p. 64 of the second edition, 1650) says:
"Lastly, we will not omit what Bellabonus upon his own experiment writ from
Dantzich unto Mellichius, as he hath left recorded in his chapter _De
Succino_, that the bodies of Flies, Pismires and the like, which are said
oft times to be included in Amber, are not reall but representative, as he
discovered in severall pieces broke for that purpose. If so, the two famous
Epigrams hereof in Martiall are but poeticall, the Pismire of Brassavolus
Imaginary, and Cardans Mousoleum for a flie, a meer phancy. But hereunto we
know not how to assent, as having met with some whose reals made good their
representments." See also Pope's _Epistle to Dr. Arbuthnot_, line 169.
[114] PAGE 47, LINE 34. Page 47, line 40. _Commemorant antiqui quod
succinum festucas et paleas attrahit._--Pliny (book xxxvii., chap. ii., p.
606 of the English edition of 1601) thus narrates the point:
"Hee [_Niceas_] writeth also, that in Aegypt it [amber] is engendered....
Semblably in Syria, the women (saith hee) make wherves of it for their
spindles, where they use to call it Harpax, because it will catch up
leaves, straws, and fringes hanging to cloaths."
p. 608. "To come to the properties that Amber hath, If it bee well rubbed
and chaufed betweene the fingers, the potentiall facultie that lieth
within, is set on work, and brought into actual operation, whereby you
shall see it to drawe chaffe strawes, drie leaves, yea, and thin rinds of
the Linden or Tillet tree, after the same sort as loadstone draweth yron."
[115] PAGE 47, LINE 36. Page 47, line 42. _Quod etiam facit Gagates
lapis._--The properties of Jet were well known to the mediæval writers.
_Julius Solinus_ writes in _De Mirabilibus_, chapter xxxiv., _Of Britaine_
(English version of 1587 by A. Golding):
"Moreover to the intent to passe the large aboundance of sundry mettals
(whereof Britaine hath many rich mynes on all sides), Here is store of the
stone called Geate, and y^e best kind of it. If ye demaund y^e beautie of
it, it is a black Jewell: if the qualitie, it is of no weight: if the
nature, it burneth in water, and goeth out in Oyle; if the power, rubbe it
till it be warme, and it holdeth such things as are laide to it; as Amber
doth. The Realme is partlie inhabited of barbarous people, who even frõ
theyr childhoode haue shapes of divers beastes cunninglye impressed and
incorporate in theyr bodyes, so that beeing engraued as it were in theyr
bowels, as the man groweth, so growe the marks painted vpon him...."
Pliny describes it as follows (p. 589, English edition of 1601):
"The Geat, which otherwise we call Gagates, carrieth the name of a toune
and river both in Lycia, called Gages: it is said also, that the sea
casteth it up at a full tide or high water into the Island Leucola, where
it is gathered within the space of twelve stadia, and no where else: blacke
it is, plaine and even, of a hollow substance in manner of the pumish
stone, not much differing from the nature of wood; light, brittle, and if
it bee rubbed or bruised, of a strong flavour." (Book xxxvi., chap. xviii.)
In the Commentary of Joannes Ruellius upon Dioscorides, _Pedanii
Dioscoridis Anazarbei de medicinali materia libri sex, Ioanne Ruellio
Suessionensi interprete_ ... (Frankfurt, 1543, fol., liber quintus, cap.
xcii.) is the following description:
{38} "In Gagatarum lapidum genere, præferendus qui celeriter accenditur, et
odorem bituminis reddit. niger est plerunque, et squalidus, crustosus, per
quam levis. Vis ei molliendi, et discutiendi. deprehendit sonticum morbum
suffitus, recreatque uuluæ strangulationes. fugat serpentes nidore.
podagricis medicaminibus, et a copis additur. In Cilicia nasci solet, qua
influens amnis in mare effunditur, proxime oppidum quod Plagiopolis
dicitur. vocatur autem et locus et amnis Gagas, in cujus faucibus ii
lapides inveniuntur.
"Gagates lapis colore atro, Germanis Schwartzer augstein, voce parum
depravata, dicitur. odore dum uritur bituminis, siccat, glutinat, digerit
admotus, in corollis precariis et salinis frequens."
And in the _Scholia_ upon Dioscorides of Joannes Lonicer (Marpurgi, 1643,
cap. xcvii., p. 80) is the following:
"_De Gagate Lapide._ Ab natali solo, urbe nimirum Gagae Lyciae nomen habet.
Galenus se flumen isthuc et lapidem non invenisse, etiamsi naui parua totam
Lyciam perlustravit: ait, se autem in caua Syria multos nigros lapides
invenisse glebosos, qui igni impositi, exiguam flammam gignerent. Meminit
hujus Nicander in Theriacis nempe suffitum hujus abigere venenata."
There is also a good account of _Gagates_ (and of Succinum) by Langius,
_Epistola_ LXXV., p. 454, of the work _Epistolarum medicinalium volumen
tripartitum_ (Francofurti, 1589).
[116] PAGE 47, LINE 39. Page 47, line 45. _Multi sunt authores
moderni._--The modern authors who raised Gilbert's wrath by ignorantly
copying out all the old tales about amber, jet, and loadstone, instead of
investigating the facts, were, as he says at the beginning of the chapter,
some theologians, and some physicians. He seems to have taken a special
dislike to Albertus Magnus, to Puteanus (Du Puys), and to Levinus Lemnius.
[117] PAGE 47, LINE 39. Page 47, line 46. _& gagate._--The editions of 1628
and 1633 both read _ex gagate_.
[118] PAGE 48, LINE 14. Page 48, line 16. _Nam non solum succinum, &
gagates (vt illi putant) allectant corpuscula._--The list of bodies known
to become electrical by friction was not quite so restricted as would
appear from this passage. Five, if not six, other minerals had been named
in addition to amber and jet.
(1.) _Lyncurium._ This stone, about which there has been more obscurity and
confusion than about any other gem, is supposed by some writers to be the
tourmaline, by others a jacinth, and by others a belemnite. The ancients
supposed it to be produced from the urine of the lynx. The following is the
account of Theophrastus, _Theophrastus's History of Stones. With an English
Version_ ..., by "Sir" John Hill, London, 1774, p. 123, ch. xlix.-l. "There
is some Workmanship required to bring the Emerald to its Lustre, for
originally it is not so bright. It is, however, excellent in its Virtues,
as is also the _Lapis Lyncurius_, which is likewise used for engraving
Seals on, and is of a very solid Texture, as Stones are; it has also an
attractive Power, like that of Amber, and is said to attract not only
Straws and small pieces of Sticks, but even Copper and Iron, if they are
beaten to thin pieces. This Diocles affirms. The _Lapis Lyncurius_ is
pellucid, and of a fire Colour." See also W. Watson in _Philos. Trans._,
1759, L. i., p. 394, _Observations concerning the Lyncurium of the
ancients_.
(2.) _Ruby._
(3.) _Garnet._ The authority for both these is Pliny, _Nat. Hist._, book
xxxvii., chap. vii. (p. 617 of English edition of 1601).
{39} "Over and besides, I find other sorts of Rubies different from those
above-named;... which being chaufed in the Sun, or otherwise set in a heat
by rubbing with the fingers, will draw unto them chaffe, strawes, shreads,
and leaves of paper. The common Grenat also of Carchedon or Carthage, is
said to doe as much, although it be inferiour in price to the former."
(4.) _Jasper._ Affaytatus is the authority, in _Fortunii Affaitati Physici
atque Theologi ... Physicæ & Astronomicæ c[=o]siderationes_ (Venet., 1549),
where, on p. 20, he speaks of the magnet turning to the pole, likening it
to the turning of a "palea ab Ambro vel Iaspide et hujuscemodi lapillis
lucidis."
(5.) _Lychnis._ Pliny and St. Isidore speak of a certain stone _lychnis_,
of a scarlet or flame colour, which, when warmed by the sun or between the
fingers, attracts straws or leaves of papyrus. Pliny puts this stone
amongst carbuncles, but it is much more probably _rubellite_, that is to
say, red tourmaline.
(6.) _Diamond._ In spite of the confusion already noted, _à propos_ of
_adamas_ (Note to p. 47), between loadstone and diamond, there seems to be
one distinct record of an attractive effect having been observed with a
rubbed diamond. This was recorded by Fracastorio, _De sympathia et
antipathia rerum_ (Giunta edition, Venice, MDLXXIIII, chap. v., p. 60
_verso_), "cujus rei & illud esse signum potest, cum confricata quædã vt
Succinum, & Adamas fortius furculos trahunt." And (on p. 62 _recto_); "nam
si per similitudine (vt supra diximus) fit hæc attractio, cur magnes non
potius magnetem trahit, [~q] ferrum, & ferrum non potius ad ferrum movetur,
quàm ad magnetem? quæ nam affinitas est pilorum, & furculorum cum Electro,
& Adamante? præsertim [~q] si cum Electro affines sunt, quomodo & cum
Adamante affinitatem habebunt, qui dissimilis Electro est?" An
incontestable case of the observation of the electrification of the diamond
occurs in Gartias ab Horto. The first edition of his _Historia dei Semplici
Aromati_ was publisht at Goa in India in 1563. In chapter xlviii. on the
Diamond, occur these words (p. 200 of the Venetian edition of 1616):
"Questo si bene ho sperimentato io più volte, che due Diamanti perfetti
fregati insieme, si vniscono di modo insieme, che non di leggiero li potrai
separare. Et ho parimente veduto il Diamante dopo di esser ben riscaldato,
tirare à se le festuche, non men, che si faccia l'elettro." See also
Aldrovandi, _Musæum Metallicum_ (Bonon., 1648, p. 947).
Levinus Lemnius also mentions the Diamond along with amber. See his
_Occulta naturæ miracula_ (English edition, London, 1658, p. 199).
[119] PAGE 48, LINE 16. Page 48, line 18. _Iris gemma._--The name _iris_
was given, there can be little doubt, to clear six sided prisms of
rock-crystal (quartz), which, when held in the sun's beams, cast a crude
spectrum of the colours of the rainbow. The following is the account of it
given in Pliny, book xxxvii., chap. vii. (p. 623 of the English version of
1601):
"... there is a stone in name called Iris: digged out of the ground it is
in a certaine Island of the red sea, distant from the city Berenice three
score miles. For the most part it resembleth Crystall: which is the reason
that some hath tearmed it the root of Crystall. But the cause why they call
it Iris, is, That if the beames of the Sunne strike upon it directly within
house, it doth send from it against the walls that bee neare, the very
resemblance both in forme and also in colour of a rainebow; and eftsoones
it will chaunge the same in much varietie, to the great admiration of them
that behold it. For certain it is knowne, that six angles it hath in manner
of the Crystall: but they say that some of them have their sides rugged,
and the same {40} unequally angled: which if they be laid abroad against
the Sunne in the open aire, do scatter the beames of the Sunne, which light
upon them too and fro: also that others doe yeeld a brightnes from
themselves, and thereby illuminat all that is about them. As for the
diverse colours which they cast forth, it never happeneth but in a darke or
shaddowie place: whereby a man may know, that the varietie of colours is
not in the stone Iris, but commeth by the reverberation of the wals. But
the best Iris is that which representeth the greatest circles upon the
wall, and those which bee likest unto rainebowes indeed."
In the English translation of Solinus's _De Mirabilibus_ (_The excellent
and pleasant worke of Julius Solinus containing the noble actions of
humaine creatures, the secretes and providence of nature, the descriptions
of countries ... tr. by A. Golding, gent._, Lond., 1587), chapter xv. on
Arabia has the following:
"Hee findeth likewise the Iris in the Red sea, sixe cornered as the
Crystall: which beeing touched with the Sunnebeames, casteth out of him a
bryght reflexion of the ayre like the Raynebowe."
Iris is also mentioned by Albertus Magnus (_De mineralibus_, Venet., 1542,
p. 189), by Marbodeus Gallus (_De lapidibus_, Par. 1531, p. 78), who
describes it as "crystallo simulem sexangulam," by Lomatius (_Artes of
curious Paintinge_, Haydocke's translation, Lond., 1598, p. 157), who says,
"... the Sunne, which casting his beames vpon the _stone Iris_, causeth the
_raine-bowe_ to appeare therein ...," and by "Sir" John Hill (_A General
Natural History_, Lond., 1748, p. 179).
Figures of the Iris given by Aldrovandi in the _Musæum Metallicum_ clearly
depict crystals of quartz.
[120] PAGE 48, LINE 16. Page 48, line 18. _Vincentina, & Bristolla (Anglica
gemma siue fluor)_. This is doubtless the same substance as the _Gemma
Vincentij rupis_ mentioned on p. 54, line 16 (p. 54, line 18, of English
Version), and is nothing else than the so-called "Bristol diamond," a
variety of dark quartz crystallized in small brilliant crystals upon a
basis of hæmatite. To the work by Dr. Thomas Venner (Lond., 1650), entitled
_Via Recta_ or the _Bathes of Bathe_, there is added an appendix, _A
Censure concerning the water of Saint Vincents Rocks neer Bristol (Urbs
pulchra et Emporium celebre)_, in which, at p. 376, occurs this passage:
"This Water of Saint _Vincents_ Rock is of a very pure, cleare, crystalline
substance, answering to those crystalline Diamonds and transparent stones
that are plentifully found in those Clifts."
In the _Fossils Arranged_ of "Sir" John Hill (Lond., 1771), p. 123, is the
following entry: "Black crystal. Small very hard heavy glossy. Perfectly
black, opake. Bristol (grottos, glass)" referring to its use.
The name _Vincentina_ is not known as occurring in any mineralogical book.
Prof. H. A. Miers, F.R.S., writes concerning the passage: "_Anglica gemma
sive fluor_ seems to be a synonym for _Bristolla_, or possibly for
_Vincentina et Bristolla_. Both quartz and fluor are found at Clifton. In
that case Vincentina and Bristolla refer to these two minerals, and if so
one would expect Bristolla to be the Bristol Diamond, and Vincentina to be
the comparatively rare Fluor spar from that locality."
At the end of the edition of 1653 of Sir Hugh Plat's _Jewel House of Art
and Nature_, is appended _A rare and excellent Discourse of Minerals,
Stones, Gums, and Rosins; with the vertues and use thereof_, By D. B.
_Gent_. Here, p. 218, we read:
"We have in England a stone or mineral called a Bristol stone (because {41}
many are found thereabouts) which much resembles the Adamant or Diamond,
which is brought out of Arabia and Cyprus; but as it is wanting of the same
hardnesse, so falls it short of the like vertues."
[121] PAGE 48, LINE 18. Page 48, line 19. _Crystallus._--Rock-crystal.
Quartz. Pliny's account of it (Philemon Holland's version of 1601, p. 604)
in book xxxvii., chap, ii., is:
"As touching Crystall, it proceedeth of a contrarie cause, namely of cold;
for a liquor it is congealed by extreame frost in manner of yce; and for
proofe hereof, you shall find crystall in no place els but where the winter
snow is frozen hard: so as we may boldly say, it is verie yce and nothing
else, whereupon the Greeks have give it the right name Crystallos, _i._
Yce.... Thus much I dare my selfe avouch, that crystall groweth within
certaine rockes upon the Alps, and these so steepe and inaccessible, that
for the most part they are constrained to hang by ropes that shall get it
forth."
[122] PAGE 48, LINE 18. Page 48, line 20. _Similes etiam attrahendi vires
habere videntur vitrum ... sulphur, mastix, & cera dura sigillaris._ If, as
shown above, the electric powers of diamond and ruby had already been
observed, yet Gilbert was the first beyond question to extend the list of
_electrics_ beyond the class of precious stones, and his discovery that
_glass_, _sulphur_, and _sealing-wax_ acted, when rubbed, like amber, was
of capital importance. Though he did not pursue the discovery into
mechanical contrivances, he left the means of that extension to his
followers. To Otto von Guericke we owe the application of sulphur to make
the first electrical machine out of a revolving globe; to Sir Isaac Newton
the suggestion of glass as affording a more mechanical construction.
Electrical attraction by natural products other than amber after they have
been rubbed must have been observed by the primitive races of mankind.
Indeed Humboldt in his _Cosmos_ (Lond., 1860, vol. i., p. 182) records a
striking instance:
"I observed with astonishment, on the woody banks of the Orinoco, in the
sports of the natives, that the excitement of electricity by friction was
known to these savage races, who occupy the very lowest place in the scale
of humanity. Children may be seen to rub the dry, flat and shining seeds or
husks of a trailing plant (probably a _Negretia_) until they are able to
attract threads of cotton and pieces of bamboo cane."
[123] PAGE 48, LINE 23. Page 48, line 25. _arsenicum_.--This is _orpiment_.
See the _Dictionary of metallick words_ at the end of Pettus's _Fleta
Minor_.
[124] PAGE 48, LINE 23. Page 48, line 26. _in convenienti coelo
sicco_.--The observation that only in a dry climate do rock-salt, mica, and
rock-alum act as electrics is also of capital importance. Compare page 56.
[125] PAGE 48, LINE 27. Page 48, line 31. _Alliciunt hæc omnia non festucas
modo & paleas._--Gilbert himself marks the importance of this discovery by
the large asterisk in the margin. The logical consequence was his invention
of the first _electroscope_, the _versorium non magneticum_, made of any
metal, figured on p. 49.
[126] PAGE 48, LINE 34. Page 48, line 36. _quod tantum siccas attrahat
paleas, nec folia ocimi._--This silly tale that basil leaves were not
attracted by amber arose in the _Quæstiones Convivales_ of Plutarch. It is
repeated by Marbodeus and was quoted by Levinus Lemnius as true. Gilbert
denounced it as nonsense. Cardan (_De Subtilitate_, Norimb., 1550, p. 132)
had already contradicted the fable. "Trahit enim," he says, "omnia levia,
paleas, festucas, ramenta {42} tenuia metallorum, & ocimi folia, perperam
contradicente Theophrasto." Sir Thomas Browne specifically refuted it. "For
if," he says, "the leaves thereof or dried stalks be stripped into small
strawes, they arise unto Amber, Wax, and other Electricks, no otherwise
then those of Wheat or Rye."
[127] PAGE 48, LINE 34. Page 48, line 38. _Sed vt poteris manifestè
experiri...._
Gilbert's experimental discoveries in electricity may be summarized as
follows:
1. The generalization of the class of _Electrics_.
2. The observation that damp weather hinders electrification.
3. The generalization that electrified bodies attract everything,
including even metals, water, and oil.
4. The invention of the non-magnetic _versorium_ or electroscope.
5. The observation that merely warming amber does not electrify it.
6. The recognition of a definite class of _non-electrics_.
7. The observation that certain electrics do not attract if roasted or
burnt.
8. That certain electrics when softened by heat lose their power.
9. That the electric effluvia are stopped by the interposition of a
sheet
of paper or a piece of linen, or by moist air blown from the mouth.
10. That glowing bodies, such as a live coal, brought near excited amber
discharge its power.
11. That the heat of the sun, even when concentrated by a burning mirror,
confers no vigour on the amber, but dissipates the effluvia.
12. That sulphur and shell-lac when aflame are not electric.
13. That polish is not essential for an electric.
14. That the electric attracts bodies themselves, not the intervening
air.
15. That flame is not attracted.
16. That flame destroys the electrical effluvia.
17. That during south winds and in damp weather, glass and crystal, which
collect moisture on their surface, are electrically more interfered
with than amber, jet and sulphur, which do not so easily take up
moisture on their surfaces.
18. That pure oil does not hinder production of electrification or
exercise
of attraction.
19. That smoke is electrically attracted, unless too rare.
20. That the attraction by an electric is in a straight line toward it.
[128] PAGE 48, LINE 35. Page 48, line 39. _quæ sunt illæ
materiæ._--Gilbert's list of electrics should be compared with those given
subsequently by Cabeus (1629), by Sir Thomas Browne (1646), and by Bacon.
The last-named list occurs in his _Physiological Remains_, published
posthumously in 1679; it contains nothing new. Sir Thomas Browne's list is
given in the following passage, which is interesting as using for the first
time in the English language the noun _Electricities_:
"Many stones also both precious and vulgar, although terse and smooth, have
not this power attractive; as Emeralds, Pearle, Jaspis, Corneleans, Agathe,
Heliotropes, Marble, Alablaster, Touchstone, Flint and Bezoar. Glasse
attracts but weakely though cleere, some slick stones and thick glasses
indifferently: Arsenic but weakely, so likewise glasse of Antimony, but
Crocus Metallorum not at all. Saltes generally but weakely, as Sal Gemma,
Alum, and also Talke, nor very discoverably by any frication: but if gently
warmed at the fire, and wiped with a dry cloth, they will better discover
their Electricities." _(Pseudodoxia Epidemica_, p. 79.)
In the _Philosophical Transactions_, vol. xx., p. 384, is _A Catalogue of
Electrical Bodies_ by the late Dr. Rob. Plot. It begins "Non solum
succinum," and ends "alumen rupeum," being identical with Gilbert's list
except that he calls "Vincentina & Bristolla" by the name "Pseudoadamas
Bristoliensis."
[129] PAGE 49, LINE 25. Page 49, line 30. _non dissimili modo._--The
_modus_ {43} _operandi_ of the electrical attractions was a subject of much
discussion; see Cardan, _op. citat._
[130] PAGE 51, LINE 2. Page 51, line 1. _appellunt._--This appears to be a
misprint for _appelluntur_.
[131] PAGE 51, LINE 22. Page 51, line 23. _smyris._--Emery. This substance
is mentioned on p. 22 as a magnetic body.
[132] PAGE 52, LINE 1. Page 51, line 46. _gemmæ ... vt Crystallus, quæ ex
limpidâ concreuit._ See the note to p. 48.
[133] PAGE 52, LINE 30. Page 52, line 32. _ammoniacum._--Ammoniacum, or
Gutta Ammoniaca, is described by Dioscorides as being the juice of a ferula
grown in Africa, resembling galbanum, and used for incense.
"_Ammoniack_ is a kind of Gum like Frankincense; it grows in Lybia, where
_Ammon's_ Temple was." Sir Hugh Plat's _Jewel House of Art and Nature_ (Ed.
1653, p. 223).
[134] PAGE 52, LINE 38. Page 52, line 41. _duæ propositæ sunt causæ ...
materia & forma._--Gilbert had imbibed the schoolmen's ideas as to the
relations of matter and form. He had discovered and noted that in the
magnetic attractions there was always a verticity, and that in the
electrical attractions the rubbed electrical body had no verticity. To
account for these differences he drew the inference that since (as he had
satisfied himself) the magnetic actions were due to _form_, that is to say
to something immaterial--to an "imponderable" as in the subsequent age it
was called--the electrical actions must necessarily be due to _matter_. He
therefore put forward his idea that a substance to be an electric must
necessarily consist of a concreted humour which is partially resolved into
an effluvium by attrition. His discoveries that electric actions would not
pass through flame, whilst magnetic actions would, and that electric
actions could be screened off by interposing the thinnest layer of fabric
such as sarcenet, whilst magnetic actions would penetrate thick slabs of
every material except iron only, doubtless confirmed him in attributing the
electric forces to the presence of these effluvia. See also p. 65. There
arose a fashion, which lasted over a century, for ascribing to "humours,"
or "fluids," or "effluvia," physical effects which could not otherwise be
accounted for. Boyle's tracts of the years 1673 and 1674 on "effluviums,"
their "determinate nature," their "strange subtilty," and their "great
efficacy," are examples.
[135] PAGE 53, LINE 9. Page 53, line 11. _Magnes vero...._--This passage
from line 9 to line 24 states very clearly the differences to be observed
between the magnetical and the electrical attractions.
[136] PAGE 53, LINE 36. Page 53, line 41. _succino calefacto._--Ed. 1633
reads _succinum_ in error.
[137] PAGE 54, LINE 9. Page 54, line 11. _Plutarchus ... in quæstionibus
Platonicis._--The following Latin version of the paragraph in _Quæstio
sexta_ is taken from the bilingual edition publisht at Venice in 1552, p.
17 _verso_, liber vii., cap. 7 (or, _Quæstio Septima_ in Ed. Didot, p.
1230).
"Electrum uero quæ apposita sunt, nequaquàm trahit, quem admodum nec lapis
ille, qui sideritis nuncupatur, nec quicqu[=a] à seipso ad ea quæ in
propinquo sunt, extrinsecus assilit. Verum lapis magnes effluxiones quasdam
tum graves, tum etiam spiritales emittit, quibus aer continuatus & iunctus
repellitur. Is deinceps alium sibi proximum impellit, qui in orbem circum
actus, atque ad inanem locum rediens, ui ferrum fecum rapit & trahit. At
Electrum uim quandam flammæ similem & spiritalem continet, quam quidem {44}
tritu summæ partis, quo aperiuntur meatus, foras eijcit. Nam leuissima
corpuscula & aridissima quæ propè sunt, sua tenuitate atque imbecillitate
ad seipsum ducit & rapit, cum non sit adeo ualens, nec tantum habeat
ponderis & momenti ad expellendam aeris copiam, ut maiora corpora more
Magnetis superare possit & uincere."
[138] PAGE 54, LINE 16. Page 54, line 18. _Gemma Vincentij rupis._--See the
note to p. 48 _supra_, where the name _Vincentina_ occurs.
[139] PAGE 54, LINE 30. Page 54, line 35. _orobi._--The editions of 1628
and 1633 read _oribi_.
[140] PAGE 55, LINE 34. Page 55, line 42. _in euacuati._--The editions of
1628 and 1633 read _inevacuati_.
[141] PAGE 58, LINE 21. Page 58, line 25. _assurgentem vndam ... declinat
ab F._--These words are wanting in the Stettin editions.
[142] PAGE 59, LINE 9. Page 59, line 9. _fluore._--This word is conjectured
to be a misprint for _fluxu_ but it stands in all editions.
[143] PAGE 59, LINE 22. Page 59, line 25. _Ruunt ad electria._--This
appears to be a slip for _electrica_, which is the reading of the editions
of 1628 and 1633.
[144] PAGE 60, LINE 7. Page 60, line 9. _tan[=q] materiales radij._--The
suggestion here of material _rays_ as the _modus operandi_ of electric
forces seems to foreshadow the notion of electric lines of force.
[145] PAGE 60, LINE 10. Page 60, line 12. _Differentia inter magnetica &
electrica._--Though Gilbert was the first systematically to explore the
differences that exist between the magnetic attraction of iron and the
electric attraction of all light substances, the point had not passed
unheeded, for we find St. Augustine, in the _De Civitate Dei_, liber xxi.,
cap. 6, raising the question why the loadstone which attracts iron should
refuse to move straws. The many analogies between electric and magnetic
phenomena had led many experimenters to speculate on the possibility of
some connexion between electricity and magnetism. See, for example,
Tiberius Cavallo, _A Treatise on Magnetism_, London, 1787, p. 126. Also the
three volumes of J. H. van Swinden, _Receuil de Mémoires sur l'Analogie de
Electricité et du Magnétisme_, La Haye, 1784. Aepinus wrote a treatise on
the subject, entitled _De Similitudine vis electricæ et magneticæ_
(Petropolis, 1758). This was, of course, long prior to the discovery, by
Oersted, in 1820, of the real connexion between magnetism and the electric
current.
[146] PAGE 60, LINE 25. Page 60, line 31. _Coitionem dicimus, non
attractionem._--See the remarks, at the outset of these Notes, on Gilbert's
definitions of words.
[147] PAGE 60, LINE 33. Page 61, line 1. _Orpheus in suis
carminibus._--This passage is in the chapter [Greek: Lithika] of Orpheus,
verses 301 to 327. See Note to p. 11, line 19.
[148] PAGE 61, LINE 15. Page 61, line 19. _Platonis in Timæo opinio_.--The
passage runs (edition Didot, vol. ii., p. 240, or Stephanus, p. 80, C.):
[Greek: Kai dê kai ta tôn hudatôn panta rheumata eti de ta tôn keraunôn
ptômata kai ta thaumazomena êlektrôn peri tês helxeôs kai tôn Hêrakleiôn
lithôn, pantôn toutôn holkê men ouk estin oudeni pote, to de kenon einai
mêden periôthein te hauta tauta eis allêla, to te diakrinomena kai
sunkrinomena pros tên hautôn diameibomena hedran hekasta ienai panta,
toutois tois pathêmasi pros allêla sumplechtheisi tethaumatourgêmena tôi
kata tropon zêtounti phanêsetai.]
[149] PAGE 61, LINE 30. Page 61, line 38. The English version of the lines
of Lucretius is from Busby's translation.
[150] PAGE 62, LINE 5. {45} Page 62, line 7. _Iohannes Costæus
Laudensis._--Joannes Costa, of Lodi, edited Galen and Avicenna. He also
wrote a _De universali stirpium Natura_ (Aug. Taurin., 1578).
[151] PAGE 63, LINE 3. Page 63, line 4. _Cornelius Gemma 10.
Cosmocrit._--This refers to the work _De Naturæ Divinis Characterismis ...
Libri ii. Avctore D. Corn. Gemma_ (Antv., 1575, lib. i., cap. vii., p.
123).
"Certè vt à magnete insensiles radij ferrum ad se attrahunt, ab echineide
paruo pisciculo sistuntur plena nauigia, à catoblepa spiritu non homines
solùm, sed & alta serpentum genera interimuntur, & saxa dehiscunt."
See also Kircher's _Magneticum Naturæ Regnum_ (Amsterodami, 1667, p. 172),
Sectio iv., cap. iii., De Magnete Navium, quæ Remora seu Echeneis dicitur.
See the note to p. 7, line 21.
[152] PAGE 63, LINE 6. Page 63, line 7. _Guilielmus Puteanus._--Puteanus
(Du Puys) wrote a work _De Medicamentorum quomodocunque Purgantium
Facultatibus_, Libri ii. (Lugd., 1552), in which he talks vaguely about the
substantial "form" of the magnet, and quotes Aristotle and Galen.
[153] PAGE 63, LINE 21. Page 63, line 25. _Baptistæ Portæ._--The passage in
the translation is quoted from the English version of 1658, pp. 191, 192.
[154] PAGE 64, LINE 4. Page 64, line 9. _Eruditè magis Scaliger._--Gilbert
pokes fun at Scaliger, whose "erudite" guess (that the motion of iron to
the magnet was that of the offspring toward the parent) is to be found in
his book _De Subtilitate, ad Cardanum_, Exercitatio CII. (Lutetiæ, 1557, p.
156 _bis_).
[155] PAGE 64, LINE 7. Page 64, line 11. _Diuus Thomas._--On p. 3 Gilbert
had already spoken of St. Thomas Aquinas as a man of intellect who would
have added more about the magnet had he been more conversant with
experiments. The passage here quoted is from the middle of Liber vii. of
his commentaries on the _de Physica_ of Aristotle, _Expositio Diui Thome
Aquinatis Doctoris Angelici super octo libros Physicorum Aristotelis_, etc.
(Venice, Giunta edition, 1539, p. 96 _verso_, col. 2).
[156] PAGE 64, LINE 16. Page 64, line 24. _Cardinalis etiam
Cusanus._--Cardinal de Cusa (Nicolas Khrypffs) wrote a set of dialogues on
Statics, _Nicolai Cusani de staticis experimentis dialogus_ (1550), of
which an English version appeared in London in 1650 with the title, _The
Idiot in four books; the first and second of wisdom, the third of the
minde, the fourth of statick experiments. By the famous and learned C.
Cusanus._ In the fourth book _of statick Experiments, Or experiments of the
Ballance_, occurs (p. 186) the following:
"_Orat._ Tell me, if thou hast any device whereby the vertues of stones
may be weighed.
"_Id._ I thinke the vertue of the Load-stone might be weighed, if
putting some Iron in one scale, and a Load-stone in the other, untill
the ballance were even, then taking away the Load-stone, and some other
thing of the same weight being put into the scale, the Load-stone were
holden over the Iron, so that that scale wou'd begin to rise; by reason
of the Load-stones attraction of the Iron, then take out some of the
weight of the other scale, untill the scale wherein the iron is, doe
sinke againe to the æquilibrium, or equality still holding the
Load-stone unmovable as it was; I beleeve that by weight of what was
taken out of the contrary scale, one might come proportionably to the
weight of the vertue or power of the Load-stone. And in like manner,
the vertue of a Diamond, might be found hereby, because {46} they say
it hinders the Load-stone from drawing of Iron; and so other vertues of
other stones, consideration, being alwayes had of the greatnesse of the
bodyes, because in a greater body, there is a greater power and
vertue."
In the 1588 edition of Baptista Porta's _Magiæ Naturalis Libri xx._, in
lib. vii., cap. xviii., occurs the description of the use of the balance to
which Gilbert refers.
[157] PAGE 67, LINE 21. Page 67, line 22. _aëris rigore._--All editions
read thus, but the sense seems to require _frigore_.
[158] PAGE 67, LINE 27. Page 67, line 31. _Fracastorius._--See his _De
Sympathia_, lib. i., cap. 5 (Giunta edition, 1574, p. 60).
[159] PAGE 68, LINE 5. Page 68, line 6. _Thaletis Milesij._--See the note
to p. 11, line 26.
[160] PAGE 68, LINE 30. Page 68, line 35. _Ità coitio magnetica actus est
magnetis, & ferri, non actio vnius._--See the introductory remarks to these
notes. There is a passage in Scaliger's _De Subtilitate ad Cardanum_
(Exercitat. CII., cap. 5, p. 156 _op. citat._) which may be compared with
Gilbert's for its use of Greek terms: "Nã cùm uita dicatur actus animæ,
acceptus est abs te actus pro actione. Sed actus ille est [Greek:
entelecheia], nõ autem [Greek: ergon]. At Magnetis attractio est [Greek:
ergon], non aut[~e] [Greek: entelecheia]." To which Gilbert retorts: "non
actio unius, utriusque [Greek: entelecheia]; non [Greek: ergon], [Greek:
sunentelecheia] et conactus potius quam sympathia." He returns on p. 70 to
the attack on Scaliger's metaphysical notions. There is a parallel passage
in the _Epitome Naturalis Scientiæ_ of Daniel Sennert (Oxoniæ, 1664), in
the chapter _De Motu_.
[161] PAGE 71, LINE 4. Page 71, line 8. _vt in 8. physicorum Themistius
existimat._--See _Omnia Themistii Opera_ (Aldine edition, 1533, p. 63),
Book 8 of his Paraphrase on Aristotle's _Physica_.
[162] PAGE 71, LINE 9. Page 71, line 14. _Quod verò Fracastorius._--_Op.
citat._, lib. i., cap. 7, p. 62 _verso_.
[163] PAGE 73, LINE 2. Page 73, line 2. _si A borealis._--The editions of
1628 and 1633 omit the twelve words next following.
[164] PAGE 73, LINE 9. Page 73, line 11. _ex minera._--_Minera_ is not a
recognized word, even in late Latin. It occurs again, p. 97, line 12.
[165] PAGE 77, LINE 2. Page 77, line 2. _multo magis._--This is an _à
fortiori_ argument. It is interesting to find Gilbert comparing the
velocity of propagation of magnetic forces in space with the velocity of
light. The parallel is completed in line 13 by the consideration that as
the rays of light require to fall upon an object in order that they may
become visible, so the magnetic forces require a magnetic object in order
to render their presence sensible.
[166] PAGE 78, LINE 14. Page 78, line 16. _Orbem terrarum
distinguunt._--The editions of 1628 and 1633 here add a figure of a globe
marked with meridians and parallels of latitude, but with an erroneous
versorium pointing to the south. These editions also both read
_existentiam_ for the word _existentium_ in line 20.
[167] PAGE 83, LINE 5. Page 83, line 5. _magnes longior maiora pondera
ferri attollit._--Gilbert discovered the advantage, for an equal mass of
loadstone, of an elongated shape. It is now well known that the specific
amount of magnetism retained by elongated forms exceeds that in a short
piece of the same material subjected to equal magnetizing forces.
[168] PAGE 83, LINE 24. Page 83, line 28. _Non obstant crassa
tabulata._--Gilbert has several times referred (_e.g._, on p. 77) to the
way in which magnetic forces penetrate solid bodies. The experimental
investigation in this chapter {47} is the more interesting because it shows
that Gilbert clearly perceived the shielding action of iron to be due to
iron conducting aside or diverting the magnetic forces.
[169] PAGE 85, LINE 26. Page 85, line 31. _non conveniant._--The editions
of 1628 and 1633 both read _et conveniant_.
[170] PAGE 86, LINE 3. Page 86, line 3. _illud quod exhalat._--Literally,
_that which exhales_, in the sense of that which escapes: but in modern
English the verb exhale in the active voice is now not used of the
substance that escapes, but is used of the thing which emits it. It must
therefore be rendered _that which is exhaled_ (_i.e._, breathed out).
[171] PAGE 86, LINE 13. Page 86, line 15. _Ita tota interposita moles
terrestris._--Gilbert's notion that the gravitational force of the moon in
producing the tides acts _through_ the substance of the earth may seem
curiously expressed. But the underlying contention is essentially true
to-day. The force of gravity is not cut off or screened off by the
interposition of other masses. A recent investigation by Professor
Poynting, F.R.S., has shown that so far as all evidence goes all bodies,
even the densest, are transparent with respect to gravitational forces.
[172] PAGE 86, LINE 18. Page 86, line 20. _Sed de æstus ratione
aliàs._--There is no further discussion of the tides in _De Magnete_. But a
short account is to be found in Gilbert's posthumous work _De Mundo nostro
Sublunari Philosophia nova_ (Amsterdam, Elzevir, 1651), in Lib. v., the
part which in the manuscript was left in English, and was turned into Latin
by his brother. It comprises about fifteen quarto pages, from Cap. X. to
Cap. XIX. inclusive, beginning with a characteristic diatribe against
Taisnier, Levinus Lemnius, and Scaliger. But in assigning causes he himself
goes wide of the mark. Proceeding by a process of elimination he first
shows that the moon's light cannot be the cause that impels the tides.
"Luna," he says, "non radio, non lumine, maria impellit. quomodo igitur?
Sane corporum conspiratione, acque (ut similitudine rem exponam) Magnetica
attractione." This cryptic utterance he proceeds to explain by a diagram,
and adds: "Quare Luna non tam attrahit mare, quàm humorem & spiritum
subterraneum; nec plus resistit interposita terra, quàm mensa, aut quicquam
aliud densum, aut crassum, magnetis viribus."
[173] PAGE 87, LINE 7. Page 87, line 9. _armatura._--Here this means the
cap or snout of iron with which the loadstone was armed. This is apparently
the first use of the term in this sense.
In the _Dialogues of Galileo_ (p. 369 of Salusbury's _Mathematical
Collections_, Dialogue iii.), Sagredus and Salviatus discuss the arming of
the loadstone, and the increased lifting power conferred by adding an iron
cap. Salviatus mentions a loadstone in the Florentine Academy which,
unarmed, weighed six ounces, lifting only two ounces, but which when armed
took up 160 ounces. Whereupon Galileo makes Salviatus say: "I extreamly
praise, admire, and envy this Authour, for that a conceit so stupendious
should come into his minde. ... I think him [_i.e._, Gilbert] moreover
worthy of extraordinary applause for the many new and true Observations
that he made, to the disgrace of so many fabulous Authours, that write not
only what they do not know, but whatever they hear spoken by the foolish
vulgar, never seeking to assure themselves of the same by experience,
perhaps, because they are unwilling to diminish the bulk of their Books."
[174] PAGE 87, LINE 12. Page 87, line 15. The reference to _lib._ 3 is {48}
a misprint for _lib._ 2. It is corrected in the edition of 1633, but not in
that of 1628.
[175] PAGE 87, LINE 17. Page 87, line 21. _conactu._--The editions of 1628
and 1633 read _conatu_.
[176] PAGE 88, LINE 2. Page 88, line 3. _Coitio verò non fortior._--This
heading to chap. xix., taken with the seven lines that follow, and the
contrast drawn between _unitio_ and _coitio_, throw much light on the
fundamental sense attached by Gilbert to the term _coitio_. It is here
clearly used in the sense of _mutual tendency toward union_. Note also the
contrasted use in chap. xx. of the verbs _cohære_ and _adhære_. Adhærence
connotes a one-sided force (an impossibility in physics), cohærence a
mutual force.
[177] PAGE 90, LINE 9. Page 90, line 9. _nempè vt alter polus maius pondus
arripiat._--This acute observation is even now not as well known as it
ought to be. Only so recently as 1861 Siemens patented the device of
fastening a mass of iron to one end of an electromagnet in order to
increase the power of the other end. The fact, so far as it relates to
permanent magnets was known to Servington Savery. See _Philos.
Transactions_, 1729, p. 295.
[178] PAGE 92, LINE 3. Page 92, line 4. _Suspendit in aëre ferrum Baptista
Porta._--Porta's experiment is thus described (_Natural Magick_, London,
1658, p. 204): "_Petrus Pellegrinus_ saith, he shewed in another work how
that might be done: but that work is not to be found. Why I think it
extream hard, I shall say afterwards. But I say it may be done, because I
have now done it, to hold it fast by an invisible band, to hang in the air;
onely so, that it be bound with a small thread beneath, that it may not
rise higher: and then striving to catch hold of the stone above, it will
hang in the air, and tremble and wag itself."
[179] PAGE 97, LINE 29. Page 97, line 33. _Sed quæri potest ..._--The
question here raised by Gilbert is whether the lifting-power of magnets of
equal quality is proportional to their weight. If a stone weighing a drachm
will lift a drachm, would a stone that weighs an ounce lift an ounce?
Gilbert erroneously answers that this is so, and that the lifting-power of
a loadstone, whether armed or unarmed, is proportional to its mass.
The true law of the tractive force or lifting-power of magnets was first
given in 1729 by James Hamilton (afterwards Earl of Abercorn) in a work
entitled _Calculations and Tables Relating to the Attractive Virtue of
Loadstones ... Printed_ [at London?] _in the Year_ 1729. (See also a paper
in the _Philos. Transactions_, 1729-30, vol. xxxvi., p. 245). This work
begins thus:
"The Principle upon which these Tables are formed, is this: That if Two
_Loadstones_ are perfectly Homogeneous, that is, if their Matter be of the
same Specifick Gravity, and of the same Virtue in all Parts of one Stone,
as in the other; and that Like Parts of their Surfaces are Cap'd or Arm'd
with Iron; then the Weights they sustain will be as the Squares of the Cube
Roots of the Weights of the _Loadstones_; that is, as their Surfaces."
Upon lifting-power see also D. Bernoulli, _Acta Helvetica_, iii., p. 223,
1758; P. W. Haecker, _Zur Theorie des Magnetismus_, Nürnberg, 1856; Van der
Willigen, _Arch. du Musée Teyler_, vol. iv., Haarlem, 1878 ; S. P.
Thompson, _Philos. Magazine_, July, 1888.
In the book of James Hamilton, p. 5, he mentions a small terrella weighing
139 English grains, which would sustain no less than 23,760 grains, and was
valued at £21 13s. 10¾d.
{49} In the _Musæum Septalianum_ of Terzagus (Dertonæ, 1664, p. 42) is
mentioned a loadstone weighing twelve ounces which would lift sixty pounds
of iron.
Sir Isaac Newton had a loadstone weighing 3 grains, which he wore in a
ring. It would lift 746 grains.
Thomson's _British Annual_, 1837, p. 354, gives the following reference:
"In the _Records of General Science_, vol. iii., p. 272, there is an
interesting description of a very powerful magnet which was sent from
Virginia in 1776 by the celebrated Dr. Franklin to Professor Anderson, of
Glasgow. It is now in the possession of Mr. Crichton. It weighs 2½ grains,
and is capable of supporting a load of 783 grains, which is equivalent to
313 times its own weight."
[180] PAGE 99, LINE 10. Page 99, line 11. _Manifestum est._--In this, as in
many other passages, Gilbert uses this expression in the sense that _it is
demonstrable_ rather than meaning that _it is obvious_: for the fact here
described is one that is not at all self-evident, but one which would
become plain when the experiment had been tried. For other instances of
this use of _manifestum_ see pages 144, line 20; 158, line 19; 162, line
10.
[181] PAGE 100, LINE 20. Page 100, line 24. _si per impedim[=e]ta ...
pervenire possunt._--All editions agree in this reading, but the sense
undoubtedly requires _non possint_. Compare p. 91, line 21.
[182] PAGE 102, LINE 4. Page 102, line 4. _capite_ 4.--This is a misprint
for _capite_ 40, and is retained in the later editions. In the quotation
from Baptista Porta, where the English version of 1658 is adhæred to, the
words "& deturbat eam" have been omitted by the translator.
[183] PAGE 107, LINE 16. Page 107, line 18. _Cardanus scribit._--The
alleged perpetual motion machine is mentioned in _De rerum varietate_,
_lib._ 9, cap. xlviii. (Basil., 1581, p. 641). See also the Note to p. 223.
For Peregrinus and for Taisnier, see the note to p. 5, lines 8 and 12.
[184] PAGE 107, LINE 19. Page 107, line 21. _Antonij de Fantis._--His work
is: _Tabula generalis scotice subtilitatis octo Sectionibus vniuersam
Doctoris Subtilis Periti[=a] c[=o]plect[=e]s: ab excellentissimo doctore
Antonio de F[=a]tis taruisino edita ..._ Lugd., 1530.
[185] PAGE 108, LINE 26. Page 108, line 31. _Cusani in staticis._--See the
note to p. 64, line 16.
[186] PAGE 108, LINE 33. Page 108, line 41. _Languidi ... tardiùs
acquiescunt._--The editions of 1628 and 1633 omit these seven words.
[187] PAGE 109, LINE 11. Page 109, line 13. _halinitro._--Either native
carbonate of soda or native carbonate of potash might be meant, but not
saltpetre. Scaliger, in his _De Subtilitate ad Cardanum_ (Lutet., 1557, p.
164), _Exercitatio_ CIII., 15, under the title, _Nitrum non est Salpetræ_,
says: "More tuo te, tuaque confundis. Salpetræ inter salis fossilis ponis
hîc. Mox Halinitrum inter salis, & nitri naturam, speciem obtinere."
"_Sal nitrum_ is salt which is boiled out of the earth, especially fat
earth, as in stables, or any place of excrements." (_A Chymicall Dictionary
explaining Hard Places and Words met withall in the Writings of Paracelsus
..._, Lond., 1650.)
[188] PAGE 109, LINE 20. Page 109, line 23. _arte ioculatoriâ._--Edition
1628, _joculatoriâ_; edition 1633, _jaculatoriâ_.
[189] PAGE 110, LINE 11. Page 110, line 12. _qualis fuit Antonij
denarius._--The Elizabethan version of Pliny (book xxxiii., ch. ix., p.
479) runs thus: {50} "To come now unto those that counterfeit money.
_Antonius_ whiles hee was one of the three usurping Triumvirs, mixed yron
with the Romane silver denier. He tempered it also with the brasen coine,
and so sent abroad false and counterfeit money."
Georgius Agricola (_De Natura Fossilium_, p. 646) says:
"Sed ea fraus capitalis est, non aliter ac eorum qui adulterinas monetas
cudunt, argento miscentes multam plumbi candidi portionem, aut etiam ferri,
qualis fuit Antonii denarius, ut Plinius memoriæ tradidit. Nunc dicam de
candido plumbo, nam majoris pretii est quàm aes. In quod plumbum album,
inquit Plinius, addita aeris tertia portione candidi adulteratur stannum."
[190] PAGE 111, LINE 3. Page 111, line 3. _Meminerunt Chatochitis lapis
Plinius, atque Iulius Solinus._--The passage in Pliny (English version of
1601, book xxxvii., ch. x., p. 625) runs:
"Catochitis is a stone proper unto the Island Corsica: in bignesse it
exceedeth ordinarie pretious stones: a wonderfull stone, if all be true
that is reported thereof, and namely, That if a man lay his hand thereon,
it will hold it fast in manner of a glewie gum."
[191] PAGE 111, LINE 7. Page 111, line 7. _Sagda vel Sagdo._--Albertus
Magnus in _De Mineralibus_ (Venet., 1542, p. 202) says:
"Sarda quem alij dicunt Sardo lapis est qui se habet ad tabulas ligni sicut
magnes ad ferr[=u], et ideo adhæret ita fortiter tabulis nauium quòd euelli
n[=o] possit, nisi abscindatur cum ipso ea pars tabulæ cui inhæserit, est
aut[=e] in colore purissimus nitens."
And Pliny (_op. citat._, p. 629):
"Sagda is a stone, which the Chaldeans find sticking to ships, and they say
it is greene as Porrets or Leekes."
[192] PAGE 111, LINE 8. Page 111, line 8. _Euace._--Evax, king of the
Arabs, is said to have written to Nero a treatise on the names, colours,
and properties of stones. See the note on Marbodæus, p. 7, line 20.
[193] PAGE 113, LINE 14. Page 113, line 19. _repulsus sit._ The words read
thus in all editions, but the sense requires _repulsa sint._
[194] PAGE 113, LINE 23. Page 113, line 29. _Electrica omnia alliciunt
cuncta, nihil omninò fugant vnquam, aut propellunt._ This denial of
electrical repulsion probably arose from the smallness of the pieces of
electric material with which Gilbert worked. He could hardly have failed to
notice it had he used large pieces of amber or of sealing-wax. Electrical
repulsion was first observed by Nicolas Cabeus, _Philosophia Magnetica_,
Ferrara, 1629; but first systematically announced by Otto von Guericke in
his treatise _Experimenta Nova (ut vocantur) Magdeburgica, de Vacuo Spatio_
(Amstel., 1672).
[195] PAGE 113, LINE 29. Page 113, line 37. _cùm de calore quid sit
disputabimus._--The discussion of the nature of heat is to be found in
Gilbert's _De Mundo nostro Sublunari_ (Amstel., 1651), lib. i., cap. xxvi.,
pp. 77-88.
[196] PAGE 115, LINE 23. Page 115, line 23. _trium vel quatuor
digitorum._--Here as in all other places in Gilbert, _digitus_ means a
finger's breadth, so that three or four digits means a length of two or
three inches, or from six to eight centimetres.
[197] PAGE 117, LINE 26. Page 117, line 25. _ille Thebit Bencoræ
trepidationis motus._
"Trepidation in the ancient Astronomy denotes a motion which in the
Ptolemaic system was attributed to the firmament, in order to account for
{51} several changes and motions observed in the axis of the world, and for
which they could not account on any other principle." (Barlow's
_Mathematical Dictionary_.)
[198] PAGE 118, LINE 10. Page 118, line 8. _cuspis is aut lilium._--Gilbert
uses _cuspis_ or _lilium_ always of the North-pointing end of the needle.
Sir Thomas Browne speaks of "the lilly or northern point"; but he differs
from Gilbert in saying "the _cuspis_ or Southern point" (_Pseudodoxia
Epidemica_, 1650, p. 46). Only in one place (p. 101, line 5) does Gilbert
speak of _cuspis meridionalis_. Everywhere else the south-pointing end is
called the _crux_.
[199] PAGE 118, LINE 15. Page 118, line 13. _nam æquè potens est._--Later
observation showed this view to be incorrect. The horizontal component of
the earth's magnetic field is not equally strong all over the globe, and
the sluggishness of the needle's return to its position of rest is not due
to the supporting pin becoming blunt with wear. The value of the horizontal
component is zero at the north magnetic pole, and increases toward the
magnetic equator. It is greatest near Singapore and in Borneo, being there
more than twice as great as it is at London. (See Captain Creak in _Report
of Voyage of H.M.S. Challenger, Physics and Chemistry_, vol. ii., part vi.,
1889.)
[200] PAGE 119, LINE 5. Page 119, line 2. _lapis._--Both Stettin editions
read _lapidis._
[201] PAGE 119, LINES 9-11. Page 119, lines 7-9. The gist of the whole book
is summarized in these lines. They furnish a cardinal example of that
inductive reasoning which was practist by Gilbert, and of which Bacon
subsequently posed as the apostle. Compare pages 41 and 211.
[202] PAGE 120, LINE 8. Page 120, line 5. _dicturi sumus_.--Change of
verticity is treated of in book iii., chap. x., pp. 137 to 140.
[203] PAGE 125, LINE 24. Page 125, line 29. _appositam._--All editions give
this word, though the sense requires _appositum._
[204] PAGE 128, LINE 9. Page 128, line 11. _non nimis longum._--The
editions of 1628 and 1633 read (wrongly) _minus_ instead of _nimis_.
[205] PAGE 130, LINE 12. Page 130, line 14. The word _hunc_ in the folio of
1600 is corrected in ink to _tunc_, and the Stettin editions both read
_tunc_.
[206] PAGE 132, LINE 9. Page 132, line 10. _minimus & nullius
ponderis._--The editions of 1628 and 1633 both wrongly read _est_ for _&_.
[207] PAGE 132, LINE 28. Page 133, line 1. _nutat._--The editions of 1628
and 1633 both wrongly read _mutat_.
[208] PAGE 134, LINE 22. Page 134, line 25. _in rectâ sphærâ._--The meaning
of the terms a _right_ or _direct sphere_, an _oblique sphere_ and a
_parallel sphere_ are explained by Moxon on pages 29 to 31 of his book _A
Tutor to Astronomy and Geography_ (Lond., 1686):
"A _Direct Sphere_ hath both the _Poles_ of the _World_ in the Horizon ...
It is called a _Direct Sphere_, because all the _Celestial_ Bodies, as
_Sun_, _Moon_, and _Stars_, &c. By the _Diurnal_ Motion of the _Primum
Mobile_, ascend directly Above, and descend directly Below the _Horizon_.
They that Inhabit under the _Equator_ have the _Sphere_ thus posited."
"An _Oblique Sphere_ hath the _Axis_ of the _World_ neither _Direct_ nor
_Parallel_ to the _Horizon_, but lies aslope from it."
"A _Parallel Sphere_ hath one _Pole_ of the _World_ in the _Zenith_, the
other in the _Nadir_, and the _Equinoctial_ Line in the _Horizon_."
[209] PAGE 136, LINE 1. Page 136, line 1. _præsenti._--The editions of 1628
and 1633 read _sequenti_, to suit the altered position of the figure.
[210] PAGE 137, LINE 24. {52} Page 137, line 28. _atque ille statim._--The
Stettin editions both wrongly read illi.
[211] PAGE 139. There is a curious history to this picture of the
blacksmith in his smithy striking the iron while it lies north and south,
and so magnetizing it under the influence of the earth's magnetism.
Woodcuts containing human figures are comparatively rare in English art of
the sixteenth century; a notable exception being Foxe's _Acts and
Monuments_ with its many crude cuts of martyrdoms. The artist who prepared
this cut of the smith took the design from an illustrated book of Fables by
one Cornelius Kiliani or Cornelius van Kiel entitled _Viridarium Moralis
Philosophiæ, per Fabulas Animalibus brutis attributas traditæ, etc._
(Coloniæ, 1594). This rare work, of which there is no copy in the British
Museum, is illustrated by some 120 fine copper-plate etchings printed in
the text. On p. 133 of this work is an etching to illustrate the fable
_Ferrarii fabri et canis_, representing the smith smiting iron on the
anvil, whilst his lazy dog sleeps beneath the bellows. The cut on p. 139 of
Gilbert gives, as will be seen by a comparison of the pictures just the
same general detail of forge and tools; but the position of the smith is
reversed right for left, the dog is omitted, and the words _Septrenio_ and
_Auster_ have been added.
[Illustration]
In the Stettin edition of 1628 the picture has again been turned into a
copper-plate etching separately printed, is reversed back again left for
right, while a compass-card is introduced in the corner to mark the
north-south direction.
In the Stettin edition of 1633 the artist has gone back to Kiliani's
original {53} plate, and has re-etched the design very carefully, but
reversing it all right for left. As in the London version of 1600, the dog
is omitted, and the words _Septentrio_ and _Auster_ are added. Some of the
original details--for example, the vice and one pair of pincers--are left
out, but other details, for instance, the cracks in the blocks that support
the water-tub, and the dress of the blacksmith, are rendered with slavish
fidelity.
It is perhaps needless to remark that the twelve copper-plate etchings in
the edition of 1628, and the twelve completely different ones in that of
1633, replace certain of the woodcuts of the folio of 1600. For example,
take the woodcut on p. 203 of the 1600 edition, which represents a simple
dipping-needle made by thrusting a versorium through a bit of cork and
floating it, immersed, in a goblet of water. In the 1633 edition this
appears, slightly reduced, as a small inserted copper-plate, with nothing
added; but in the 1628 edition it is elaborated into a full-page plate (No.
xi.) representing the interior, with shelves of books, of a library on the
floor of which stands the goblet--apparently three feet high--with a globe
and an armillary sphere; while beside the goblet, with his back to the
spectator, is seated an aged man, reading, in a carved armchair. This
figure and the view of the library are unquestionably
copied--reversed--from a well-known plate in the work _Le Diverse &
Artificiose Machine_ of Agostino Ramelli (Paris, 1558).
In the Emblems of Jacob Cats (_Alle de Wercken_, Amsterdam, 1665, p. 65) is
given an engraved plate of a smith's forge, which is also copied--omitting
the smith--from Kiliani's _Viridarium_.
[212] PAGE 140, LINE 2.. Page 140, line 2. _præcedenti._--This is so
spelled in all editions, though the sense requires _præcedente_.
[213] PAGE 141, LINE 21. Page 141, line 24. _quod in epistolâ quâdam
Italicâ scribitur._--The tale told by Filippo Costa of Mantua about the
magnetism acquired by the iron rod on the tower of the church of St.
Augustine in Rimini is historical. The church was dedicated to St. John,
but in the custody of the Augustinian monks. The following is the account
of it given by Aldrovandi, _Musæum Metallicum_ (1648, p. 134), on which
page also two figures of it are given:
"Aliquando etiam ferrum suam mutat substantiam, dum in magnetem
conuertitur, & hoc experientia constat, nam Arimini supra turrim templi S.
Ioannis erat Crux a baculo ferreo ponderis centum librarum sustentata, quod
tractu temporis adeò naturam Magnetis est adeptum, vt, illivs instar,
ferrum traheret: hinc magna admiratione multi tenentur, qua ratione ferrum,
quod est metallum in Magnetem, qui est lapis transmutari possit;
Animaduertendum est id à maxima familiaritate & sympathia ferri, & magnetis
dimanare cum Aristoteles in habentibus symbolum facilem transitum semper
admiserit. Hoc in loco damus imaginem frusti ferri in Magnetem transmutati,
quod clarissimo viro Vlyssi Aldrouando Iulius Caesar Moderatus diligens
rerum naturalium inquisitor communicauit; erat hoc frustum ferri colore
nigro, & ferrugineo, crusta exteriori quodammodo albicante." And further on
p. 557.
"Preterea id manifestissimum est; quoniam Arimini, in templo Sancti
Ioannis, fuit Crux ferrea, quæ tractu temporis in magnetem conuersa est, &
ab vno latere ferrum trahebat, & ab altero respuebat." See also Sir T.
Browne's _Pseudodoxia Epidemica_ (edition of 1650, p. 48), and Boyle's
tract, _Experiments and Notes about the Mechanical Production of Magnetism_
(London, 1676, p. 12).
{54} Another case is mentioned in Dr. Martin Lister's _A Journey to Paris_
(Lond., 1699, p. 83). "He [Mr. Butterfield] shewed us a Loadstone sawed off
that piece of the Iron Bar which held the Stones together at the very top
of the Steeple of _Chartres_. This was a thick Crust of Rust, part of which
was turned into a strong Loadstone, and had all the properties of a Stone
dug out of the Mine. _Mons. de la Hire_ has Printed a Memoir of it; also
Mons. _de Vallemont_ a Treatise. The very outward Rust had no Magnetic
Virtue, but the inward had a strong one, as to take up a third part more
than its weight unshod." Gassendi and Grimaldi have given other cases.
Other examples of iron acquiring strong permanent magnetism from the earth
are not wanting. The following is from Sir W. Snow Harris's _Rudimentary
Magnetism_ (London, 1872, p. 10).
"In the _Memoirs of the Academy of Sciences_ for 1731, we find an account
of a large bell at Marseilles having an axis of iron: this axis rested on
stone blocks, and threw off from time to time great quantities of rust,
which, mixing with the particles of stone and the oil used to facilitate
the motion, became conglomerated into a hardened mass: this mass had all
the properties of the native magnet. The bell is supposed to have been in
the same position for 400 years."
[214] PAGE 142, LINE 13. Page 142, line 15. _tunc planetæ & corpora
coelestia._--Gilbert's extraordinary detachment from all metaphysical and
ultra-physical explanations of physical facts, and his continual appeal to
the test of experimental evidence, enabled him to lift the science of the
magnet out of the slough of the dark ages. This passage, however, reveals
that he still gave credence to the _nativities_ of judicial Astrology, and
to the supposed influence of the planets on human destiny.
[215] PAGE 144, LINE 14. Page 144, line 14. _ijdem._--The editions of 1628
and 1633 erroneously read _iisdem_.
[216] PAGE 147, LINE 27. Page 147, line 29. _ex optimo aciario._--Gilbert
recommended that the compass-needle should be of the best steel. Though the
distinction between iron and steel was not at this time well established,
there is no reason to doubt that by _aciarium_ was meant edge-steel as used
for blades. Barlowe, in his _Magneticall Advertisements_ (Lond., 1616), p.
66, gives minute instructions for the fashioning of the compass-needle. He
gives the preference to a pointed oval form, and describes how the steel
must be hardened by heating to whiteness and quenching in water, so that it
is "brickle in a manner as glass it selfe," and then be tempered by
reheating it over a bar of red hot iron until it is let down to a blue
tint. Savery (_Philos. Trans._, 1729) appears to have been the first to
make a systematic examination of the magnetic differences between hard
steel and soft iron.
Instructions for touching the needle are given in the _Arte de Nauegar_ of
Pedro de Medina (Valladolid, 1545, lib. vi., cap. 1).
[217] PAGE 149, LINE 8. Page 149, line 9. _per multa sæcula._--Compare
Porta's assertion (p. 208, English edition) "iron once rubbed will hold the
vertue a hundred years." Clearly not a matter within the actual experience
of either Porta or Gilbert.
[218] PAGE 153, LINE 2. Page 153, line 2. _Cardani ab ortu stellæ in cauda
vrsæ._--What Cardan said (_De Subtilitate_, _Edit. citat._, p. 187) was:
"ortum stellæ in cauda ursæ minoris, quæ quinque partibus orientalior est
polo mundi, respicit."
[219] PAGE 153, LINE 21. Page 153, line 26. _sequitur quod versus terram
magnam, siue continentem ... à vero polo inclinatio magnetica
fiat._--Gilbert {55} goes on to point out how, at that date, all the way up
the west European coast from Morocco to Norway, the compass is deflected
eastward, or toward the elevated land. He argued that this was a universal
law.
In _Purchas his Pilgrimes_ (Lond., 1625), in the Narrative, in vol. iii.,
of Bylot and Baffin's Voyage of 1616, there is mentioned an island between
Whale-Sound and Smith's Sound, where there had been observed a larger
variation than in any other part of the world. Purchas, in a marginal note,
comments on this as follows: "Variation of the Compass 56° to the West,
which may make questionable D. Gilbert's rule, tom. 1., l. 2, c. 1, that
where more Earth is more attraction of the Compass happeneth by variation
towards it. Now the known Continents of Asia, &c., must be unspeakably more
than here there can be, & yet here is more variation then about Jepan,
Brasil, or Peru, &c."
Gilbert's view was in truth founded on an incomplete set of facts. At that
time, as he tells us, the variation of the compass at London was 11-1/3
degrees eastward. But he did not know of the secular change which would in
about fifty-seven years reduce that variation to zero. Still less did he
imagine that there would then begin a westward variation which in the year
1816 should reach 24° 30', and which should then steadily diminish so that
in the year 1900 it should stand at 16° 16' westward. For an early
discussion of the changes of the variation see vol. i. of the
_Philosophical Transactions_ (Abridged), p. 188. Still earlier is the
classical volume of Henry Gellibrand, _A Discovrse Mathematical on the
Variation of the Magneticall Needle_ (Lond., 1635). Gilbert heads chapter
iii. of book iiii. (p. 159) with the assertion _Variatio uniuscuiusque loci
constans est_, declaring that to change it would require the upheaval of a
continent. Gellibrand combats this on p. 7 of the work mentioned. He says:
"Thus hitherto (according to the Tenents of all our _Magneticall_
Philosophers) we have supposed the variations of all particular places
to continue one and the same. So that when a Seaman shall happly
returne to a place where formerly he found the same variation, he may
hence conclude he is in the same former _Longitude_. For it is the
Assertion of _Mr. Dr. Gilberts_. _Variatio vnicuiusq; Loci constans
est_, that is to say, the same place doth alwayes retaine the same
variation. Neither hath this Assertion (for ought I ever heard) been
questioned by any man. But most diligent magneticall observations have
plainely offred violence to the same, and proved the contrary, namely
that the variation is accompanied with a variation."
In 1637 Henry Bond wrote in the _Sea-Mans Kalendar_ that in the year 1657
the variation would be zero at London. Compare Bond's _Longitude Found_
(Lond., 1676, p. 3).
As to inconstancy of the variation in one place see further Fournier's
_Hydrographie_ (Paris, 1667, liv. xi., ch. 12, p. 413), and Kircher,
_Magnes_ (Colon. Agripp., 1643, p. 418).
[220] PAGE 157, LINE 4. Page 157, line 5. _perfecto._--Though this word is
thus in all editions, it ought to stand _perfectâ_, as in line 10 below.
[221] PAGE 157, LINE 11. Page 157, line 13. _varietas_, for _variatio_.
[222] PAGE 160, LINE 20. Page 160, line 23. _in Borrholybicum._--This name
for the North-west, or North-North-West, is rarely used. It is found on the
chart or windrose of the names of the winds on pp. 151 and 152 of the
_Mécometrie de l'Eyman_ of G. Nautonier (1602). Here the name
_Borrolybicus_ is given as a synonym for _Nortouest Galerne_, or [Greek:
Olumpias], while the two winds on the points next on the western and
northern sides respectively are called _Upocorus_ and _Upocircius_.
{56} In Swan's _Specvlvm Mundi_ (Camb., 1643, p. 174) is this explanation:
"Borrholybicus is the North-west wind."
In Kircher's _Magnes_ (Colon. Agripp., 1643, p. 434) is a table of the
names of the thirty-two winds in six languages, where _Borrolybicus_ is
given as the equivalent of _Maestro_ or _North-West_.
[223] PAGE 161, LINE 2. Page 161, line 2. _Insula in Oceano variationem non
mutat._--The conclusions derived from the magnetic explorations of the
Challenger expedition, 1873-1876, are briefly these: That in islands north
of the magnetic equator there is a tendency to produce a local
perturbation, attracting the north-seeking end of the needle downwards, and
horizontally towards the higher parts of the land; while south of the
magnetic equator, the opposite effects are observed. (See _Challenger
Reports, Physics and Chemistry_, vol. ii., part vi., _Report on the
Magnetical Results_ by Staff-Commander Creak, F.R.S.)
[224] PAGE 162, LINE 2. Page 162, line 3. _quarè & respectiuum punctum ...
excogitauit._--The passage referred to is in _The newe Attractiue_ of
Robert Norman (Lond., 1581), chap. vi.
"Your reason towards the earth carrieth some probabilitie, but I prove that
there be no _Attractive_, or drawing propertie in neyther of these two
partes, then is the _Attractive_ poynt lost, and falsly called the poynt
_Attractive_, as shall be proved. But because there is a certayne point
that the Needle alwayes respecteth or sheweth, being voide and without any
_Attractive_ propertie: in my judgment this poynt ought rather to bee
called the point Respective ... This Poynt _Respective_, is a certayne
poynt, which the touched Needle doth alwayes _Respect_ or shew ..."
[225] PAGE 165, LINE 2. Page 165, line 2. _De pyxidis nauticæ vsitatæ
compositione._--Gilbert's description of the usual construction of the
mariner's compass should be compared with those given by Levinus Lemnius in
_The Secret Miracles of Nature_ (London, 1658); by Lipenius in _Navigatio
Salomonis Ophiritica_ (Witteb., 1660, p. 333); and with that given in
Barlowe's _Navigators Supply_ (London, 1597). See also Robert Dudley's
_Dell' Arcano del Mare_ (Firenze, 1646).
[226] PAGE 165 deals with the construction; the process of magnetizing by
the loadstone had already been discussed in pp. 147 to 149. It is
interesting to see that already the magnetized part attached below the
compass-card was being specialized in form, being made either of two pieces
bent to meet at their ends, or of a single oval piece with elongated ends.
The marking of the compass-card is particularly described. It was divided
into thirty-two points or "winds," precisely as the earlier "wind-rose" of
the geographers, distinguisht by certain marks, and by a lily--or
fleur-de-lys--indicating the North. Stevin in the _Havenfinding Art_
(London, 1599), from which work the passage on p. 167 is quoted, speaking
on p. 20 of "the Instrument which we call the Sea-directorie, some the
nautical box, ... or the sea compasse," mentions the "Floure de luce"
marking the North.
The legend which assigns the invention of the compass to one Goia or Gioja
of Amalfi in 1302 has been already discussed in the Note to page 4. Gilbert
generously says that in spite of the adverse evidence he does not wish to
deprive the Amalfians of the honour of the construction adopted in the
compasses used in the Mediterranean. But Baptista Porta the Neapolitan, who
wrote forty years before Gilbert, discredited the legend. "_Flavius_ saith,
an Italian found it out first, whose name was _Amalphus_, born in our {57}
Campania. But he knew not the Mariners Card, but stuck the needle in a
reed, or a piece of wood, cross over; and he put the needles into a vessel
full of water that they might flote freely." (Porta's _Natural Magick_,
English translation, London, 1658, p. 206.) See also Lipenius (_op. citat._
p. 390).
The pivotting of the needle is expressly described in the famous _Epistle_
on the Magnet of Peter Peregrinus, which was written in 1269. Gasser's
edition, _Epistola Petri Peregrini ... de magnete_, was printed in Augsburg
in 1558. In Part II., cap. 2, of this letter, a form of instrument is
described for directing one's course to towns and islands, and any places
in fact on land or sea. This instrument consists of a vessel like a turned
box (or _pyxis_) of wood, brass, or any solid material, not deep, but
sufficiently wide, provided with a cover of glass or crystal. In its middle
is arranged a slender axis of brass or silver, pivotted at its two ends
into the top and the bottom of the box. This axis is pierced orthogonally
with two holes, through one of which is passed the steel needle, while
through the other is fixed square across the needle another stylus of
silver or brass. The glass cover was to be marked with two cross lines
north-south and east-west; and each quadrant was to be divided into ninety
degrees. This the earliest described pivotted compass was therefore of the
cross-needle type, a form claimed as a new invention by Barlowe in 1597.
The first suggestion of suspending a magnetic needle by a thread appears to
be in the _Speculum Lapidum_ of Camillus Leonardus (Venet., 1502, fig. k
ij, lines 25-31): "Nã tacto ferro ex una [=p]te magnetis ex opposita eius
[=p]te appropinquato fugat: ut ex[=p]i[~e]tia docet de acu appenso filo."
The earliest known examples of the "wind-rose" are those in certain
parchment charts preserved in the Biblioteca Marciana in Venice. These go
back to 1426 or 1436, the best being ascribed to Andrea Bianco. They have
the North indicated by a fleur-de-lys, a trident, a simple triangle, or a
letter T; while the East is distinguisht by a cross. The West is marked
with a P. (see Fincati, _op. citat._). The eight marks in order, clock
wise, run thus,
[Lily] (or T). G. [Cross] (or L) S. O. A (or L). P. M.
The letters correspond to the Italian names of the principal winds:
Tramontano North.
Greco North-East.
Levante East.
Sirocco South-East.
Ostro South.
Africo or Libeccio South-West.
Ponente West.
Maestro North-West.
Wind-roses marked with the names of the minor winds are found in
Nautonier's _Mécometrie de l'Eyman_ (Vennes, 1602-1604, pp. 151-152), and
Kircher's _Magnes Siue de Arte Magnetica_ (Colon. Agripp., 1643, p. 432).
The description above given of the early Venetian wind-roses _exactly_
describes the compass-card as depicted by Pedro de Medina in his _Arte de
Nauegar_ (Valladolid, 1545, folio lxxx.), in the sixth book entitled "las
aguias de navegar"; while in the _Breve compendio de la sphera_ of Martin
Cortes (Sevilla, 1551, cap. iii., _de la piedrayman_) a similar wind-rose,
without the letters, is found.
{58} In the _De Ventis et navigatione_ of Michaele Angelo Blondo (Venet.,
1546, p. 15) is given a wind-rose, described as "Pixis uel Buxolus
instrumentum et dux nauigantium," having twenty-six points inscribed with
the names of the winds, there being six between north and east, and six
between south and west, and only five in each of the other quadrants. In
the middle is a smaller wind-rose exactly like the early Italian ones just
mentioned.
In the _Della Guerra di Rhodi_ of Jacobo Fontano (Venet., 1545, pages
71-74) is a chapter _Dei Venti, e della Bvssola di nauicare di Giovanni
Quintino_, giving a wind-rose, and a table of the names of the winds, the
north being indicated by a pointer, at the cusp of which are seven stars,
and the west by an image of the sun. The other cardinal points are marked
with letters.
Barlowe, in _The Navigators Supply_ (Lond., 1597), speaks thus:
"The merueilous and diuine Instrument, called the _Sayling Compasse_
(being one of the greatest wonders that this World hath) is a Circle
diuided commonly into 32. partes, tearmed by our Seamen Windes,
_Rumbes_, or Points of Compasse."
It is a disputed point with whom the method of naming the winds originated.
Some ascribe it to Charlemagne. Michiel Coignet (_Instruction novvelle ...
touchant l'art de naviguer_, Anvers, 1581, p. 7) ascribes it to Andronicus
Cyrrhestes. See Varro, _De Re Rustica_, iii., 5, 17, and Vitruvius, i., 6,
4.
Gilbert's complaint of the evil practice of setting the needles obliquely
beneath the card, with the intention of allowing for the variation, is an
echo of a similar complaint in Norman's _Newe Attractiue_. In chapter x. of
this work Norman thus enumerates the different kinds of compasses:
"Of these common Sayling Compasses, I find heere (in _Europa_) five
sundry sortes or sets. The first is of _Levant_, made in _Scicile_,
_Genoüa_, and _Venice_: And these are all (for the most parte) made
Meridionally, with the Wyers directlye sette under the South, and North
of the Compasse: And therefore, duely shewing the poynt _Respective_,
in all places, as the bare Needle. And by this Compasse are the Plats
made, for the most part of all the _Levants_ Seas.
"Secondly, there are made in _Danske_, in the Sound of _Denmarke_, and
in _Flanders_, that have the Wyers set at 3 quarters of a point to the
Eastwards of the North of the compasse, and also some at a whole point:
and by these Compasses they make both the Plats and Rutters for the
Sound.
"Thirdly, there hath beene made in this Countrey particulary, for Saint
_Nicholas_ and _Ruscia_, Compasses set at 3 seconds of a point, and the
first Plats of that Discoverie were made by this Compasse.
"Fourthly the Compasse made at _Sevill_, _Lisbone_, _Rochell_,
_Bourdeaux_, _Roan_, and heere in _England_, are moste commonly set at
halfe a point: And by this Compasse are the Plats of the East and West
_Indies_ made for their Pylotes, and also for our Coastes neere hereby,
as _France_, _Spayne_, _Portugall_, and _England_: and therefore best
of these Nations to bee used, because it is the most common sorte that
is generally used in these Coastes."
Bessard (_op. citat._, pages 22 and 48) gives cuts of compasses showing the
needle displaced one rumbe to the East.
Gallucci, in his _Ratio fabricandi horaria mobilia et permanentia cum
magnetica acu_ (Venet., 1596), describes the needle as inclined 10 degrees
from the south toward the south-west.
The frontispiece of the work of Pedro Nuñez, _Instrumenta Artis Navigandi_,
Basil., 1592, depicts a compass with the lily set one point to the east.
Reibelt, _De Physicis et Pragmaticis Magnetis Mysteriis_ (Herbipolis,
1731), depicts the compass with the needle set about 12 degrees to the East
of North. See also Fournier, _Hydrographie_ (Paris 1667); De Lanis,
_Magisterium Natvræ et Artis_ (Brixiæ, 1684); Milliet Deschales, _Cursus
seu Mundus {59} Mathematicus_ (Lugd., 1674). Both the latter works give
pictures of the compass-cards as used in South Europe, and in North Europe,
and of the various known shapes of needles.
[227] PAGE 168, LINE 29. Page 168, line 33. _Directio igitur inualidior est
propè polos._ Here as in many passages _direction_ means _the force which
directs_. A similar usage prevails with the nouns _variation_ and
_declination_, meaning frequently the force causing variation or
declination respectively.
PAGE 172, LINE 13. _perquirere._ The edition of 1633 reads _perquirero_, in
error.
[228] PAGE 172, LINE 29. Page 172, line 33. _Ad pyxidis nauticæ veræ &
meridionalis formam ... fiat instrumentum._--An excellent form of portable
meridian compass, provided with sights for taking astronomical
observations, is described by Barlowe (_The Navigators Supply_, London,
1597), and is depicted in an etched engraving. An identical engraving is
repeated in Dudley's _Arcano del Mare_ (Firenze, 1646). Gilbert's new
instrument was considerably larger.
[229] PAGE 174, LINE 19. Page 174, line 21. _addendo vel detrahendo
prostaphæresin._--"Prosthaphæresis, conflata dictione, ex additione et
subtractione speciebus logistices, nomen habet ab officio, quia vt in
semicirculo altero ad æquabilem motum adijcitur, ita in altero subtrahitur,
vt adparens motus ex æquabili taxetur: atque hinc fit, quòd quæ
Prosthaphæresis dicitur Ptolemæo, ea vulgò æquatio vocetur." (Stadius,
_Tabulæ Bergenses_, Colon. Agripp., 1560, p. 37.)
[230] PAGE 174, LINE 28. Page 174, line 31. _Stellæ Lucidæ._--According to
Dr. Marke Ridley (_Magneticall Animadversions_, London, 1617, p. 9), this
chapter xii. of book iv., with the Table of Stars, was written by Edward
Wright, the author of the Prefatory Epistle of _De Magnete_. Wright was
Lecturer on Navigation to the East India Company, and author of sundry
treatises on Navigation.
[231] PAGE 187, LINE 14. Page 187, line 16. _hic qui versus boream
constitit ... meridionalis est, non borealis, quem antè nos omnes
existimabant esse borealem._--Earlier on, on pages 15 and 125, Gilbert had
mentioned this point. His insistence caused Barlowe (_Magneticall
Aduertisements_, 1616, p. 4) to speak of the south-pointing end of the
needle as the "true North," and thereby drew on himself the animadversions
of Marke Ridley.
[232] PAGE 188, LINE 15. Page 188, line 16. _in rectâ sphærâ._--See note to
p. 134.
[233] PAGE 190, LINE 14. Page 190, line 19. _declinans in
Borealibus._--Dipping as it does in northern regions; that is, with the
north-seeking or true-south pole downward.
[234] PAGE 195, LINE 20. Page 195, line 24. _multa maiora pondera._--Many
greater weights. All editions read _multa_, but the sense requires _multo_:
"much greater weights."
[235] PAGE 196, LINE 10. Page 196, line 12. _constans est._--This must not
be read "is constant," for it is constant only in any given latitude.
[236] PAGE 196, LINE 15. Page 196, line 18. _De proportione declinationis
pro latitudinis ratione._--Gilbert here announces, and proceeds in the next
seven pages to develop, the proposition that to each latitude there
corresponds a constant dip to a particular number of degrees. If this were
accurately so, then a traveller by merely measuring the dip would be able
to ascertain, by calculation, by reference to tables, or by aid of some
geometrical appliance, {60} the latitude of the place. In this hope Gilbert
fought to perfect the dipping-needle; and he also worked out, on pages 199
and 200, an empirical theory, and a diagram. This theory was still further
developed by him, and given to Thomas Blundevile (see the Note to p. 240).
Briggs of Gresham College, on Gilbert's suggestion, calculated a table of
Dip and Latitude on this theory. It was found, however, that the observed
facts deviated more or less widely from the theory. Kircher (_Magnes_,
1643, p. 368) gives a comparative table of the computed and observed
values. Further discovery showed the method to be impracticable, and
Gilbert's hope remained unfulfilled.
[237] PAGE 197, LINE 18. Page 197, line 21. _progressionis centri._--Note
Gilbert's precision of phrase.
[238] PAGE 200, LINE 12. Page 200, line 11. _subintellig[=u]tur._--This is
printed _subintelligitur_, and is altered in ink in all copies of the folio
edition. The editions of 1628 and 1633 read _subintelliguntur_. Similarly
in line 14 the word _ducit_ has had a small _r_ added in ink, making it
read _ducitur_, as also the other editions.
[239] PAGE 203. This figure of the experiment with the simple dipping
needle suspended in water in a goblet is due to Robert Norman. In his _Newe
Attractiue_ (London, 1581, chap. vi.) he thus describes it:
"Then you shall take a deepe Glasse, Bowle, Cuppe, or other vessell,
and fill it with fayre water, setting it in some place where it may
rest quiet, and out of the winde. This done, cut the Corke
circumspectly, by little and little, untill the wyre with the Corke be
so fitted, that it may remain under the superficies of the water two or
three inches, both ends of the wyer lying levell with the superficies
of the water, without ascending or descending, like to the beame of a
payre of ballance beeing equalie poysed at both ends.
"Then take out of the same the wyer without mooving the Corke, and
touch it with the _Stone_, the one end with the South of the _Stone_,
and the other end with the North, and then set it againe in the water,
and you shall see it presentlie turne it selfe upon his owne Center,
shewing the aforesay'd _Declining_ propertie, without descending to the
bottome, as by reason it should, if there were any _Attraction_
downewards, the lower part of the water being neerer that point, then
the superficies thereof."
[240] PAGE 212, LINE 7. Page 212, line 8. _ex altera parte._--The sense
seems to require _et altera parte_, but all editions read _ex_.
[241] PAGE 213, LINE 1. Page 213, line 2. The passage here quoted from
Dominicus Maria Ferrariensis, otherwise known as the astronomer Novara,
does not occur in any known writing of that famous man. It is, however,
quoted as being by Novara in at least three other writings of the same
epoch. See the _Tabulæ secvndorum mobilium coelestium_ of Maginus (Venet.,
1585, p. 29, line 19 to p. 30, line 11); the _Eratosthenes Batavvs_ of
Willebrord Snell (Lugd. Batav., 1617, pp. 40-42); and the _Almagesti novi
(Pars Posterior)_ of Riccioli (Bonon., 1651, p. 348). The original document
appears to have perisht. See a notice by M. Curtze in Boncompagni's
_Bullettino di Bibliografia_, T. iv., April, 1871.
[242] PAGE 214, LINE 26. Page 214, line 31. _Philolaus Pythagoricus._
"Philolaüs a le premier dit que la terre se meut en cercle; d'autres
disent que c'est Nicétas de Syracuse."
"Les uns prétendent que le terre est immobile; mais Philolaüs le
pythagoricien dit qu'elle se meut circulairement autour du feu
(central) et suivant un cercle oblique, comme le soleil et la
lune."--(Chaignet, _Pythagore et la Philosophie pythagoricienne_,
Paris, 1873.)
It appears that the first of these _dicta_ is taken from Diogenes Laërt.,
viii. 85; and the second from Plutarch, _Placit. Philos._, III. 7. The
latter {61} passage may be compared with Aristotle, _De Coelo_, II. 13,
who, referring to the followers of Pythagoras, says: "They say that the
middle is fire, that the earth is a star, and that it is moved circularly
about this centre; and that by this movement it produces day and night."
[243] PAGE 214, LINE 34. Page 214, line 42. _Copernicus._--His work is _De
revolutionibus orbium coelestium, libri vi._ (Basil., 1566).
[244] PAGE 215, LINE 27. Page 215, line 24. _quæ ... in cælo varijs
distantijs collocata sunt._--This remark appears to be Gilbert's one
contribution to the science of Astronomy; the stars having previously been
regarded as fixed in the eighth sphere all at the same distance from the
central earth, around which it revolved.
[245] PAGE 220, LINE 6. Page 220, line 6. _quem nycthemeron vocamus._--The
1628 and 1633 editions read _nyctemoron_.
[246] PAGE 221, LINE 10. Page 221, line 11. _poli verè oppositi sint._--For
_verè_, the 1628 and 1633 editions read _rectæ_. All editions read _sint_,
though _sunt_ seems to make better sense.
[247] PAGE 223, LINE 7. Page 223, line 8. _ad telluris conformitatem._--The
word _conformitas_ is unknown in classical Latin.
[248] PAGE 223, LINE 16. Page 223, line 17. _Omitto quod Petrus Peregrinus
constanter affirmat, terrellam super polos suos in meridiano suspensam,
moveri circulariter integrâ revolutione 24 horis: Quod tamen nobis adhuc
videre non contingit; de quo motu etiam dubitamus._
This statement that a spherical loadstone pivotted freely with its axis
parallel to the earth's axis will of itself revolve on its axis once a day
under the control of the heavens, thus superseding clocks, is to be found
at the end of chap. x. of Peregrinus's _Epistola De Magnete_ (Augsb.,
1537).
Gilbert, who doubted this experiment because of the stone's own weight is
taken to task by Galileo, in the third of his Dialogues, for his qualified
admission.
"I will speak of one particular, to which I could have wished that
_Gilbert_ had not lent an ear; I mean that of admitting, that in case a
little Sphere of Loadstone might be exactly librated, it would revolve in
it self; because there is no reason why it should do so" (p. 376 of
Salusbury's _Mathematical Collections_, London, 1661). The Jesuit Fathers
who followed Gilbert, but rejected his Copernican ideas, pounced upon this
pseudo-experiment, as though by disproving it they had upset the Copernican
theory.
[249] PAGE 227, LINE 6. Page 227, line 7. This line is left out in the 1628
edition. In the 1633 edition it was also left out by the printer, and
subsequently printed in in the margin, being page 219 of that edition.
[250] PAGE 234, LINE 35. Page 234, line 40. _vt poli telluris respectus à
polis._--If it may be permitted to read _respectu_ for _respectus_ the
sense is improved, and the passage may then be translated thus: "that just
as it was needful ... that the poles of the Earth as to direction should be
23 degrees and more from the poles of the Ecliptick; so now, &c."
[251] PAGE 237, LINE 19. Page 237, line 22. _vt motus quidem obscuri
saluarentur._--It has been conjectured that _quidem_ is here a misprint for
_quidam_, but the adverb _quidem_ adds a satirical flavour to his argument
against the folly of those who held the doctrine of the moving spheres. The
verb _salvare_ does not occur in classical Latin.
[252] PAGE 240, LINE 13. Page 240, line 17. _à Copernico (Astronomiæ
instauratore)._--Gilbert was the first in England to uphold the doctrines
of {62} Copernicus as to the motion of the earth on its axis and its
revolution around the sun. He considered that his magnetic observations
brought new support to that theory, and his views are quoted with
approbation by Kepler, _Epitome Astronomiæ Copernicanæ_ ... Authore Ioanne
Keplero ... (Francofurti, 1635); and by Galileo, _Dialogus de Systemate
Mundi_ (Augustæ Treboc., 1635), an English translation of which appeared in
Salusbury's _Mathematical Collections and Translations_ (London, 1661, pp.
364 to 377).
For this the book _De Magnete_ was considered by many as heretical. Many of
the copies existing in Italy are found to be either mutilated or else
branded with a cross. For example, the copy in the library of the Collegio
Romano in Rome has book VI. torn out. Galileo states that the Book of
Gilbert would possibly never have come into his hands "if a Peripatetick
Philosopher, of great fame, as I believe to free his Library from its
contagion, had not given it me." In England Barlowe, in his _Magneticall
Aduertisements_ (1616), expressly repudiated Gilbert's Copernican notions,
while praising his discoveries in magnetism. Marke Ridley, while upholding
Gilbert's views, in his _Magneticall Animadversions_ (1617) did not
consider him "skilfull in Copernicus." The Jesuit writers, Cabeus, Kircher,
Fonseca, Grandamicus, Schott, Leotaudus, Millietus, and De Lanis, one and
all, who followed Gilbert in their magnetic writings, repudiated the idea
that the magnetism of the globe gave support to the heretical modern
Astronomy.
The works referred to are:
Cabeus, _Philosophia Magnetica, in qua Magnetis natura penitus explicatur
... auctore Nicolao Cabeo Ferrarensi Soc. Jesv._ (Ferrariæ, 1629).
Kircher, _Magnes, Siue de Arte Magnetica, Libri tres, Authore Athanasio
Kirchero ... e Soc. Iesv._ (Romæ, 1641).
Grandamicus, _Nova Demonstratio immobilitatis terræ petita ex virtute
magnetica_ (Flexiæ, 1645). This work is most beautifully illustrated with
copper-plate etchings of cupids making experiments with terrellas.
Schott, Gaspar, _Thaumaturgus Physicus_ (Herbipolis, 1659).
Leotaudus, _R. P. Vincentinii Leotavdi Delphinatis, Societ. Iesv.,
Magnetologia; in qva exponitvr Nova de Magneticis Philosophia_, (Lvgdvni,
1668).
Millietus (Milliet Deschales), _Cursus seu Mundus Mathematicus_ (Lugd.,
1674), _Tomus Primus, Tractatus de Magnete_.
De Lanis, _Magisterium Natvræ et Artis. Opus Physico-Mathematicvm P.
Francisci Tertii de Lanis, Soc. Jesv._ (Brixiæ, 1684).
[253] PAGE 240, LINE 24. Page 240, line 31. _hic finem & periodum
imponimus._
On February 13 [1601] Gilbert wrote to Barlowe (see _Magneticall
Aduertisements_, p. 88):
"I purpose to adioyne an appendix of six or eight sheets of paper to my
booke after a while, I am in hand with it of some new inventions, and I
would haue some of your experiments, in your name and inuention put into
it, if you please, that you may be knowen for an augmenter of that arte."
This he never did. Perhaps his appointment (in February, 1601) as chief
physician in personal attendance on the Queen interfered with the project;
or his death, of the plague, in 1603, intervened before his intention had
been carried into effect. But it is probable that the substance of the
proposed additions is to be found in the chapter, publisht in Gilbert's
lifetime, in Blundevile's _Theoriques of the seuen Planets_ (London, 1602),
thus described in the title-page of the work: "There is also hereto added,
{63} The making, description, and vse, of two most ingenious and necessarie
Instruments for Sea-men, to find out thereby the latitude of any Place vpon
the Sea or Land, in the darkest night that is, without the helpe of Sunne,
Moone, or Starre. First inuented by M. Doctor Gilbert, a most excellent
Philosopher, and one of the ordinarie Physicians to her Maiestie: and now
here plainely set downe in our mother tongue by Master Blundeuile."
Of these two instruments the first consists of a mechanical device, with
movable quadrants, to be cut out in cardboard, to be used in connection
with the diagram of spiral lines which Gilbert had given as a folding plate
between pages 200 and 201 of _De Magnete_. The intention was that the
Sea-man having found by experiment with a dipping-needle the amount of the
dip at any place, should by applying this diagram and its moving quadrants,
ascertain the latitude, according to the theory expounded in book V., chap.
VII.
The second instrument is a simplified portable dipping-needle, having the
degrees engraved on the inner face of a cylindrical brass ring.
Blundevile adds a Table, calculated by Briggs, and "annexed to the former
Treatise by _Edward Wright_, at the motion of the right Worshipful M.
Doctor _Gilbert_." This gives the values of the dip for different
latitudes, as calculated from Gilbert's empirical theory.
The other work, _De Mundo nostro Sublunari Philosophia Nova_, which Gilbert
left in manuscript at his death, does not contain any additional matter on
the magnetical investigations. Though it contains several direct references
to the _de Magnete_, and particularly to Book VI. on the rotation of the
earth, it is doubtful whether it was written after or before the
publication of _de Magnete_. On pages 137 to 144 of the posthumous edition
(Amsterdam, 1651) Gilbert refers to Peregrinus's alleged perpetually
revolving sphere, and denies its possibility. The greater part of the work
is an anti-Aristotelian discussion on Air, Meteorology, Astronomy, the
Winds, Tides, and Springs.
[Illustration]
* * * * *
{65} INDEX TO AUTHORITIES
Abano, Pietro di, 6.
Acosta, Josephus, 16.
Addison, Joseph, 35.
Aepinus, 44.
Aetius Amidenus, 6.
Affaytatus, 16, 39.
Agricola, Georgius, 25, 31, 36, 50.
Agrippa, H. Cornelius, 7.
Albategnius, 29.
Albertus Magnus, 6, 17, 38, 39, 40, 50.
Aldrovandi, Ulisse, 13, 36, 53.
Alexander Aphrodiseus, 3, 21.
Amatus Lusitanus, 6, 31.
Apponensis, Petrus, 6. _See_ Abano.
Aquinas, St. Thomas, 8, 45.
Ardoynis, Santes de, 6.
Aristotle, 4, 19, 25, 61.
Arnaldus de Villa nova, 6.
Augustani, 29.
Augustine, St., 4, 21, 43.
Aurifaber, 36.
Averroes, 29.
Avicenna, 6, 29, 30, 34.
Azuni, 8.
Bacon, Lord, 17, 42.
Barlow, Peter, 51.
Barlowe, William, 1, 2, 5, 9, 20, 28, 54, 56, 57, 58, 59, 62.
Beckmann, Johann, 19, 21, 32.
Bencora, or Ben Korrah (Thebitius), 30.
Benjamin, Park, 9, 11, 17.
Bernoulli, D., 48.
Bertelli, Timoteo, 11.
Bessard, Toussaincte de, 11, 58.
Bianco, Andrea, 57.
Blackmore, R. D., 24.
Blondo, Michaele Angelo, 1, 58.
Blondus, Flavius, 9.
Blundevile, Thomas, 8, 14, 60, 62, 63.
Bond, Henry, 55.
Borough, William, 2, 19.
Boyle, Robert, 43, 53.
Brasavolus, Antonius Musa, 6, 37.
Briggs, Henry, 60, 62.
Brough, R. B., 15.
Browne, Sir Thomas, 3, 37, 42, 51, 53.
Brunfels, Otho, 17, 30.
Buffum, W. A., 36.
Burton, Sir Richard F., 5.
Buttmann, 20, 32.
Buxtorf, 21.
Cabeus, Nicolas, 2, 42, 50, 62.
Cabot, Sebastian, 10, 16.
Caesar (or Cesare, Giulio), 53.
Calaber, Hannibal Rosetius, 6.
Calcagninus, Cælius, 8, 9.
Camden, William, 25.
Camera, Matteo, 8.
Cardan, Hieronymo, 23, 24, 26, 31, 36, 37, 41, 43, 49, 54.
Casaubon, 17.
Cats, Jacob, 53.
Cavallo, Tiberius, 44.
Chaignet, 60.
Charlemagne, 58.
Charles II., 23.
Charleton, Dr. W., 19.
Chladni, 26.
Coignet, Michiel, 58.
Collenuccio, Pandolfo, 9.
Conimbricenses, 11.
Cordus, Valerius, 20.
Cortes, Martin, 11, 24, 57.
Costa, Filippo, 16, 53.
Costa, Joseph. _See_ Acosta.
Costaeus, Joannes, of Lodi, 16, 45.
Creak, Captain, 51, 56.
Creech, T., 3.
Crescentius, 8.
Crollius, O., 29.
Curtius, 32.
Curtius, N., 29.
Curtze, M., 60.
Cusan (Cardinal de Cusa), 7, 45, 49.
Cyrrhestes, Andronicus, 58.
Davies, T. S., 20.
De la Hire, 54.
De Lanis, 58, 62.
Delaunay, 32.
Diogenes Laertius, 60.
Dioscorides, 30, 34, 35, 37, 38, 43.
Dominicus Maria Ferrariensis (Novara), 60.
Drake, Sir Francis, 19.
Dudley, Sir Robert, 19, 56, 59.
Du Puys (Puteanus), 38, 45.
{66}
Encelius, _or_ Entzelt, 7, 24, 26.
Erastus, Thomas, 7.
Euripides, 4.
Evax, 18, 50.
Evelyn, John, 23.
Fallopius, Gabriellus, 7, 29.
Fantis, Antonius de, 49.
Ficino, Marsiglio, 18.
Fincati, Admiral, 8.
Fletcher, L., 26.
Fonseca, 62.
Fontano, Jacopo, 58.
Forcellini, 2.
Fournier, G., 10, 20, 22, 55, 58.
Foxe, 52.
Fracastorio, Hieronymo, 12, 19, 29, 51.
Galen, 29, 30, 31, 35.
Galileo, 47, 62.
Gallucci, 58.
Gartias ab Horto, 13, 27, 39.
Gassendi, 54.
Gasser, Achilles P., 17, 57.
Geber, 29.
Gellibrand, Henry, 55.
Gemma, Cornelius, 45.
Gessner, 32.
Gilbert, Adrian, 20.
Gilbert, William, _de Mundo nostro Sublunari_, 47, 50, 63.
Gioia, _or_ Goia, 8, 56.
Glanvill, Joseph, 27.
Goebel, 36.
Goethe, 23.
Gonzalus Oviedus, 10.
Goppert, 35.
Goropius, Henricus Becanus, 10.
Gralath, D., 36.
Grandamicus, 62.
Grew, N., 23.
Grimaldi, 54.
Grotius, Hugo, 17.
Guericke, Otto von, 41, 50.
Haecker, P. W., 48.
Hakewill, G., 10.
Hakluyt, 13, 20.
Hali Abbas, 6, 17, 29.
Hamilton, James (Earl of Abercorn), 48.
Hariot, Thomas, 19.
Harris, Sir W. Snow, 21, 54.
Hartmann, P. J., 36.
Hellmann, G., 11.
Hermann, D., 36.
Hermolaus Barbarus, 7.
Hill, "Sir" John, 24, 38, 40.
Hood, T., 3.
Hues, Robert, 19.
Humboldt, 26, 31, 36, 41.
Hyginus, 36.
Isidore, St., 20, 21, 39.
Kendall, Abraham, 19.
Kepler, 62.
Kiel, Cornelius van (_or_ Kiliani), 52.
King, Edward, 26.
Kircher, Athanasius, 2, 21, 45, 55, 56, 57, 62.
Klaproth, 7, 8, 10, 20, 21, 22.
Kudrun, 15.
Langius, Joannes, 7.
Lanis, F. de, 58, 62.
Leonardus, Camillus, 7, 57.
Leotaudus, 62.
Levinus Lemnius, 38, 39, 41, 56.
Libri, 11.
Linna, Nicolas de, 14.
Lipenius, 13, 56.
Lister, Martin, 53.
Livio Sanuto, 10, 16.
Livy, 26.
Lonicer, Joannes, 30, 35, 38.
Löwy, 21.
Lucretius, 3, 44.
Maginus, 60.
Magnus, Sir Philip, 10.
Manardus, Joannes, 29.
Marbodeus, 6, 18, 21, 40, 41, 50.
Marcellus Empiricus, 6, 7.
Marco Polo, 10.
Martial, 36, 37.
Martin, Th. Henri, 20, 21, 32, 33.
Maskelyne, N. Story, 26.
Matthæus Silvaticus, 7.
Matthiolus, P., 5, 30, 35.
Maurolycus, Franciscus, 11.
Medina, Pedro de, 54, 57.
Mercator, 11, 14.
Merula, Gaudentius, 18, 19.
Merula, P., 15.
Miers, H. A., 40.
Migne, 19.
Milliet Deschales, 58, 62.
Monardus, Nicolas, 29.
Montanus, Joannes Baptista, 6.
Morris, William, 15.
Moxon, Joseph, 51.
Muellenhoff, K., 36.
Nautonier, G., 55, 57.
Neckham, Alexander of, 10.
Newton, Sir Isaac, 41.
Nicander, 38.
Nicolaus Myrepsius (_or_ Præpositas), 28, 35.
{67}
Nonius Petrus (_or_ Nuñez), 58.
Nordenskjold, 13.
Norman, Robert, 1, 11, 14, 28, 56, 58, 60.
Novara, Dominicus Maria, 60.
Offusius, Joannes Franciscus, 31.
Olaus Magnus, 12, 17.
Oribasius, 6.
Orpheus, 22, 44.
Ovid, 36.
Oviedo, Luis de, 28.
Oviedus, Gonzalus, 10.
Paley, F. A., 32.
Palm, G. A., 20.
Paracelsus (Bombast von Hohenheim), 7, 29.
Paulus Aeginæ, 30.
Paulus Jovius, 9.
Paulus Venetus (Fra Paolo Sarpi), 17.
Pepys, Samuel, 23.
Peregrinus, Petrus, 1, 11, 23, 48, 57, 61.
Pettus, Sir John, 23, 41.
Philolaus, 60.
Photius, 21.
Pictorio, G., 18.
Plancius, 14.
Plat, Sir Hugh, 5, 40, 43.
Plato, 4, 44.
Plautus, 2.
Pliny (Caius Plinius Secundus), 5, 20, 21, 22, 24, 25, 26, 27, 35, 36,
37, 38, 39, 41, 49, 50.
Plot, Rob., 42.
Plutarch, 26, 28, 41, 60.
Polo, Marco, 10.
Porta, Joannes Baptista (Giambattista della Porta), 4, 9, 16, 23, 46, 48,
54, 56, 57.
Poynting, J. H., 47.
Præpositas (_or_ Nicolas Myrepsius), 28, 35.
Ptolemy, 12, 28.
Purchas, 55.
Puteanus, Gulielmus, 38, 45.
Quintino, Giovanni, 58.
Ramelli, Agostino, 53.
Rammelsberg, 26.
Reibelt, 58.
Rhazes, 28, 29, 30.
Riccioli, 60.
Ridley, Marke, 3, 31, 59, 62.
Robertson, Rev. Alexander, 17.
Rücker, Arthur W., 15.
Ruellius, Joannes, 18, 30, 34, 37.
Rueus, Franciscus, 17.
Ruysch, Johan, 13.
Salusbury, T., 61, 62.
Santes de Ardoynis, 6.
Sanuto, Livio, 10, 16.
Sarpi, Fra Paolo, 16, 17.
Savery, Servington, 48, 54.
Scaliger, J. C., 26, 33, 34, 45, 46, 49.
Scheins, M., 32.
Schindler, A. Houtum, 33.
Schott, G., 62.
Schweigger, J. C., 32.
Sendel, Nathaniel, 36, 37.
Sennert, Daniel, 46.
Serapio, 6, 17, 30.
Severt, Jacques, 11.
Shakespeare, William, 22.
Siemens, 48.
Signorelli, 8.
Silvaticus, Matthæus, 7.
Smith, Dr. William, 26.
Snell, Willebrord, 60.
Solinus, Julius, 4, 37, 40.
Stadius, 59.
Stephanus, 32.
Stevinus, Simon, 56.
Strabo, 26.
Swan, John, 56.
Swinden, J. H. van, 44.
Taisnier, Joannes, 11, 47.
Terzagus, 36, 49.
Thalèn, 15.
Thales, 46.
Thebit Ben Korrah, 30, 50.
Themistius, 46.
Theophrastus, 32, 36, 38.
Thompson, Silvanus P., 48.
Thomson, R. D., 49.
Thorpe, T. E., 15.
Vallemont, Abbé de, 54.
Van Swinden, 44.
Varro, 58.
Venanson, Flaminius, 8.
Venner, Dr. T., 40.
Vergil, 2, 24.
Virgil, Polydore, 9.
Vitruvius, 58.
Waring, E. J., 29.
Watson, William, 38.
Wigand, Johann, 36.
Wilde, Henry, 15.
Willigen, van der, 48.
Wren, Sir Christopher, 23.
Wright, Edward, 19, 59, 62.
[Illustration]
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