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Title: Essays on the use and limit of the imagination in science
Author: John Tyndall
Release date: October 29, 2024 [eBook #74654]
Language: English
Original publication: London: Longmans, Green & Co
Credits: Tim Lindell, Laura Natal and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK ESSAYS ON THE USE AND LIMIT OF THE IMAGINATION IN SCIENCE ***
ESSAYS
ON THE
USE AND LIMIT
OF THE
IMAGINATION IN SCIENCE.
BY
JOHN TYNDALL, LL.D., F.R.S.
LONDON:
LONGMANS, GREEN, AND CO.
1870.
EXPLANATORY NOTE.
[Illustration]
To a Second Edition of a Discourse on the Scientific Use of the
Imagination, delivered before the British Association at Liverpool
on September 16, 1870, are here added an Address on the Limit of the
Imagination in Science, delivered before the Mathematical and Physical
Section of the Association at Norwich on August 19, 1868, and a short
Essay, entitled ‘Earlier Thoughts.’
The Address and the Essay were meant to be brief, but definite
statements of the relation of Life and Consciousness to Matter and
Force.
As in the case of the recent Discourse, opinion was divided with
regard to the objects and merits of the Norwich Address. On the one
hand, two eminent clergymen, one of the Church of England, the other a
Dissenter, proposed and seconded respectively a vote of thanks, which
was liberally carried by the section; on the other hand, I was publicly
warned that, as a consequence of my impiety, the bolts of heaven were
in a state of potential suspension above my head, ready to descend if
further drawn upon.
My main object, both at Norwich and at Liverpool, was, firstly, to
dissipate the repugnance, and indeed terror, which in many minds are
associated with the thought that science has abolished the mystery of
man’s relation to the universe; and, secondly, to remove the hindrance
which popular notions regarding the origin of life oppose to legitimate
scientific speculation.
ATHENÆUM CLUB: _November_ 1870.
CONTENTS.
[Illustration]
PAGE
PROS AND CONS TOUCHING THE FIRST EDITION 1
SCIENTIFIC USE OF THE IMAGINATION 13
SCIENTIFIC LIMIT OF THE IMAGINATION 52
EARLIER THOUGHTS 66
PROS AND CONS
TOUCHING THE FIRST EDITION.
[Illustration]
_From the_ TIMES, _Sept._ 19, 1870.
THE GLORY of a Natural Philosopher appears to depend less on the
power of his imagination to explore minute recesses or immeasurable
space than on the skill and patience with which, by observation
and experiment, he assures us of the certainty of these invisible
operations. Newton’s glory is founded, not on the sudden imagination
by which he leapt ‘from a falling apple to a falling moon,’ but on
that astonishing tenacity of investigation by which he reduced his
guesses to moral certainties, and enabled us to witness a practical
verification of his laws in every almanack we use. When the movements
of the heavenly bodies have been discovered by this laborious process,
the imagination is excellently employed in picturing to the mind’s eye
what transcends the physical vision; and, perhaps, the labour of the
investigation itself would be unendurable unless the attention could be
relieved by the constant pictorial aid afforded by the imagination....
In a word, it seems to us worth consideration whether that use of the
imagination in Natural Philosophy of which the Professor speaks needed
any encouragement at the present day. The discoveries of science
have been so astonishing, the new worlds they have opened to us are
so vast, that there is, perhaps, more danger of our imagination being
exercised too freely than of its not being exercised sufficiently upon
them. No one will dispute the claim of the Professor to be one of the
privileged spirits of whom he speaks, if there are any such, and he
proceeds accordingly to exercise his imagination, not upon the little
germ-cells, but upon that vast primordial nebulous envelope out of
which, according to the opinion to which some philosophers incline,
all the infinite complexity of the existing world has been developed.
We are not privileged spirits, and we own ourselves not altogether
able to follow him when he leads us into the imaginary realms of the
original chaos. He confesses that Mr. Darwin ‘has drawn heavily upon
time and adventurously upon matter.’ We ask ourselves again whether
we are listening to one experimental philosopher describing the
achievements of another experimental philosopher. We had been under
the impression that Natural Philosophers drew no bills. We do not
presume to say one word about the Evolution Hypothesis. We neither
affirm nor deny that Professor Tyndall existed in a nebulous state an
infinite number of centuries ago. We only venture to suggest that when
the British Association amuse the public with these speculations they
are illustrating, not the scientific use of the imagination, but the
imaginative use of science.
_From the_ SATURDAY REVIEW, _Sept._ 24, 1870.
Here, too, we question whether Sir William Thomson will be content
with this definition of the process by which he has been guided to
his most recent advance in molecular physics. In the splendid series
of inductions verified step after step by rigorous experiment
and observation, and kept in exactest continuity by the chain of
mathematical evolution, is imagination the faculty to which are
to be given the chief honours of this conquest of a new realm of
physics? This would surely be to force upon us a new and arbitrary
classification or analysis of the powers of the intellect. If we follow
Professor Tyndall himself through the masterly train of reasoning
whereby he leads us to the laws of reflection and transmission of light
as the cause of the azure of the firmament, is what we admire the
leap of imagination, or the firmly balanced and duly graduated tread
of a mind trained in the discipline of logic, and careful to plant
every step on the assured ground of fact or experience? It is simply
a misnomer to apply the name of imagination to the process or the
faculty to which this onward march into the realm of unexplored nature
is really due. As well describe as a triumph of the imagination the
connected and organized plan of the great strategist which has drawn
round Paris a living cordon of 300,000 men.
_From a Lecture addressed to Teachers at the South Kensington Museum,
April 30, 1861, by_ J. TYNDALL.
Here, then, is an exhibition of power which we can call forth or cause
to disappear at pleasure. We magnetize our strip of steel by drawing
it along the pole of a magnet; we can demagnetize it, or reverse its
magnetism, by properly drawing it along the same pole in the opposite
direction. What, then, is the real nature of this wondrous change? What
is it that takes place among the atoms of the steel when the substance
is magnetized? The question leads us beyond the region of sense, and
into that of imagination. This faculty, indeed, is the divining rod
of the man of science. Not, however, an imagination which catches its
creations from the air, but one informed and inspired by facts, capable
of seizing firmly on a physical image as a principle, of discerning its
consequences, and of devising means whereby these forecasts of thought
may be brought to an experimental test. If such a principle be adequate
to account for all the phenomena, if from an assumed cause the observed
facts necessarily follow, we call the assumption a theory, and once
possessing it, we can not only revive at pleasure facts already known,
but we can predict others which we have never seen. Thus, then, in the
prosecution of physical science, our powers of observation, memory,
imagination, and inference, are all drawn upon. We observe facts and
store them up; imagination broods upon these memories, and by the
aid of reason tries to discern their interdependence. The theoretic
principle flashes, or slowly dawns upon the mind, and then the
deductive faculty interposes to carry out the principle to its logical
consequences. A perfect theory gives dominion over natural facts;
and even an assumption which can only partially stand the test of a
comparison with facts, may be of eminent use in enabling us to connect
and classify groups of phenomena.
_From the_ GUARDIAN, _Sept._ 21, 1870.
He held some pieces of paper in his hand, but he rarely referred to
them. Thoroughly possessed by his subject, his thoughts seemed to
flow forth with perfect ease, fresh minted as they were in the most
appropriate and perspicuous words. He led his hearers gently and almost
unconsciously through the most perplexed mazes and subtlest passages
of thought, keeping their ears enchained and their fancy charmed by
the endless succession of apt metaphor; and yet, whenever he felt or
fancied that their overstrained attention began to flag, he was able to
turn aside into light and pleasant banter, and after this interlude of
welcome refreshment, to resume again with renewed power the unbroken
thread of his serious discourse. It was the manifest work of a master
in his art, handling with ease and grace the weighty tools which long
use had made familiar to his hand.
_From the_ ENGLISH CHURCHMAN, _Sept._ 29, 1870.
What astonishes us beyond measure is, that a man of Professor Tyndall’s
real ability and earnestness should sneer at the second verse of the
Bible, and speak of it as a legend! Why, surely, he has here the very
thing which he is searching--the true origin of life. When chaos
ruled over the world, and the earth was void of life; it was the
Divine Spirit that breathed over the lifeless mass, and light and life
sprang into existence. Without stopping to point out the evidence of
the highest Christian doctrine in this passage, we have at least the
solution of the enigma of the origin of life, in the revealed truth
that it was caused by the Creative Spirit.
_From the_ RECORD, _Sept._ 23, 1870.
_Discovery of Motives, No. I._--But why did Professor Tyndall make
such an appeal to the imagination of his hearers? His imaginary picture
of the occult operations of light was introduced as a plea for the
wildness of such weaker brethren, as he calls Mr. Darwin, in speaking
of his theory of natural selection, succeeded by his supplementary
theory of pangenesis. It is objected to Mr. Darwin’s theories by
Christian philosophers that these theories are essentially atheistic.
That they are framed for the express purpose of blotting out of the
page of nature some of the most marvellous evidences of design--of
the most patent revelations of the book of nature, that there is an
all-wise, all-mighty Creator, God. That these theories deprive man of
all those prerogatives that raise him above the brute. That the facts
of nature contradict them. The first theory of Mr. Darwin, that of
natural selection, is an attempt to account for the formation of all
animal and vegetable beings from an hypothetical germ.... Even this
does not pall the imagination of Professor Tyndall. He accepts the
theory of the avowed atheist Louis Buchner, in his ‘Force and Matter,’
that the theory of evolution requires us to imagine not only that all
the structures, animal and vegetable, were once potentially present
in the fire-mist of the nebulous theory, but also that all mental
powers--Plato, Shakespeare, Newton, and Raphael--are potential in the
fires of the sun.
Professor Tyndall appeals to believers in the Bible as God’s Word not
to style such a theory wicked or impious. He says men can hold it, and
manifest in their lives what he terms so-called Christian virtues. He
says, ‘They who keep such questions open and will not tolerate any
unlawful limitation of the horizon of their souls, have as little
fellowship with the atheist who says there is no God, as with the
theist who professes to know the mind of God.’ These men then are
theists, but what kind of a God does their free speculation require?
The theists who are sneered at by Professor Tyndall, who believe in a
God who has revealed his will and his mind to man, have far higher and
more convincing proofs that He has so revealed Himself than Professor
Tyndall can ever accumulate for his belief in the undulatory theory of
light.
Professor Tyndall’s philosophy regards the universe as a huge
mechanical, self-supporting, self-sustaining, self-evolving, material
machine--untended by a loving Father’s sustaining and providential
care. His God is the God of the Epicureans, who created and started
the machine into motion and then left it for ever to itself. Such a
philosophy, the child of unbridled pride of intellect, may appeal
to the wildest imagination of corrupted human nature, but it has no
sympathy with all the higher yearnings of the soul.
_From the_ LANCET, _Sept._ 24, 1870.
_Discovery of Motives, No II._--Now, Professor Tyndall’s object
was to preach about germs, and he proceeded to accomplish it in
somewhat the following manner. He first set forth that it was a
wholesome use of the imagination to apply our knowledge of aërial
sound-waves to the solution of the question--what is the cause of
the phenomena of light? And he then proceeded to draw one of those
charming word-pictures for which he is so famous, showing the rippling
of the ethereal light-waves against molecules in the atmosphere, the
greater proportionate reflection of the shorter wave of blue, and the
consequent preponderance of blue rays in the light reflected to us from
the sky, and of red and yellow rays in the light coming unreflected
from the sun.... Now, the aim of all this was to seek and show that
the air is filled by an infinite multitude of suspended particles, so
minute that they do not produce darkness, and that these particles
may be germs. Professor Tyndall does not say that they are germs,
but, by the aid of a special disclaimer, he prevented his audience
from forgetting that they might be. We should be very loth to accuse
him of disingenuousness, but we are unable entirely to acquit him of
special pleading. We feel that his lecture was a very skilful attempt
to familiarise the public mind with the existence of atmospheric
particles, and to lead up to and encourage, without absolutely
expressing the idea that germs are particles, and that particles may be
germs.
_To the Editor of the_ RECORD.
SIR,--It is a grave error on your part to represent me as
calling Mr. Darwin ‘one of the weaker brethren.’ Were I asked to name
the highest representative of the stronger ones, I should probably name
him. But in your article you link my name with that of a writer whom I
do rank among the weaker brethren; weak through a defect common to him
and his antagonists--the incompetence, namely, to look round a great
question and see its bearings on all sides.
I am, Sir, your obedient servant,
JOHN TYNDALL.
ATHENÆUM CLUB, October 4.
_From the_ PALL MALL GAZETTE, _September_ 20, 1870.
Why does Professor Tyndall attribute to Goethe the ‘notion,’ as he
calls it, that matter is ‘the living garment of God’? We are not aware
that it is to be found in his works. In ‘Faust’ Goethe introduces the
spirit of the earth, who describes his own operations as consisting in
weaving into one vast fabric the ‘tumults of human life, the storm of
actions,’ births and deaths, and the affairs of us mortals, and working
thereout ‘a living garment for the Divinity.’ Whether the phrase be
a piece of cant, or a piece of sublimity, it has no semblance of the
meaning which the Professor attributes to it.
_From the_ SPECTATOR, _September_ 24, 1870.
Professor Tyndall concluded his lecture by a passage on the development
theory, in which he contended that if our traditional view of matter
had been Goethe’s view, that matter is ‘the living garment of God,’
instead of Young’s, who looked upon it as foreign to mind, and taking
all its laws from outside itself, the development theory would not seem
to us what we now mean by materialistic. The ‘Pall Mall’ falls severely
on Professor Tyndall for misquoting Goethe, and shows that the passage
in ‘Faust’ probably referred to, where the Erdgeist speaks of weaving
a ‘living garment for the Divinity,’ did not refer to external nature
at all. No doubt the special quotation was a little wide of the mark,
but does the critic in the ‘Pall Mall’ doubt that Professor Tyndall
was interpreting quite accurately Goethe’s conception, as elsewhere
expressed with sufficient elaboration? If he does not, his criticism
is a cavil. If he does, let him study Goethe more thoroughly--‘Gott
und Welt,’ for example, of the proem to which a friend has sent us a
faithful version to-day, which we print in another column. What can be
stronger than this?--
Was wär’ ein Gott der nur von aussen stiesse
Im Kreis das All am Finger laufen liesse!
Ihm ziemt’s, die Welt im Innern zu bewegen,
Natur in Sich, Sich in Natur zu hegen.
_A Translation of Goethe’s Proemium to ‘Gott und Welt.’_
To Him who from eternity, self-stirred,
Himself hath made by His creative Word!
To him, supreme, who causeth Faith to be,
Trust, Hope, Love, Power, and endless Energy!
To Him, who, seek to name Him as we will,
Unknown within Himself abideth still!
Strain ear and eye, till sight and sense be dim;
Thou’lt find but faint similitudes of Him:
Yea, and thy spirit in her flight of flame
Still strives to gauge the symbol and the name:
Charmed and compelled thou climb’st from height to height,
And round thy path the world shines wondrous bright;
Time, Space, and Size, and Distance cease to be,
And every step is fresh infinity.
What were the God who sat outside to scan
The spheres that ’neath his finger circling ran?
God dwells within, and moves the world and moulds,
Himself and Nature in one form enfolds:
Thus all that lives in Him and breathes and is,
Shall ne’er His puissance, ne’er His spirit miss.
The soul of man, too, is an universe:
Whence follows it that race with race concurs
In naming all it knows of good and true
God,--yea, its own God; and with homage due
Surrenders to His sway both earth and heaven;
Fears Him, and loves, where place for love is given.
J. A. S.
From the SPECTATOR, September 24.
_From the_ TIMES, _October_ 3, 1870.
But the most serious obstacle of a public nature which can possibly
impede the progress of science--an obstacle before which all others
sink into absolute insignificance--is _the reign of prejudice_,
or the unwillingness to adopt the teachings of science, and to accept
her legitimate conclusions through certain preconceived opinions,
the result of a faulty education or a vicious temperament. To this,
indeed, we think the British Association cannot pay too much attention,
and we were not a little gratified, in consequence, at the eloquent
lecture on the use of the imagination in science delivered by Professor
Tyndall. The importance of such a discourse at such a time to clear
the atmosphere of the clouds of prejudice which a mistaken zeal has
raised in the minds of a large class cannot be over-estimated. Since
it is certain that religious intolerance and religious bigotry are
the largest sources of prejudice, the removal of these ought to be a
primary object of the association, and when the undertaking is made
with the same spirit of reverence, the same earnestness of purpose, and
philosophical acumen which distinguished Professor Tyndall’s discourse,
it seems impossible to doubt that much benefit must ultimately result
thereby to the cause of truth. The impression produced on our minds
by that philosophical masterpiece will not be easily effaced. As
we listened in that crowded hall with admiration to the thoughtful
investigator who was unfolding to us the workings of a mind much more
than ordinarily acute, we pictured to ourselves the effect which
it was so well calculated to produce in the mind of the sceptic in
science. We saw in imagination the victory of conscience and reason,
the emancipation of a soul, the new birth of an intelligence. As the
speaker welded one link to another of the long chain of ratiocination,
his ardour rising with the progress of his argument, we thought that it
had never been our good fortune to listen to so splendid a discourse.
But the end was not yet. The grand appeal had still to be made. In a
magnificent peroration Professor Tyndall concluded an argument of no
common order--an argument not fitted, indeed, to assuage the terrors
of a vicious imagination; an argument which may perchance have grated
harshly on the sacerdotal ear; but an argument which elicited thunders
of applause from an audience more than usually critical--with an appeal
of unrivalled eloquence to abandon dogmatism for ever, and fairly bring
every hypothesis before the bar of a disciplined reason. The place and
the people were worthy of the man. In a vast hall whose name recalls
the finest relics of the old English ballad were gathered together all
that the most populous and intelligent shire of Britain could produce
of talent and influence, while grouped around the presidential chair
were many of the most brilliant ornaments of British science and the
representatives of foreign philosophy. It may, indeed, be surmised
that of the three thousand souls who listened to Professor Tyndall’s
lay sermon there were few who entered into the discussion prepared to
embrace his views. Yet we think that there were few also who left that
hall at all events without a doubt that the search after truth which is
the sole object of the investigation of nature is neither so prosaic
nor so dangerous a quest as the false prophets and the Philistines
would assert--that philosophy is not ‘harsh and crabbed as dull fools
suppose’--
But musical as is Apollo’s lute,
And a perpetual feast of nectar’d sweets,
Where no crude surfeit reigns.
SCIENTIFIC USE OF THE IMAGINATION.
[Illustration]
I CARRIED with me to the Alps this year the heavy burden of this
evening’s work. In the way of new investigation I had nothing complete
enough to be brought before you; so all that remained to me was to fall
back upon such residues as I could find in the depths of consciousness,
and out of them to spin the fibre and weave the web of this discourse.
Save from memory I had no direct aid upon the mountains; but to spur
up the emotions, on which so much depends, as well as to nourish
indirectly the intellect and will, I took with me two volumes of
poetry, Goethe’s ‘Farbenlehre,’ and the work on ‘Logic’ recently
published by Mr. Alexander Bain.[1] The spur, I am sorry to say, was
no match for the integument of dulness it had to pierce. In Goethe,
so glorious otherwise, I chiefly noticed the self-inflicted hurts of
genius, as it broke itself in vain against the philosophy of Newton.
For a time, Mr. Bain became my principal companion. I found him learned
and practical, shining generally with a dry light, but exhibiting at
times a flush of emotional strength, which proved that even logicians
share the common fire of humanity. He interested me most when he
became the mirror of my own condition. Neither intellectually nor
socially is it good for man to be alone, and the griefs of thought are
more patiently borne when we find that they have been experienced by
another. From certain passages in his book I could infer that Mr. Bain
was no stranger to such sorrows. Take this passage as an illustration.
Speaking of the ebb of intellectual force, which we all from time to
time experience, Mr. Bain says, ‘The uncertainty where to look for the
next opening of discovery brings the pain of conflict and the debility
of indecision.’ These words have in them the true ring of personal
experience. The action of the investigator is periodic. He grapples
with a subject of enquiry, wrestles with it, overcomes it, exhausts, it
may be, both himself and it for the time being. He breathes a space,
and then renews the struggle in another field. Now this period of
halting between two investigations is not always one of pure repose.
It is often a period of doubt and discomfort, of gloom and ennui. ‘The
uncertainty where to look for the next opening of discovery brings the
pain of conflict and the debility of indecision.’ Such was my precise
condition in the Alps this year; in a score of words Mr. Bain has here
sketched my mental diagnosis; and it was under these evil circumstances
that I had to equip myself for the hour and the ordeal that are now
come.
Gladly, however, as I should have seen this duty in other hands, I
could by no means shrink from it. Disloyalty would have been worse
than failure. In some fashion or other--feebly or strongly, meanly
or manfully, on the higher levels of thought, or on the flats of
common-place,--the task had to be accomplished. I looked in various
directions for help and furtherance; but without me for a time I saw
only ‘antres vast,’ and within me ‘deserts idle.’ My case resembled
that of a sick doctor who had forgotten his art and sorely needed the
prescription of a friend. Mr. Bain wrote one for me. He said, ‘Your
present knowledge must forge the links of connection between what has
been already achieved and what is now required.’[2] In these words
he admonished me to review the past and recover from it the broken
ends of former investigations. I tried to do so. Previous to going to
Switzerland I had been thinking much of light and heat, of magnetism
and electricity, of organic germs, atoms, molecules, spontaneous
generation, comets, and skies. With one or another of these I now
sought to re-form an alliance, and finally succeeded in establishing a
kind of cohesion between thought and Light. The wish grew within me to
trace, and to enable you to trace, some of the more occult operations
of this agent. I wished, if possible, to take you behind the drop-scene
of the senses, and to show you the hidden mechanism of optical action.
For I take it to be well worth the while of the scientific teacher to
take some pains, and even great pains, to make those whom he addresses
copartners of his thoughts. To clear his own mind in the first place
from all haze and vagueness, and then to project into language which
shall leave no mistake as to his meaning--which shall leave even his
errors naked--the definite ideas he has shaped. A great deal is, I
think, possible to scientific exposition conducted in this way. It
is possible, I believe, even before an audience like the present, to
uncover to some extent the unseen things of nature; and thus to give,
not only to professed students, but to others with the necessary bias,
industry, and capacity, an intelligent interest in the operations of
science. Time and labour are necessary to this result, but science is
the gainer from the public sympathy thus created.
How then are those hidden things to be revealed? How, for example,
are we to lay hold of the physical basis of light, since, like that
of life itself, it lies entirely without the domain of the senses?
Now philosophers may be right in affirming that we cannot transcend
experience. But we can, at all events, carry it a long way from
its origin. We can also magnify, diminish, qualify, and combine
experiences, so as to render them fit for purposes entirely new. We are
gifted with the power of Imagination,--combining what the Germans call
Anschauungsgabe and Einbildungskraft--and by this power we can lighten
the darkness which surrounds the world of the senses. There are tories
even in science who regard imagination as a faculty to be feared and
avoided rather than employed. They had observed its action in weak
vessels and were unduly impressed by its disasters. But they might with
equal justice point to exploded boilers as an argument against the use
of steam. Bounded and conditioned by cooperant Reason, imagination
becomes the mightiest instrument of the physical discoverer. Newton’s
passage from a falling apple to a falling moon was, at the outset,
a leap of the imagination. When William Thomson tries to place the
ultimate particles of matter between his compass points, and to apply
to them a scale of millimetres, he is powerfully aided by this faculty.
And in much that has been recently said about protoplasm and life, we
have the outgoings of the imagination guided and controlled by the
known analogies of science. In fact, without this power, our knowledge
of nature would be a mere tabulation of coexistences and sequences. We
should still believe in the succession of day and night, of summer and
winter; but the soul of Force would be dislodged from our universe;
causal relations would disappear, and with them that science which is
now binding the parts of nature to an organic whole.
I should like to illustrate by a few simple instances the use that
scientific men have already made of this power of imagination, and to
indicate afterwards some of the further uses that they are likely to
make of it. Let us begin with the rudimentary experiences. Observe
the falling of heavy rain-drops into a tranquil pond. Each drop as
it strikes the water becomes a centre of disturbance, from which a
series of ring-ripples expand outwards. Gravity and inertia are the
agents by which this wave-motion is produced, and a rough experiment
will suffice to show that the rate of propagation does not amount to
a foot a second. A series of slight mechanical shocks is experienced
by a body plunged in the water as the wavelets reach it in succession.
But a finer motion is at the same time set up and propagated. If
the head and ears be immersed in the water, as in an experiment of
Franklin’s, the shock of the drop is communicated to the auditory
nerve--the _tick_ of the drop is heard. Now this sonorous impulse
is propagated, not at the rate of a foot a second, but at the rate
of 4,700 feet a second. In this case it is not the gravity, but
the _elasticity_ of the water that is the urging force. Every
liquid particle pushed against its neighbour delivers up its motion
with extreme rapidity, and the pulse is propagated as a thrill. The
incompressibility of water, as illustrated by the famous Florentine
experiment, is a measure of its elasticity, and to the possession
of this property in so high a degree the rapid transmission of a
sound-pulse through water is to be ascribed.
But water, as you know, is not necessary to the conduction of sound;
air is its most common vehicle. And you know that when the air
possesses the particular density and elasticity corresponding to the
temperature of freezing water the velocity of sound in it is 1,090
feet a second. It is almost exactly one-fourth of the velocity in
water; the reason being that though the greater weight of the water
tends to diminish the velocity, the enormous molecular elasticity of
the liquid far more than atones for the disadvantage due to weight. By
various contrivances we can compel the vibrations of the air to declare
themselves; we know the length and frequency of sonorous waves, and
we have also obtained great mastery over the various methods by which
the air is thrown into vibration. We know the phenomena and laws of
vibrating rods, of organ-pipes, strings, membranes, plates, and bells.
We can abolish one sound by another. We know the physical meaning of
music and noise, of harmony and discord. In short, as regards sound
we have a very clear notion of the external physical processes which
correspond to our sensations.
In these phenomena of sound we travel a very little way from downright
sensible experience. Still the imagination is to some extent exercised.
The bodily eye, for example, cannot see the condensations and
rarefactions of the waves of sound. We construct them in thought, and
we believe as firmly in their existence as in that of the air itself.
But now our experience has to be carried into a new region, where a new
use is to be made of it. Having mastered the cause and mechanism of
sound, we desire to know the cause and mechanism of light. We wish to
extend our enquiries from the auditory nerve to the optic nerve. Now
there is in the human intellect a power of expansion--I might almost
call it a power of creation--which is brought into play by the simple
brooding upon facts. The legend of the Spirit brooding over chaos may
have originated in a knowledge of this power. In the case now before us
it has manifested itself by transplanting into space, for the purposes
of light, an adequately modified form of the mechanism of sound. We
know intimately whereon the velocity of sound depends. When we lessen
the density of a medium and preserve its elasticity constant we augment
the velocity. When we heighten the elasticity and keep the density
constant we also augment the velocity. A small density, therefore, and
a great elasticity, are the two things necessary to rapid propagation.
Now light is known to move with the astounding velocity of 185,000
miles a second. How is such a velocity to be obtained? By boldly
diffusing in space a medium of the requisite tenuity and elasticity.
Let us make such a medium our starting point, endowing it with one or
two other necessary qualities; let us handle it in accordance with
strict mechanical laws; give to every step of our deduction the surety
of the syllogism; carry it thus forth from the world of imagination
to the world of sense, and see whether the final outcrop of the
deduction be not the very phenomena of light which ordinary knowledge
and skilled experiment reveal. If in all the multiplied varieties of
these phenomena, including those of the most remote and entangled
description, this fundamental conception always brings us face to face
with the truth; if no contradiction to our deductions from it be found
in external nature, but on all sides agreement and verification; if,
moreover, as in the case of Conical Refraction and in other cases,
it has actually forced upon our attention phenomena which no eye had
previously seen, and which no mind had previously imagined, such a
conception, which never disappoints us, but always lands us on the
solid shores of fact, must, we think, be something more than a mere
figment of the scientific fancy. In forming it that composite and
creative unity in which reason and imagination are together blent,
has, we believe, led us into a world not less real than that of the
senses, and of which the world of sense itself is the suggestion and
justification.
Far be it from me, however, to wish to fix you immovably in this or
in any other theoretic conception. With all our belief of it, it will
be well to keep the theory plastic and capable of change. You may,
moreover, urge that although the phenomena occur _as if_ the
medium existed, the absolute demonstration of its existence is still
wanting. Far be it from me to deny to this reasoning such validity
as it may fairly claim. Let us endeavour by means of analogy to form
a fair estimate of its force. You believe that in society you are
surrounded by reasonable beings like yourself. You are perhaps as
firmly convinced of this as of anything. What is your warrant for
this conviction? Simply and solely this, your fellow-creatures behave
as if they were reasonable; the hypothesis, for it is nothing more,
accounts for the facts. To take an eminent example: you believe that
our President is a reasonable being. Why? There is no known method of
superposition by which any one of us can apply himself intellectually
to another so as to demonstrate coincidence as regards the possession
of reason. If, therefore, you hold our President to be reasonable, it
is because he behaves _as if_ he were reasonable. As in the case
of the ether, beyond the ‘_as if_’ you cannot go. Nay I should not
wonder if a close comparison of the data on which both inferences rest,
caused many respectable persons to conclude that the ether had the best
of it.
This universal medium, this light-ether as it is called, is a vehicle,
not an origin of wave-motion. It receives and transmits, but it does
not create. Whence does it derive the motions it conveys? For the
most part from luminous bodies. By this motion of a luminous body I do
not mean its sensible motion, such as the flicker of a candle, or the
shooting out of red prominences from the limb of the sun. I mean an
intestine motion of the atoms or molecules of the luminous body. But
here a certain reserve is necessary. Many chemists of the present day
refuse to speak of atoms and molecules as real things. Their caution
leads them to stop short of the clear, sharp, mechanically intelligible
atomic theory enunciated by Dalton, or any form of that theory, and to
make the doctrine of multiple proportions their intellectual bourne. I
respect the caution, though I think it is here misplaced. The chemists
who recoil from these notions of atoms and molecules accept without
hesitation the Undulatory Theory of Light. Like you and me they one and
all believe in an ether and its light producing waves. Let us consider
what this belief involves. Bring your imaginations once more into play
and figure a series of sound-waves passing through air. Follow them
up to their origin, and what do you there find? A definite, tangible,
vibrating body. It may be the vocal chords of a human being, it may
be an organ-pipe, or it may be a stretched string. Follow in the same
manner a train of ether waves to their source; remembering at the same
time that your ether is matter, dense, elastic, and capable of motions
subject to and determined by mechanical laws. What then do you expect
to find as the source of a series of ether waves? Ask your imagination
if it will accept a vibrating multiple proportion--a numerical ratio in
a state of oscillation? I do not think it will. You cannot crown the
edifice by this abstraction. The scientific imagination, which is here
authoritative, demands as the origin and cause of a series of ether
waves a particle of vibrating matter quite as definite, though it may
be excessively minute, as that which gives origin to a musical sound.
Such a particle we name an atom or a molecule. I think the seeking
intellect when focussed so as to give definition without penumbral
haze, is sure to realise this image at the last.
To preserve thought continuous throughout this discourse, to prevent
either lack of knowledge or failure of memory from producing any rent
in our picture, I here propose to run rapidly over a bit of ground
which is probably familiar to most of you, but which I am anxious
to make familiar to you all. The waves generated in the ether by
the swinging atoms of luminous bodies are of different lengths and
amplitudes. The amplitude is the width of swing of the individual
particles of the wave. In water-waves it is the height of the crest
above the trough, while the length of the wave is the distance between
two consecutive crests. The aggregate of waves emitted by the sun may
be broadly divided into two classes: the one class competent, the
other incompetent, to excite vision. But the light-producing waves
differ markedly among themselves in size, form, and force. The length
of the largest of these waves is about twice that of the smallest,
but the amplitude of the largest is probably a hundred times that of
the smallest. Now the force or energy of the wave, which, expressed
with reference to sensation, means the intensity of the light, is
proportional to the square of the amplitude. Hence the amplitude being
one-hundredfold, the energy of the largest light-giving waves would
be ten-thousandfold that of the smallest. This is not improbable. I
use these figures not with a view to numerical accuracy, but to give
you definite ideas of the differences that probably exist among the
light-giving waves. And if we take the whole range of solar radiation
into account--its non-visual as well as its visual waves--I think it
probable that the force or energy of the largest wave is a million
times that of the smallest.
Turned into their equivalents of sensation, the different light-waves
produce different colours. Red, for example, is produced by the largest
waves, violet by the smallest, while green is produced by a wave of
intermediate length and amplitude. On entering from air into more
highly refracting substances, such as glass or water, or the sulphide
of carbon, all the waves are retarded, but the smallest ones most.
This furnishes a means of separating the different classes of waves
from each other; in other words, of analysing the light. Sent through
a refracting prism, the waves of the sun are turned aside in different
degrees from their direct course, the red least, the violet most.
They are virtually pulled asunder, and they paint upon a white screen
placed to receive them ‘the solar spectrum.’ Strictly speaking, the
spectrum embraces an infinity of colours, but the limits of language
and of our powers of distinction cause it to be divided into seven
segments: red, orange, yellow, green, blue, indigo, violet. These
are the seven primary or prismatic colours. Separately, or mixed in
various proportions, the solar waves yield all the colours observed in
nature and employed in art. Collectively, they give us the impression
of whiteness. Pure unsifted solar light is white; and if all the
wave-constituents of such light be reduced in the same proportion,
the light, though diminished in intensity, will still be white. The
whiteness of Alpine snow with the sun shining upon it, is barely
tolerable to the eye. The same snow under an overcast firmament is
still white. Such a firmament enfeebles the light by reflection, and
when we lift ourselves above a cloud-field--to an Alpine summit, for
instance, or to the top of Snowdon--and see, in the proper direction,
the sun shining on the clouds, they appear dazzlingly white. Ordinary
clouds, in fact, divide the solar light impinging on them into two
parts--a reflected part and a transmitted part, in each of which the
proportions of wave-motion which produce the impression of whiteness
are sensibly preserved.
It will be understood that the conditions of whiteness would fail if
all the waves were diminished _equally_, or by the same absolute
quantity. They must be reduced _proportionately_, instead of
equally. If by the act of reflexion the waves of red light are split
into exact halves, then, to preserve the light white, the waves
of yellow, orange, green, and blue must also be split into exact
halves. In short, the reduction must take place, not by absolutely
equal quantities, but by equal fractional parts. In white light the
preponderance as regards energy of the larger over the smaller waves
must always be immense. Were the case otherwise, the physiological
correlative, _blue_, of the smaller waves would have the upper
hand in our sensations.
My wish to render our mental images complete, causes me to dwell
briefly upon these known points, and the same wish will cause me to
linger a little longer among others. But here I am disturbed by my
reflections. When I consider the effect of dinner upon the nervous
system, and the relation of that system to the intellectual powers
I am now invoking--when I remember that the universal experience of
mankind has fixed upon certain definite elements of perfection in
an after-dinner speech, and when I think how conspicuous by their
absence these elements are on the present occasion, the thought is not
comforting to a man who wishes to stand well with his fellow-creatures
in general, and with the members of the British Association in
particular. My condition might well resemble that of the ether, which
is scientifically defined as an assemblage of vibrations. And the
worst of it is that unless you reverse the general verdict regarding
the effect of dinner, and prove in your own persons that a uniform
experience need not continue uniform--which will be a great point
gained for some people--these tremors of mine are likely to become
more and more painful. But I call to mind the comforting words of an
inspired though uncanonical writer, who admonishes us in the Apocrypha
that fear is a bad counsellor. Let me then cast him out, and let me
trustfully assume that you will one and all postpone that balmy sleep,
of which dinner might under the circumstances be regarded as the
indissoluble antecedent, and that you will manfully and womanfully
prolong your investigations of the ether and its waves into regions
which have been hitherto crossed by the pioneers of science alone.
Not only are the waves of ether reflected by clouds, by solids, and
by liquids, but when they pass from light air to dense, or from dense
air to light, a portion of the wave-motion is always reflected. Now
our atmosphere changes continually in density from top to bottom. It
will help our conceptions if we regard it as made up of a series of
thin concentric layers, or shells of air, each shell being of the
same density throughout, and a small and sudden change of density
occurring in passing from shell to shell. Light would be reflected at
the limiting surfaces of all these shells, and their action would be
practically the same as that of the real atmosphere. And now I would
ask your imagination to picture this act of reflection. What must
become of the reflected light? The atmospheric layers turn their convex
surfaces towards the sun, they are so many convex mirrors of feeble
power, and you will immediately perceive that the light regularly
reflected from these surfaces cannot reach the earth at all, but is
dispersed in space.
But though the sun’s light is not reflected in this fashion from the
aërial layers to the earth, there is indubitable evidence to show that
the light of our firmament is reflected light. Proofs of the most
cogent description could be here adduced; but we need only consider
that we receive light at the same time from all parts of the hemisphere
of heaven. The light of the firmament comes to us across the direction
of the solar rays, and even against the direction of the solar rays;
and this lateral and opposing rush of wave-motion can only be due
to the rebound of the waves from the air itself, or from something
suspended in the air. It is also evident that, unlike the action of
clouds, the solar light is not reflected by the sky in the proportions
which produce white. The sky is blue, which indicates a deficiency
on the part of the larger waves. In accounting for the colour of the
sky, the first question suggested by analogy would undoubtedly be, is
not the air blue? The blueness of the air has in fact been given as
a solution of the blueness of the sky. But reason basing itself on
observation, asks in reply, How, if the air be blue, can the light
of sunrise and sunset, which travels through vast distances of air,
be yellow, orange, or even red? The passage of the white solar light
through a blue medium could by no possibility redden the light. The
hypothesis of a blue air is therefore untenable. In fact the agent,
whatever it is, which sends us the light of the sky, exercises in so
doing a dichroitic action. The light reflected is blue, the light
transmitted is orange or red. A marked distinction is thus exhibited
between the matter of the sky and that of an ordinary cloud, which
latter exercises no such dichroitic action.
By the force of imagination and reason combined we may penetrate this
mystery also. The cloud takes no note of size on the part of the waves
of ether, but reflects them all alike. It exercises no selective
action. Now the cause of this may be that the cloud particles are so
large in comparison with the size of the waves of ether as to reflect
them all indifferently. A broad cliff reflects an Atlantic roller as
easily as a ripple produced by a sea-bird’s wing; and in the presence
of large reflecting surfaces, the existing differences of magnitude
among the waves of ether may disappear. But supposing the reflecting
particles, instead of being very large, to be very small, in comparison
with the size of the waves. In this case, instead of the whole wave
being fronted and in great part thrown back, a small portion only is
shivered off. The great mass of the wave passes over such a particle
without reflection. Scatter then a handful of such minute foreign
particles in our atmosphere, and set imagination to watch their action
upon the solar waves. Waves of all sizes impinge upon the particles,
and you see at every collision a portion of the impinging wave struck
off by reflection. All the waves of the spectrum, from the extreme red
to the extreme violet, are thus acted upon. But in what proportions
will the waves be scattered? A clear picture will enable us to
anticipate the experimental answer. Remembering that the red waves are
to the blue much in the relation of billows to ripples, let us consider
whether those extremely small particles are competent to scatter
all the waves in the same proportion. If they be not--and a little
reflection will make it clear to you that they are not--the production
of colour must be an incident of the scattering. Largeness is a thing
of relation; and the smaller the wave, the greater is the relative
size of any particle on which the wave impinges, and the greater also
the ratio of the reflected portion to the total wave. A pebble placed
in the way of the ring-ripples produced by our heavy rain-drops on a
tranquil pond will throw back a large fraction of the ripple incident
upon it, while the fractional part of a larger wave thrown back by the
same pebble might be infinitesimal. Now we have already made it clear
to our minds that to preserve the solar light white, its constituent
proportions must not be altered; but in the act of division performed
by these very small particles we see that the proportions are altered;
an undue fraction of the smaller waves is scattered by the particles,
and, as a consequence, in the scattered light, blue will be the
predominant colour. The other colours of the spectrum must, to some
extent, be associated with the blue. They are not absent but deficient.
We ought, in fact, to have them all, but in diminishing proportions,
from the violet to the red.
We have here presented a case to the imagination, and, assuming the
undulatory theory to be a reality, we have, I think, fairly reasoned
our way to the conclusion, that were particles, small in comparison
to the size of the ether waves, sown in our atmosphere, the light
scattered by those particles would be exactly such as we observe in
our azure skies. When this light is analysed, all the colours of the
spectrum are found; but they are found in the proportions indicated by
our conclusion.
Let us now turn our attention to the light which passes unscattered
among the particles. How must it be finally affected? By its successive
collisions with the particles the white light is more and more robbed
of its shorter waves; it therefore loses more and more of its due
proportion of blue. The result may be anticipated. The transmitted
light, where short distances are involved, will appear yellowish.
But as the sun sinks towards the horizon the atmospheric distances
increase, and consequently the number of the scattering particles.
They abstract in succession the violet, the indigo, the blue, and even
disturb the proportions of green. The transmitted light under such
circumstances must pass from yellow through orange to red. This also is
exactly what we find in nature. Thus, while the reflected light gives
us at noon the deep azure of the Alpine skies, the transmitted light
gives us at sunset the warm crimson of the Alpine snows. The phenomena
certainly occur _as if_ our atmosphere were a medium rendered
slightly turbid by the mechanical suspension of exceedingly small
foreign particles.
Here, as before, we encounter our sceptical ‘_as if_.’ It is
one of the parasites of science, ever at hand, and ready to plant
itself and sprout, if it can, on the weak points of our philosophy.
But a strong constitution defies the parasite, and in our case, as we
question the phenomena, probability grows like growing health, until
in the end the malady of doubt is completely extirpated. The first
question that naturally arises is--Can small particles be really
proved to act in the manner indicated? No doubt of it. Each one of
you can submit the question to an experimental test. Water will not
dissolve resin, but spirit will; and when spirit which holds resin in
solution is dropped into water, the resin immediately separates in
solid particles, which render the water milky. The coarseness of this
precipitate depends on the quantity of the dissolved resin. You can
cause it to separate in thick clots or in exceedingly fine particles.
Professor Brücke has given us the proportions which produce particles
particularly suited to our present purpose. One gramme of clean mastic
is dissolved in eighty-seven grammes of absolute alcohol, and the
transparent solution is allowed to drop into a beaker containing clear
water kept briskly stirred. An exceedingly fine precipitate is thus
formed, which declares its presence by its action upon light. Placing a
dark surface behind the beaker, and permitting the light to fall into
it from the top or front, the medium is seen to be distinctly blue. It
is not perhaps so perfect a blue as I have seen on exceptional days,
this year, among the Alps, but it is a very fair sky-blue. A trace of
soap in water gives a tint of blue. London, and I fear Liverpool milk,
makes an approximation to the same colour through the operation of the
same cause; and Helmholtz has irreverently disclosed the fact that a
blue eye is simply a turbid medium.
The action of turbid media upon light was illustrated by Goethe,
who, though unacquainted with the undulatory theory, was led by his
experiments to regard the firmament as an illuminated turbid medium
with the darkness of space behind it. He describes glasses showing a
bright yellow by transmitted, and a beautiful blue by reflected light.
Professor Stokes, who was probably the first to discern the real nature
of the action of small particles on the waves of ether, describes a
glass of a similar kind.[3] Capital specimens of such glass are to be
found at Salviati’s in St. James’s Street. What artists call ‘chill’ is
no doubt an effect of this description. Through the action of minute
particles, the browns of a picture often present the appearance of
the bloom of a plum. By rubbing the varnish with a silk handkerchief
optical continuity is established, and the chill disappears. Some
years ago I witnessed Mr. Hirst experimenting at Zermatt on the turbid
water of the Visp, which was charged with the finely divided matter
ground down by the glaciers. When kept still for a day or so, the
grosser matter sank, but the finer matter remained suspended, and gave
a distinctly blue tinge to the water. The blueness of certain Alpine
lakes has been shown to be in part due to this cause. Prof. Roscoe has
noticed several striking cases of a similar kind. In a very remarkable
paper the late Principal Forbes showed that steam issuing from the
safety-valve of a locomotive, when favourably observed, exhibits at a
certain stage of its condensation the colours of the sky. It is blue by
reflected light, and orange or red by transmitted light. The effect,
as pointed out by Goethe, is to some extent exhibited by peat smoke.
More than ten years ago I amused myself at Killarney by observing on
a calm day the straight smoke-columns rising from the chimneys of the
cabins. It was easy to project the lower portion of a column against a
dark pine, and its upper portion against a bright cloud. The smoke in
the former case was blue, being seen mainly by reflected light; in the
latter case it was reddish, being seen mainly by transmitted light.
Such smoke was not in exactly the condition to give us the glow of the
Alps, but it was a step in this direction. Brücke’s fine precipitate
above referred to looks yellowish by transmitted light, but by duly
strengthening the precipitate you may render the white light of noon
as ruby-coloured as the sun when seen through Liverpool smoke, or upon
Alpine horizons. I do not, however, point to the gross smoke arising
from coal as an illustration of the action of small particles, because
such smoke soon absorbs and destroys the waves of blue instead of
sending them to the eyes of the observer.
These multifarious facts, and numberless others which cannot now be
referred to, are explained by reference to the single principle, that
where the scattering particles are small in comparison to the size
of the waves we have in the reflected light a greater proportion of
the smaller waves, and in the transmitted light a greater proportion
of the larger waves, than existed in the original white light. The
physiological consequence is that in the one light blue is predominant,
and in the other light orange or red. And now let us push our enquiries
forward. Our best microscopes can readily reveal objects not more than
¹⁄₅₀₀₀₀th of an inch in diameter. This is less than the length of a
wave of red light. Indeed a first-rate microscope would enable us to
discern objects not exceeding in diameter the length of the smallest
waves of the visible spectrum. By the microscope therefore we can
submit our particles to an experimental test. If they are as large as
the light-waves they will infallibly be seen; and if they are not seen
it is because they are smaller. I placed in the hands of our President
a bottle containing Brücke’s particles in greater number and coarseness
than those examined by Brücke himself. The liquid was a milky blue, and
Mr. Huxley applied to it his highest microscopic power. He satisfied
me at the time that had particles of even ¹⁄₁₀₀₀₀₀th of an inch in
diameter existed in the liquid they could not have escaped detection.
But no particles were seen. Under the microscope the turbid liquid was
not to be distinguished from distilled water. Brücke, I may say, also
found the particles to be of ultra-microscopic magnitude.
But we have it in our power to imitate far more closely than we have
hitherto done the natural conditions of this problem. We can generate
in air, as many of you know, artificial skies, and prove their perfect
identity with the natural one, as regards the exhibition of a number
of wholly unexpected phenomena. By a continuous process of growth
moreover we are able to connect sky-matter, if I may use the term,
with molecular matter on the one side, and with molar matter, or
matter in sensible masses, on the other. In illustration of this, I
will take an experiment described by M. Morren of Marseilles at the
last meeting of the British Association. Sulphur and oxygen combine to
form sulphurous acid gas. It is this choking gas that is smelt when a
sulphur match is burnt in air. Two atoms of oxygen and one of sulphur
constitute the molecule of sulphurous acid. Now it has been recently
shown in a great number of instances that waves of ether issuing from
a strong source, such as the sun or the electric light, are competent
to shake asunder the atoms of gaseous molecules. A chemist would call
this ‘decomposition’ by light; but it behoves us, who are examining
the power and function of the imagination, to keep constantly before
us the physical images which we hold to underlie our terms. Therefore
I say, sharply and definitely, that the components of the molecules
of sulphurous acid are shaken asunder by the ether waves. Enclosing
the substance in a suitable vessel, placing it in a dark room, and
sending through it a powerful beam of light, we at first see nothing:
the vessel containing the gas is as empty as a vacuum. Soon, however,
along the track of the beam a beautiful sky-blue colour is observed,
which is due to the liberated particles of sulphur. For a time the blue
grows more intense: it then becomes whitish; and from a whitish blue
it passes to a more or less perfect white. If the action be continued
long enough, we end by filling the tube with a dense cloud of sulphur
particles, which by the application of proper means may be rendered
visible.
Here then our ether waves untie the bond of chemical affinity, and
liberate a body--sulphur--which at ordinary temperatures is a solid,
and which therefore soon becomes an object of the senses. We have
first of all the free atoms of sulphur, which are both invisible and
incompetent to stir the retina sensibly with scattered light. But
these atoms gradually coalesce and form particles, which grow larger
by continual accretion until after a minute or two they appear as
sky-matter. In this condition they are invisible themselves, but
competent to send an amount of wave-motion to the retina sufficient to
produce the firmamental blue. The particles continue, or may be caused
to continue, in this condition for a considerable time, during which no
microscope can cope with them. But they continually grow larger, and
pass by insensible gradations into the state of _cloud_, when they
can no longer elude the armed eye. Thus without solution of continuity
we start with matter in the molecule, and end with matter in the mass,
sky-matter being the middle term of the series of transformations.
Instead of sulphurous acid, we might choose from a dozen other
substances, and produce the same effect with any of them. In the case
of some--probably in the case of all--it is possible to preserve
matter in the skyey condition for fifteen or twenty minutes under
the continual operation of the light. During these fifteen or twenty
minutes the particles are constantly growing larger, without ever
exceeding the size requisite to the production of the celestial blue.
Now when two vessels are placed before you, each containing sky-matter,
it is possible to state with great distinctness which vessel contains
the largest particles. The retina is very sensitive to differences
of light, when, as here, the eye is in comparative darkness, and when
the quantities of wave-motion thrown against the retina are small.
The larger particles declare themselves by the greater whiteness of
their scattered light. Call now to mind the observation, or effort
at observation, made by our President, when he failed to distinguish
the particles of mastic in Brücke’s medium, and when you have done so
follow me. I permitted a beam of light to act upon a certain vapour.
In two minutes the azure appeared, but at the end of fifteen minutes
it had not ceased to be azure. After fifteen minutes, for example,
its colour, and some other phenomena, pronounced it to be a blue of
distinctly smaller particles than those sought for in vain by Mr.
Huxley. These particles, as already stated, must have been less than
¹⁄₁₀₀₀₀₀th of an inch in diameter. And now I want you to submit to
your imagination the following question: Here are particles which have
been growing continually for fifteen minutes, and at the end of that
time are demonstrably smaller than those which defied the microscope
of Mr. Huxley:--_what must have been the size of these particles at
the beginning of their growth?_ What notion can you form of the
magnitude of such particles? The distances of stellar space give us
simply a bewildering sense of vastness without leaving any distinct
impression on the mind, and the magnitudes with which we have here to
do bewilder us equally in the opposite direction. We are dealing with
infinitesimals compared with which the test objects of the microscope
are literally immense.
From their perviousness to stellar light, and other considerations,
Sir John Herschel drew some startling conclusions regarding the
density and weight of comets. You know that these extraordinary and
mysterious bodies sometimes throw out tails 100,000,000 of miles in
length, and 50,000 miles in diameter. The diameter of our earth is
8,000 miles. Both it and the sky, and a good portion of space beyond
the sky, would certainly be included in a sphere 10,000 miles across.
Let us fill this sphere with cometary matter, and make it our unit
of measure. An easy calculation informs us that to produce a comet’s
tail of the size just mentioned about 300,000 such measures would
have to be emptied into space. Now suppose the whole of this stuff
to be swept together, and suitably compressed, what do you suppose
its volume would be? Sir John Herschel would probably tell you that
the whole mass might be carted away at a single effort by one of your
dray-horses. In fact, I do not know that he would require more than
a small fraction of a horse-power to remove the cometary dust. After
this you will hardly regard as monstrous a notion I have sometimes
entertained concerning the quantity of matter in our sky. Suppose a
shell to surround the earth at a height above the surface which would
place it beyond the grosser matter that hangs in the lower regions of
the air--say at the height of the Matterhorn or Mont Blanc. Outside
this shell we have the deep blue firmament. Let the atmospheric space
beyond the shell be swept clean, and let the sky-matter be properly
gathered up. What is its probable amount? I have sometimes thought that
a lady’s portmanteau would contain it all. I have thought that even a
gentleman’s portmanteau--possibly his snuffbox--might take it in. And
whether the actual sky be capable of this amount of condensation or
not, I entertain no doubt that a sky quite as vast as ours, and as good
in appearance, could be formed from a quantity of matter which might be
held in the hollow of the hand.
Small in mass, the vastness in point of number of the particles of
our sky may be inferred from the continuity of its light. It is not
in broken patches, nor at scattered points that the heavenly azure
is revealed. To the observer on the summit of Mont Blanc the blue
is as uniform and coherent as if it formed the surface of the most
close-grained solid. A marble dome would not exhibit a stricter
continuity. And Mr. Glaisher will inform you that if our hypothetical
shell were lifted to twice the height of Mont Blanc above the earth’s
surface, we should still have the azure overhead. Everywhere through
the atmosphere those sky-particles are strewn. They fill the Alpine
valleys, spreading like a delicate gauze in front of the slopes of
pine. They sometimes so swathe the peaks with light as to abolish
their definition. This year I have seen the Weisshorn thus dissolved
in opalescent air. By proper instruments the glare thrown from the
sky-particles against the retina may be quenched, and then the mountain
which it obliterated starts into sudden definition. Its extinction in
front of a dark mountain resembles exactly the withdrawal of a veil. It
is the light then taking possession of the eye, and not the particles
acting as opaque bodies, that interfere with the definition. By day
this light quenches the stars; even by moonlight it is able to exclude
from vision all stars between the fifth and the eleventh magnitude.
It may be likened to a noise, and the stellar radiance to a whisper
drowned by the noise. What is the nature of the particles which shed
light? The celebrated De la Rive ascribes the haze of the Alps in
fine weather to floating organic germs. Now the possible existence
of germs in such profusion has been held up as an absurdity. It has
been affirmed that they would darken the air, and on the assumed
impossibility of their existence in the requisite numbers, without
invasion of the solar light, a powerful argument has been based by
believers in spontaneous generation. Similar arguments have been used
by the opponents of the germ theory of epidemic disease, and both
parties have triumphantly challenged an appeal to the microscope and
the chemist’s balance to decide the question. Such arguments are
absolutely valueless. Without committing myself in the least to De la
Rive’s notion, without offering any objection here to the doctrine of
spontaneous generation, without expressing any adherence to the germ
theory of disease, I would simply draw attention to the fact that in
the atmosphere we have particles which defy both the microscope and the
balance, which do not darken the air, and which exist, nevertheless,
in multitudes sufficient to reduce to insignificance the Israelitish
hyperbole regarding the sands upon the seashore.
The varying judgments of men on these and other questions may perhaps
be, to some extent, accounted for by that doctrine of Relativity which
plays so important a part in philosophy. This doctrine affirms that
the impressions made upon us by any circumstance, or combination of
circumstances, depends upon our previous state. Two travellers upon
the same peak, the one having ascended to it from the plain, the other
having descended to it from a higher elevation, will be differently
affected by the scene around them. To the one nature is expanding, to
the other it is contracting, and feelings are sure to differ which
have two such different antecedent states. In our scientific judgments
the law of relativity may also play an important part. To two men, one
educated in the school of the senses, who has mainly occupied himself
with observation, and the other educated in the school of imagination
as well, and exercised in the conceptions of atoms and molecules to
which we have so frequently referred, a bit of matter, say ¹⁄₅₀₀₀₀th of
an inch in diameter, will present itself differently. The one descends
to it from his molar heights, the other climbs to it from his molecular
lowlands. To the one it appears small, to the other large. So also as
regards the appreciation of the most minute forms of life revealed by
the microscope. To one of these men they naturally appear conterminous
with the ultimate particles of matter, and he readily figures the
molecules from which they directly spring; with him there is but a
step from the atom to the organism. The other discerns numberless
organic gradations between both. Compared with his atoms, the smallest
vibrios and bacteria of the microscopic field are as behemoth and
leviathan. The law of relativity may to some extent explain the
different attitudes of these two men with regard to the question of
spontaneous generation. An amount of evidence which satisfies the
one entirely fails to satisfy the other; and while to the one the
last bold defence and startling expansion of the doctrine will appear
perfectly conclusive, to the other it will present itself as imposing a
profitless labour of demolition on subsequent investigators.[4]
I trust, Mr. President, that you--whom untoward circumstances have
made a biologist, but who still keep alive your sympathy with that
class of enquiries which nature intended you to pursue and adorn--will
excuse me to your brethren if I say that some of them seem to form an
inadequate estimate of the distance which separates the microscopic
from the molecular limit, and that, as a consequence, they sometimes
employ a phraseology which is calculated to mislead. When, for example,
the contents of a cell are described as perfectly homogeneous, as
absolutely structureless, because the microscope fails to distinguish
any structure, then I think the microscope begins to play a mischievous
part. A little consideration will make it plain to all of you that the
microscope can have no voice in the real question of germ structure.
Distilled water is more perfectly homogeneous than the contents of any
possible organic germ. What causes the liquid to cease contracting at
39° Fahr., and to grow bigger until it freezes? It is a structural
process of which the microscope can take no note, nor is it likely to
do so by any conceivable extension of its powers. Place this distilled
water in the field of an electro-magnet, and bring a microscope to
bear upon it. Will any change be observed when the magnet is excited?
Absolutely none; and still profound and complex changes have occurred.
First of all, the particles of water are rendered diamagnetically
polar; and secondly, in virtue of the structure impressed upon it
by the magnetic strain of its molecules, the liquid twists a ray of
light in a fashion perfectly determinate both as to quantity and
direction. It would be immensely interesting to both you and me if one
whom I hoped to see here present,[5] who has brought his brilliant
imagination to bear upon this subject, could make us see as he sees the
entangled molecular processes involved in the rotation of the plane
of polarisation by magnetic force. While dealing with this question,
he lived in a world of matter and of motion to which the microscope
has no passport, and in which it can offer no aid. The cases in which
similar conditions hold are simply numberless. Have the diamond, the
amethyst, and the countless other crystals formed in the laboratories
of nature and of man no structure? Assuredly they have; but what can
the microscope make of it? Nothing. It cannot be too distinctly borne
in mind that between the microscope limit and the true molecular limit
there is room for infinite permutations and combinations. It is in
this region that the poles of the atoms are arranged, that tendency
is given to their powers, so that when these poles and powers have
free action and proper stimulus in a suitable environment, they
determine first the germ and afterwards the complete organism. This
first marshalling of the atoms on which all subsequent action depends
baffles a keener power than that of the microscope. Through pure
excess of complexity, and long before observation can have any voice
in the matter, the most highly trained intellect, the most refined and
disciplined imagination, retires in bewilderment from the contemplation
of the problem. We are struck dumb by an astonishment which no
microscope can relieve, doubting not only the power of our instrument,
but even whether we ourselves possess the intellectual elements which
will ever enable us to grapple with the ultimate structural energies of
nature.
But the speculative faculty, of which imagination forms so large a
part, will nevertheless wander into regions where the hope of certainty
would seem to be entirely shut out. We think that though the detailed
analysis may be, and may ever remain, beyond us, general notions may
be attainable. At all events, it is plain that beyond the present
outposts of microscopic enquiry lies an immense field for the exercise
of the speculative power. It is only, however, the privileged spirits
who know how to use their liberty without abusing it, who are able to
surround imagination by the firm frontiers of reason, that are likely
to work with any profit here. But freedom to them is of such paramount
importance that, for the sake of securing it, a good deal of wildness
on the part of weaker brethren may be overlooked. In more senses
than one Mr. Darwin has drawn heavily upon the scientific tolerance
of his age. He has drawn heavily upon _time_ in his development
of species, and he has drawn adventurously upon _matter_ in
his theory of pangenesis. According to this theory, a germ already
microscopic is a world of minor germs. Not only is the organism as a
whole wrapped up in the germ, but every organ of the organism has there
its special seed. This, I say, is an adventurous draft on the power of
matter to divide itself and distribute its forces. But, unless we are
perfectly sure that he is overstepping the bounds of reason, that he
is unwittingly sinning against observed fact or demonstrated law--for
a mind like that of Darwin can never sin wittingly against either fact
or law--we ought, I think, to be cautious in limiting his intellectual
horizon. If there be the least doubt in the matter, it ought to be
given in favour of the freedom of such a mind. To it a vast possibility
is in itself a dynamic power, though the possibility may never be drawn
upon. It gives me pleasure to think that the facts and reasonings of
this discourse tend rather towards the justification of Mr. Darwin than
towards his condemnation, that they tend rather to augment than to
diminish the cubic space demanded by this soaring speculator; for they
seem to show the perfect competence of matter and force, as regards
divisibility and distribution, to bear the heaviest strain that he has
hitherto imposed upon them.
In the case of Mr. Darwin, observation, imagination, and reason
combined have run back with wonderful sagacity and success over a
certain length of the line of biological succession. Guided by analogy,
in his ‘Origin of Species,’ he placed at the root of life a primordial
germ, from which he conceived the amazing richness and variety of
the life that now is upon the earth’s surface might be deduced. If
this were true, it would not be final. The human imagination would
infallibly look behind the germ, and enquire into the history of its
genesis. Certainty is here hopeless, but the materials for an opinion
may be attainable. In this dim twilight of conjecture the enquirer
welcomes every gleam, and seeks to augment his light by indirect
incidences. He studies the methods of nature in the ages and the
worlds within his reach, in order to shape the course of speculation
in the antecedent ages and worlds. And though the certainty possessed
by experimental enquiry is here shut out, the imagination is not left
entirely without guidance. From the examination of the solar system,
Kant and Laplace came to the conclusion that its various bodies once
formed parts of the same undislocated mass; that matter in a nebulous
form preceded matter in a dense form; that as the ages rolled away,
heat was wasted, condensation followed, planets were detached,
and that finally the chief portion of the fiery cloud reached, by
self-compression, the magnitude and density of our sun. The earth
itself offers evidence of a fiery origin; and in our day the hypothesis
of Kant and Laplace receives the independent countenance of spectrum
analysis, which proves the same substances to be common to the earth
and sun. Accepting some such view of the construction of our system as
probable, a desire immediately arises to connect the present life of
our planet with the past. We wish to know something of our remotest
ancestry. On its first detachment from the central mass, life, as
we understand it, could hardly have been present on the earth. How
then did it come there? The thing to be encouraged here is a reverent
freedom--a freedom preceded by the hard discipline which checks
licentiousness in speculation--while the thing to be repressed, both in
science and out of it, is dogmatism. And here I am in the hands of the
meeting--willing to end, but ready to go on. I have no right to intrude
upon you, unasked, the unformed notions which are floating like clouds,
or gathering to more solid consistency in the modern speculative
scientific mind. But if you wish me to speak plainly, honestly, and
undisputatiously, I am willing to do so. On the present occasion--
You are ordained to call, and I to come.
Two views, then, offer themselves to us. Life was present potentially
in matter when in the nebulous form, and was unfolded from it by the
way of natural development, or it is a principle inserted into matter
at a later date. With regard to the question of time, the views of
men have changed remarkably in our day and generation; and I must
say as regards courage also, and a manful willingness to engage in
open contest, with fair weapons, a great change has also occurred.
The clergy of England--at all events the clergy of London--have nerve
enough to listen to the strongest views which any one amongst us would
care to utter; and they invite, if they do not challenge, men of the
most decided opinions to state and stand by those opinions in open
court. No theory upsets them. Let the most destructive hypothesis be
stated only in the language current among gentlemen, and they look it
in the face. They forego alike the thunders of heaven and the terrors
of the other place, smiting the theory, if they do not like it, with
honest secular strength. In fact, the greatest cowards of the present
day are not to be found among the clergy, but within the pale of
science itself.
Two or three years ago in an ancient London College--a clerical
institution--I heard a very remarkable lecture by a very remarkable
man. Three or four hundred clergymen were present at the lecture. The
orator began with the civilisation of Egypt in the time of Joseph;
pointing out that the very perfect organisation of the kingdom, and the
possession of chariots, in one of which Joseph rode, indicated a long
antecedent period of civilisation. He then passed on to the mud of the
Nile, its rate of augmentation, its present thickness, and the remains
of human handywork found therein; thence to the rocks which bound the
Nile valley, and which teem with organic remains. Thus in his own clear
and admirable way he caused the idea of the world’s age to expand
itself indefinitely before the mind of his audience, and he contrasted
this with the age usually assigned to the world. During his discourse
he seemed to be swimming against a stream; he manifestly thought that
he was opposing a general conviction. He expected resistance; so did
I. But it was all a mistake: there was no adverse current, no opposing
conviction, no resistance, merely here and there a half-humorous, but
unsuccessful attempt to entangle him in his talk. The meeting agreed
with all that had been said regarding the antiquity of the earth
and of its life. They had, indeed, known it all long ago, and they
good-humouredly rallied the lecturer for coming amongst them with so
stale a story. It was quite plain that this large body of clergymen,
who were, I should say, the finest samples of their class, had entirely
given up the ancient landmarks, and transported the conception of
life’s origin to an indefinitely distant past.
This leads us to the gist of our present enquiry, which is this:--Does
life belong to what we call matter, or is it an independent principle
inserted into matter at some suitable epoch--say when the physical
conditions became such as to permit of the development of life? Let us
put the question with all the reverence due to a faith and culture in
which we all were cradled--a faith and culture, moreover, which are the
undeniable historic antecedents of our present enlightenment. I say,
let us put the question reverently, but let us also put it clearly and
definitely. There are the strongest grounds for believing that during
a certain period of its history the earth was not, nor was it fit to
be, the theatre of life. Whether this was ever a nebulous period, or
merely a molten period, does not much matter; and if we revert to
the nebulous condition, it is because the probabilities are really
on its side. Our question is this:--Did creative energy pause until
the nebulous matter had condensed, until the earth had been detached,
until the solar fire had so far withdrawn from the earth’s vicinity
as to permit a crust to gather round the planet? Did it wait until
the air was isolated, until the seas were formed, until evaporation,
condensation, and the descent of rain had begun, until the eroding
forces of the atmosphere had weathered and decomposed the molten rocks
so as to form soils, until the sun’s rays had become so tempered by
distance and by waste as to be chemically fit for the decompositions
necessary to vegetable life? Having waited through those Æons until the
proper conditions had set in, did it send the fiat forth, ‘Let Life
be!’? These questions define a hypothesis not without its difficulties,
but the dignity of which was demonstrated by the nobleness of the men
whom it sustained.
Modern scientific thought is called upon to decide between this
hypothesis and another: and public thought generally will afterwards be
called upon to do the same. You may, however, rest secure in the belief
that the hypothesis just sketched can never be stormed, and that it is
sure, if it yield at all, to yield to a prolonged siege. To gain new
territory modern argument requires more time than modern arms, though
both of them move with greater rapidity than of yore. But however
the convictions of individuals here and there may be influenced, the
process must be slow and secular which commends the rival hypothesis
of Natural Evolution to the public mind. For what are the core and
essence of this hypothesis? Strip it naked and you stand face to face
with the notion that not alone the more ignoble forms of animalcular
or animal life, not alone the nobler forms of the horse and lion, not
alone the exquisite and wonderful mechanism of the human body, but
that the human mind itself--emotion, intellect, will, and all their
phenomena--were once latent in a fiery cloud. Surely the mere statement
of such a notion is more than a refutation. But the hypothesis would
probably go even further than this. Many who hold it would probably
assent to the position that at the present moment all our philosophy,
all our poetry, all our science, and all our art--Plato, Shakspeare,
Newton, and Raphael--are potential in the fires of the sun. We long to
learn something of our origin. If the Evolution hypothesis be correct,
even this unsatisfied yearning must have come to us across the ages
which separate the unconscious primeval mist from the consciousness
of to-day. I do not think that any holder of the Evolution hypothesis
would say that I overstate it or overstrain it in any way. I merely
strip it of all vagueness, and bring before you unclothed and
unvarnished the notions by which it must stand or fall.
Surely these notions represent an absurdity too monstrous to be
entertained by any sane mind. Let us, however, give them fair play. Let
us steady ourselves in front of the hypothesis, and, dismissing all
terror and excitement from our minds, let us look firmly into it with
the hard sharp eye of intellect alone. Why are these notions absurd,
and why should sanity reject them? The law of Relativity, of which we
have previously spoken, may find its application here. These Evolution
notions are absurd, monstrous, and fit only for the intellectual
gibbet in relation to the ideas concerning matter which were drilled
into us when young. Spirit and matter have ever been presented to us
in the rudest contrast, the one as all-noble, the other as all-vile.
But is this correct? Does it represent what our mightiest spiritual
teacher would call the Eternal Fact of the Universe? Upon the answer to
this question all depends. Supposing, instead of having the foregoing
antithesis of spirit and matter presented to our youthful minds, we had
been taught to regard them as equally worthy and equally wonderful; to
consider them in fact as two opposite faces of the self-same mystery.
Supposing that in youth we had been impregnated with the notion of
the poet Goethe, instead of the notion of the poet Young, looking
at matter, not as brute matter, but as ‘the living garment of God;’
do you not think that under these altered circumstances the law of
Relativity might have had an outcome different from its present one?
Is it not probable that our repugnance to the idea of primeval union
between spirit and matter might be considerably abated? Without this
total revolution of the notions now prevalent, the Evolution hypothesis
must stand condemned; but in many profoundly thoughtful minds such
a revolution has already taken place. They degrade neither member
of the mysterious duality referred to; but they exalt one of them
from its abasement, and repeal the divorce hitherto existing between
both. In substance, if not in words, their position as regards the
relation of spirit and matter is: ‘What God hath joined together let
not man put asunder.’ And with regard to the ages of forgetfulness
which lie between the unconscious life of the nebula and the conscious
life of the earth, it is, they would urge, but an extension of that
forgetfulness which preceded the birth of us all.
I have thus led you to the outer rim of speculative science, for
beyond the nebulæ scientific thought has never ventured hitherto, and
have tried to state that which I considered ought, in fairness, to be
outspoken. I do not think this Evolution hypothesis is to be flouted
away contemptuously; I do not think it is to be denounced as wicked.
It is to be brought before the bar of disciplined reason, and there
justified or condemned. Let us hearken to those who wisely support
it, and to those who wisely oppose it; and let us tolerate those, and
they are many, who foolishly try to do either of these things.[6] The
only thing out of place in the discussion is dogmatism on either side.
Fear not the Evolution hypothesis. Steady yourselves in its presence
upon that faith in the ultimate triumph of truth which was expressed
by old Gamaliel when he said:--‘If it be of God, ye cannot overthrow
it; if it be of man, it will come to nought.’ Under the fierce light
of scientific enquiry, this hypothesis is sure to be dissipated if it
possess not a core of truth. Trust me, its existence as a hypothesis
in the mind is quite compatible with the simultaneous existence of all
those virtues to which the term Christian has been applied. It does
not solve--it does not profess to solve--the ultimate mystery of this
universe. It leaves in fact that mystery untouched. For granting the
nebula and its potential life, the question, whence came they? would
still remain to baffle and bewilder us. At bottom, the hypothesis does
nothing more than ‘transport the conception of life’s origin to an
indefinitely distant past.’
Those who hold the doctrine of Evolution are by no means ignorant of
the uncertainty of their data, and they yield no more to it than a
provisional assent. They regard the nebular hypothesis as probable,
and in the utter absence of any evidence to prove the act illegal,
they extend the method of nature from the present into the past. Here
the observed uniformity of nature is their only guide. Within the long
range of physical enquiry, they have never discerned in nature the
insertion of caprice. Throughout this range the laws of physical and
intellectual continuity have run side by side. Having thus determined
the elements of their curve in a world of observation and experiment,
they prolong that curve into an antecedent world, and accept as
probable the unbroken sequence of development from the nebula to the
present time. You never hear the really philosophical defenders of the
doctrine of Uniformity speaking of _impossibilities_ in nature.
They never say, what they are constantly charged with saying, that
it is impossible for the Builder of the universe to alter His work.
Their business is not with the possible, but the actual--not with a
world which _might_ be, but with a world that _is_. This
they explore with a courage not unmixed with reverence, and according
to methods which, like the quality of a tree, are tested by their
fruits. They have but one desire--to know the truth. They have but one
fear--to believe a lie. And if they know the strength of science, and
rely upon it with unswerving trust, they also know the limits beyond
which science ceases to be strong. They best know that questions
offer themselves to thought which science, as now prosecuted, has not
even the tendency to solve. They keep such questions open, and will
not tolerate any unlawful limitation of the horizon of their souls.
They have as little fellowship with the atheist who says there is no
God, as with the theist who professes to know the mind of God. ‘Two
things,’ said Immanuel Kant, ‘fill me with awe: the starry heavens
and the sense of moral responsibility in man.’ And in his hours of
health and strength and sanity, when the stroke of action has ceased
and the pause of reflection has set in, the scientific investigator
finds himself overshadowed by the same awe. Breaking contact with the
hampering details of earth, it associates him with a power which gives
fulness and tone to his existence, but which he can neither analyse nor
comprehend.
SCIENTIFIC LIMIT OF THE IMAGINATION.[7]
THE CELEBRATED FICHTE, in his lectures on the ‘Vocation of the
Scholar,’ insisted on a culture for the scholar which should not
be one-sided, but all-sided. His intellectual nature was to expand
spherically and not in a single direction. In one direction, however,
Fichte required that the scholar should apply himself directly to
nature, become a creator of knowledge, and thus repay by original
labours of his own the immense debt he owed to the labours of others.
It was these which enabled him to supplement the knowledge derived
from his own researches, so as to render his culture rounded and not
one-sided.
As regards science Fichte’s idea is to some extent illustrated by
the constitution and the labours of the British Association. We have
here a body of men engaged in the pursuit of Natural Knowledge, but
variously engaged. While sympathizing with each of its departments,
and supplementing his culture by knowledge drawn from all of them,
each student amongst us selects one subject for the exercise of his
own original faculty--one line along which he may carry the light of
his private intelligence a little way into the darkness by which all
knowledge is surrounded. Thus, the geologist deals with the rocks; the
biologist with the conditions and phenomena of life; the astronomer
with stellar masses and motions; the mathematician with the relations
of space and number; the chemist pursues his atoms, while the physical
investigator has his own large field in optical, thermal, electrical,
acoustical, and other phenomena. The British Association then, as
a whole, faces physical nature on all sides and pushes knowledge
centrifugally outwards, the sum of its labours constituting what Fichte
might call the _sphere_ of natural knowledge. In the meetings of
the Association it is found necessary to resolve this sphere into its
component parts, which take concrete form under the respective letters
of our Sections.
This is the Mathematical and Physical Section. Mathematics and physics
have been long accustomed to coalesce. For, no matter how subtle a
natural phenomenon may be, whether we observe it in the region of
sense, or follow it into that of imagination, it is in the long run
reducible to mechanical laws. But the mechanical data once guessed or
given, mathematics become all powerful as an instrument of deduction.
The command of geometry over the relations of space, the far-reaching
power which organised symbolic reasoning confers, are potent both
as means of physical discovery, and of reaping the entire fruits of
discovery. Indeed, without mathematics, expressed or implied, our
knowledge of physical science would be friable in the extreme.
Side by side with the mathematical method we have the method of
experiment. Here, from a starting-point furnished by his own researches
or those of others, the investigator proceeds by combining intuition
and verification. He ponders the knowledge he possesses and tries to
push it further, he guesses and checks his guess, he conjectures and
confirms or explodes his conjecture. These guesses and conjectures
are by no means leaps in the dark; for knowledge once gained casts a
faint light beyond its own immediate boundaries. There is no discovery
so limited as not to illuminate something beyond itself. The force of
intellectual penetration into this penumbral region which surrounds
actual knowledge is not, as some seem to think, dependent upon method,
but upon the genius of the investigator. There is, however, no genius
so gifted as not to need control and verification. The profoundest
minds know best that Nature’s ways are not at all times their ways, and
that the brightest flashes in the world of thought are incomplete until
they have been proved to have their counterparts in the world of fact.
Thus the vocation of the true experimentalist may be defined as the
continued exercise of spiritual insight, and its incessant correction
and realization. His experiments constitute a body, of which his
purified intuitions are, as it were, the soul.
Partly through mathematical and partly through experimental research,
physical science has of late years assumed a momentous position in the
world. Both in a material and in an intellectual point of view it has
produced, and it is destined to produce, immense changes,--vast social
ameliorations, and vast alterations in the popular conception of the
origin, rule, and governance of natural things. By science, in the
physical world, miracles are wrought, while philosophy is forsaking
its ancient metaphysical channels and pursuing others which have been
opened or indicated by scientific research. This must become more and
more the case as philosophic writers become more deeply imbued with the
methods of science, better acquainted with the facts which scientific
men have won, and with the great theories which they have elaborated.
If you look at the face of a watch, you see the hour and minute-hands,
and possibly also a second-hand, moving over the graduated dial. Why do
these hands move? and why are their relative motions such as they are
observed to be? These questions cannot be answered without opening the
watch, mastering its various parts, and ascertaining their relationship
to each other. When this is done, we find that the observed motion of
the hands follows of necessity from the inner mechanism of the watch,
when acted upon by the force invested in the spring.
The motion of the hands may be called a phenomenon of art, but the case
is similar with the phenomena of nature. These also have their inner
mechanism, and their store of force to set that mechanism going. The
ultimate problem of physical science is to reveal this mechanism, to
discern this store, and to show that from the combined action of both
the phenomena of which they constitute the basis must of necessity flow.
I thought that an attempt to give you even a brief and sketchy
illustration of the manner in which scientific thinkers regard this
problem would not be uninteresting to you on the present occasion;
more especially as it will give me occasion to say a word or two on
the tendencies and limits of modern science; to point out the region
which men of science claim as their own, and where it is mere waste
of time to oppose their advance, and also to define, if possible, the
bourne between this and that other region to which the questionings and
yearnings of the scientific intellect are directed in vain.
But here your tolerance will be needed. It was the American Emerson, I
think, who said that it is hardly possible to state any truth strongly
without apparent injustice to some other truth. Truth is often of a
dual character, taking the form of a magnet with two poles; and many
of the differences which agitate the thinking part of mankind are to
be traced to the exclusiveness with which partisan reasoners dwell
upon one half of the duality in forgetfulness of the other half. The
proper course appears to be to state both halves strongly, and allow
each its fair share in the formation of the resultant conviction. But
this waiting for the statement of the two sides of a question implies
patience. It implies a resolution to suppress indignation if the
statement of the one half should clash with our convictions, and to
repress equally undue elation if the half-statement should happen to
chime in with our views. It implies a determination to wait calmly for
the statement of the whole, before we pronounce judgment in the form of
either acquiescence or dissent.
This premised, and, I trust, accepted, let us enter upon our task.
There have been writers who affirmed that the pyramids of Egypt were
the productions of nature; and in his early youth Alexander von
Humboldt wrote a learned essay with the express object of refuting
this notion. We now regard the pyramids as the work of men’s hands,
aided probably by machinery of which no record remains. We picture to
ourselves the swarming workers toiling at those vast erections, lifting
the inert stones, and, guided by the volition, the skill, and possibly
at times by the whip of the architect, placing them in their proper
positions. The blocks in this case were moved and posited by a power
external to themselves, and the final form of the pyramid expressed the
thought of its human builder.
Let us pass from this illustration of constructive power to another of
a different kind. When a solution of common salt is slowly evaporated,
the water which holds the salt in solution disappears, but the salt
itself remains behind. At a certain stage of concentration the salt
can no longer retain the liquid form; its particles, or molecules,
as they are called, begin to deposit themselves as minute solids,
so minute, indeed, as to defy all microscopic power. As evaporation
continues solidification goes on, and we finally obtain, through the
clustering together of innumerable molecules, a finite crystalline mass
of a definite form. What is this form? It sometimes seems a mimicry
of the architecture of Egypt. We have little pyramids built by the
salt, terrace above terrace from base to apex, forming a series of
steps resembling those up which the Egyptian traveller is dragged by
his guides. The human mind is as little disposed to look unquestioning
at these pyramidal salt-crystals as to look at the pyramids of Egypt
without inquiring whence they came. How, then, are those salt-pyramids
built up?
Guided by analogy, you may, if you like, suppose that, swarming
among the constituent molecules of the salt, there is an invisible
population, guided and coerced by some invisible master, and placing
the atomic blocks in their positions. This, however, is not the
scientific idea, nor do I think your good sense will accept it as a
likely one. The scientific idea is that the molecules act upon each
other without the intervention of slave labour; that they attract each
other and repel each other at certain definite points, or poles, and in
certain definite directions; and that the pyramidal form is the result
of this play of attraction and repulsion. While, then, the blocks of
Egypt were laid down by a power external to themselves, these molecular
blocks of salt are self-posited, being fixed in their places by the
forces with which they act upon each other.
I take common salt as an illustration because it is so familiar to
us all; but any other crystalline substance would answer my purpose
equally well. Everywhere, in fact, throughout inorganic nature, we have
this formative power, as Fichte would call it--this structural energy
ready to come into play, and build the ultimate particles of matter
into definite shapes. The ice of our winters and of our polar regions
is its handywork, and so equally are the quartz, felspar, and mica of
our rocks. Our chalk-beds are for the most part composed of minute
shells, which are also the product of structural energy; but behind the
shell, as a whole, lies a more remote and subtle formative act. These
shells are built up of little crystals of calc-spar, and to form these
crystals the structural force had to deal with the intangible molecules
of carbonate of lime. This tendency on the part of matter to organize
itself, to grow into shape, to assume definite forms in obedience to
the definite action of force, is, as I have said, all-pervading. It is
in the ground on which you tread, in the water you drink, in the air
you breathe. Incipient life, as it were, manifests itself throughout
the whole of what we call inorganic nature.
The forms of the minerals resulting from this play of polar forces are
various, and exhibit different degrees of complexity. Men of science
avail themselves of all possible means of exploring their molecular
architecture. For this purpose they employ in turn as agents of
exploration, light, heat, magnetism, electricity, and sound. Polarized
light is especially useful and powerful here. A beam of such light,
when sent in among the molecules of a crystal, is acted on by them, and
from this action we infer with more or less of clearness the manner
in which the molecules are arranged. That differences, for example,
exist between the inner structure of rock salt and crystallized sugar
or sugar-candy, is thus strikingly revealed. These differences may be
made to display themselves in chromatic phenomena of great splendour,
the play of molecular force being so regulated as to remove some of
the coloured constituents of white light, and to leave others with
increased intensity behind.
And now let us pass from what we are accustomed to regard as a dead
mineral to a living grain of corn. When it is examined by polarized
light, chromatic phenomena similar to those noticed in crystals are
observed. And why? Because the architecture of the grain resembles the
architecture of the crystal. In the grain also the molecules are set in
definite positions, and in accordance with their arrangement they act
upon the light. But what has built together the molecules of the corn?
I have already said regarding crystalline architecture that you may, if
you please, consider the atoms and molecules to be placed in position
by a power external to themselves. The same hypothesis is open to you
now. But if in the case of crystals you have rejected this notion of
an external architect, I think you are bound to reject it now, and to
conclude that the molecules of the corn are self-posited by the forces
with which they act upon each other. It would be poor philosophy to
invoke an external agent in the one case and to reject it in the other.
Instead of cutting our grain of corn into slices and subjecting it to
the action of polarized light, let us place it in the earth and subject
it to a certain degree of warmth. In other words, let the molecules,
both of the corn and of the surrounding earth, be kept in that state
of agitation which we call warmth. Under these circumstances, the
grain and the substances which surround it interact, and a definite
molecular architecture is the result. A bud is formed; this bud reaches
the surface, where it is exposed to the sun’s rays, which are also to
be regarded as a kind of vibratory motion. And as the motion of common
heat with which the grain and the substances surrounding it were first
endowed, enabled the grain and these substances to exercise their
attractions and repulsions, and thus to coalesce in definite forms,
so the specific motion of the sun’s rays now enables the green bud to
feed upon the carbonic acid and the aqueous vapour of the air. The bud
appropriates those constituents of both for which it has an elective
attraction, and permits the other constituent to resume its place in
the air. Thus the architecture is carried on. Forces are active at the
root, forces are active in the blade, the matter of the earth and the
matter of the atmosphere are drawn towards both, and the plant augments
in size. We have in succession, the bud, the stalk, the ear, the full
corn in the ear; the cycle of molecular action being completed by the
production of grains similar to that with which the process began.
Now there is nothing in this process which necessarily eludes the
conceptive or imagining power of the purely human mind. An intellect
the same in kind as our own would, if only sufficiently expanded, be
able to follow the whole process from beginning to end. It would see
every molecule placed in its position by the specific attractions and
repulsions exerted between it and other molecules, the whole process
and its consummation being an instance of the play of molecular force.
Given the grain and its environment, the purely human intellect might,
if sufficiently expanded, trace out _à priori_ every step of
the process of growth, and by the application of purely mechanical
principles demonstrate that the cycle must end, as it is seen to end,
in the reproduction of forms like that with which it began. A similar
necessity rules here to that which rules the planets in their circuits
round the sun.
You will notice that I am stating my truth strongly, as at the
beginning we agreed it should be stated. But I must go still further,
and affirm that in the eye of science _the animal body_ is just
as much the product of molecular force as the stalk and ear of corn,
or as the crystal of salt or sugar. Many of the parts of the body are
obviously mechanical. Take the human heart, for example, with its
system of valves, or take the exquisite mechanism of the eye or hand.
Animal heat, moreover, is the same in kind as the heat of a fire,
being produced by the same chemical process. Animal motion, too, is
as directly derived from the food of the animal, as the motion of
Trevethyck’s walking-engine from the fuel in its furnace. As regards
matter, the animal body creates nothing; as regards force, it creates
nothing. Which of you by taking thought can add one cubit to his
stature? All that has been said, then, regarding the plant may be
restated with regard to the animal. Every particle that enters into
the composition of a muscle, a nerve, or a bone, has been placed in
its position by molecular force. And unless the existence of law in
these matters be denied, and the element of caprice introduced, we
must conclude that, given the relation of any molecule of the body
to its environment, its position in the body might be determined
mathematically. Our difficulty is not with the _quality_ of the
problem, but with its _complexity_; and this difficulty might be
met by the simple expansion of the faculties which we now possess.
Given this expansion, with the necessary molecular data, and the chick
might be deduced as rigorously and as logically from the egg as the
existence of Neptune was deduced from the disturbances of Uranus, or as
conical refraction was deduced from the undulatory theory of light.
You see I am not mincing matters, but avowing nakedly what many
scientific thinkers more or less distinctly believe. The formation of
a crystal, a plant, or an animal, is in their eyes a purely mechanical
problem, which differs from the problems of ordinary mechanics in the
smallness of the masses and the complexity of the processes involved.
Here you have one half of our dual truth; let us now glance at the
other half. Associated with this wonderful mechanism of the animal
body we have phenomena no less certain than those of physics, but
between which and the mechanism we discern no necessary connexion. A
man, for example, can say _I feel, I think, I love_; but how does
_consciousness_ infuse itself into the problem? The human brain
is said to be the organ of thought and feeling; when we are hurt the
brain feels it, when we ponder it is the brain that thinks, when our
passions or affections are excited it is through the instrumentality of
the brain. Let us endeavour to be a little more precise here. I hardly
imagine there exists a profound scientific thinker, who has reflected
upon the subject, unwilling to admit the extreme probability of the
hypothesis, that for every fact of consciousness, whether in the domain
of sense, of thought, or of emotion, a certain definite molecular
condition is set up in the brain; who does not hold this relation of
physics to consciousness to be invariable, so that, given the state
of the brain, the corresponding thought or feeling might be inferred;
or given the thought or feeling, the corresponding state of the brain
might be inferred.
But how inferred? It is at bottom not a case of logical inference
at all, but of empirical association. You may reply that many of
the inferences of science are of this character; the inference, for
example, that an electric current of a given direction will deflect a
magnetic needle in a definite way; but the cases differ in this, that
the passage from the current to the needle, if not demonstrable, is
thinkable, and that we entertain no doubt as to the final mechanical
solution of the problem. But the passage from the physics of the
brain to the corresponding facts of consciousness is unthinkable.
Granted that a definite thought, and a definite molecular action in
the brain occur simultaneously; we do not possess the intellectual
organ, nor apparently any rudiment of the organ, which would enable us
to pass, by a process of reasoning, from the one to the other. They
appear together, but we do not know why. Were our minds and senses so
expanded, strengthened, and illuminated as to enable us to see and
feel the very molecules of the brain; were we capable of following all
their motions, all their groupings, all their electric discharges, if
such there be; and were we intimately acquainted with the corresponding
states of thought and feeling, we should be as far as ever from the
solution of the problem. ‘How are these physical processes connected
with the facts of consciousness?’ The chasm between the two classes
of phenomena would still remain intellectually impassable. Let the
consciousness of _love_, for example, be associated with a
right-handed spiral motion of the molecules of the brain, and the
consciousness of _hate_ with a left-handed spiral motion. We
should then know when we love that the motion is in one direction, and
when we hate that the motion is in the other; but the ‘WHY?’
would remain as unanswerable as before.
In affirming that the growth of the body is mechanical, and that
thought, as exercised by us, has its correlative in the physics of
the brain, I think the position of the ‘Materialist’ is stated, as
far as that position is a tenable one. I think the materialist will
be able finally to maintain this position against all attacks; but
I do not think, in the present condition of the human mind, that he
can pass beyond this position. I do not think he is entitled to say
that his molecular groupings and his molecular motions _explain_
everything. In reality they explain nothing. The utmost he can affirm
is the association of two classes of phenomena, of whose real bond
of union he is in absolute ignorance. The problem of the connexion
of body and soul is as insoluble in its modern form as it was in the
prescientific ages. Phosphorus is known to enter into the composition
of the human brain, and a trenchant German writer has exclaimed, ‘Ohne
Phosphor, kein Gedanke.’ That may or may not be the case; but even
if we knew it to be the case, the knowledge would not lighten our
darkness. On both sides of the zone here assigned to the materialist he
is equally helpless. If you ask him whence is this ‘Matter’ of which
we have been discoursing, who or what divided it into molecules, who
or what impressed upon them this necessity of running into organic
forms, he has no answer. Science is mute in reply to these questions.
But if the materialist is confounded and science rendered dumb, who
else is prepared with a solution? To whom has this arm of the Lord
been revealed? Let us lower our heads and acknowledge our ignorance,
priest and philosopher, one and all. Perhaps the mystery may resolve
itself into knowledge at some future day. The process of things upon
this earth has been one of amelioration. It is a long way from the
Iguanodon and his contemporaries to the President and Members of the
British Association. And whether we regard the improvement from the
scientific or from the theological point of view, as the result of
progressive development, or as the result of successive exhibitions of
creative energy, neither view entitles us to assume that man’s present
faculties end the series,--that the process of amelioration stops at
him. A time may therefore come when this ultra-scientific region by
which we are now enfolded may offer itself to terrestrial, if not to
human investigation. Two-thirds of the rays emitted by the sun fail to
arouse in the eye the sense of vision. The rays exist, but the visual
organ requisite for their translation into light does not exist. And
so from this region of darkness and mystery which surrounds us, rays
may now be darting which require but the development of the proper
intellectual organs to translate them into knowledge as far surpassing
ours as ours surpasses that of the wallowing reptiles which once held
possession of this planet. Meanwhile the mystery is not without its
uses. It certainly may be made a power in the human soul; but it is
a power which has feeling, not knowledge, for its base. It may be,
and will be, and we hope is turned to account, both in steadying and
strengthening the intellect, and in rescuing man from that littleness
to which, in the struggle for existence, or for precedence in the
world, he is continually prone.
EARLIER THOUGHTS.[8]
A WORK recently published by Mr. Murray contains a sketch of the
grounds on which the most advanced scientific thinkers of the present
day base their convictions as to the physical character of Light and
Heat. The fundamental idea there developed is, that the phenomena of
light and heat, like those of sound, are essentially _mechanical_.
Precisely the same reasoning applies to the vibrating ether which
produces the one as to the vibrating air which produces the other, and
both are dealt with substantially as we should deal with the waves of
a liquid or the swing of a pendulum. Reflection on this subject has
suggested the thought that the considerations brought forward in the
sketch referred to may apply themselves to certain phenomena which are
usually considered to lie outside the pale of physics, and thus may
indicate new relationships between man regarded as a being of intellect
and emotion, and the wondrous material system in the midst of which he
dwells.
All our intercourse with the external world consists exclusively in an
interchange of motion. From a vibrating, sonorous body, for example,
pulses are sent to the ear and stir the auditory nerve to motion. From
a luminous body pulses are sent to the eye, and stir the optic nerve to
motion. Other pulses of different periods strike upon other nerves,
and produce the sensation of heat; but, in all cases, whether it be
light, or sound, or ordinary feeling, the excitement of the nerves,
regarded more strictly, is the excitement of motion. And if the motion
be induced by internal causes instead of external, is it not fair
to infer that the effect on consciousness will be the same? Let any
nerve, for example, be thrown by morbid action into the precise state
of motion which would be communicated to it by the pulses of a heated
body, surely that nerve will declare itself hot--the mind will accept
the subjective intimation exactly as if it were objective. The retina,
as is well known, may be excited by purely mechanical means. A blow
on the eye will cause a luminous flash, and the mere pressure of the
finger on the external ball will produce a star of light, which Newton
compared to the circles on a peacock’s tail. Disease makes people see
visions and dream dreams; but, in all such cases, could we examine the
organs implicated, we should, on philosophical grounds, expect to find
them in that precise molecular condition which the real objects, if
present, would superinduce.
The colour of light is determined by the frequency of the ethereal
vibrations, as the pitch of sound is determined by the frequency of
the aërial ones. The red or purple, for example, of a British maiden’s
cheek and lips, the blue, violet, or brown of her eyes, have their
strict physical equivalents in the lengths of the waves which issue
from them; and these waves are not only as truly mechanical as the
waves of the sea, but they are capable of having their mechanical
value expressed in numbers. In the work already referred to, a chapter
is devoted to the relation which subsists between light and heat and
mere mechanical work. In virtue of this relation we can tell the
precise amount of work which a given amount of sunshine can perform.
Now, the hue of the cheek is caused by the extinction of certain of
the solar rays by the colouring matter of the cheek, the residual
colour being that seen. Could we interpose the substance to which some
English cheeks owe their bloom in the path of a beam passing through
a prism, we should probably find the orange and yellow and green of
the prismatic spectrum more or less absorbed, the red and a portion
of the blue being transmitted. This would give us a purplish blush
resembling that of the permanganate of potash, commonly called the
mineral chameleon, a solution of which acts upon the spectrum in the
manner just described. Inasmuch, then, as we can calculate with perfect
exactness the mechanical value of the total light which falls upon the
epidermis, a certain fraction of this will express the mechanical value
of the cheek’s colour. We do not therefore jest, but speak the words of
truth and soberness when we affirm that the rays to which the tinting
of any given cheek is due would, if mechanically applied, be competent
to move a wheelbarrow through a certain space, or to lift a scuttle of
coals to a certain calculable elevation.
But the human face and eyes flush at times with a radiance which
might well be taken for a direct spiritual emanation entirely
independent of ‘brute matter.’ Let us examine this point a little.
Musical instruments, and also the human voice, have a peculiarity as
regards their sounds which differs from mere pitch. A clarionet and
a violin, for example, may be both pitched to the same note, but a
listener who sees neither can at once tell that the _qualities_
of the notes are different. This difference is what the French call
_timbre_, and the Germans, we believe, _Klang_. So, also, we
can distinguish one vowel from another, though all may have the same
pitch. The difference here, according to the recent investigations of
Helmholtz, is due to the fact that certain incidental notes commingle
in each case with the principal one, and produce a composite result.
The ‘harmonics’ of a string are known to be due to minor vibrations
which superpose themselves upon the principal ones, as small ripples
cover parasitically the surfaces of large sea-waves. The notes of the
true simple wave and of its parasites are heard at once, and it is the
variation of the latter which produces differences in the _timbre_
of a musical instrument or of the human voice.
In speculating on those more subtle phases of expression to which we
have above referred, might we not offer the conjecture that they are
not due to those waves alone which make the eyes violet or give the
cheek its rose, but are a result produced by the compounding of these
with incidental waves, which influence the colour as the harmonic
waves of sound influence the pure quality of a note? We have often
watched with deep interest and sympathy the countenances of some of
the praying women in the churches of the Continent. We have seen a
penitent kneeling at a distance from the shrine of the Virgin, as if
afraid to come nearer. Suddenly a glow has overspread her countenance,
strengthening in radiance, till at length her very soul seemed shining
through her features. Sure of her acceptance, she has confidently
advanced, fallen prostrate immediately in front of the image, and
remained therefor a time in silent ecstasy. We have watched the ebbing
of the spiritual tide, and remarked the felicitous repose which it left
behind. At each new phase of emotion the _timbre_ of this woman’s
countenance changed, and
The music breathing from her face
became altered in quality.
The tendency of the above remarks is to show that the most subtle
phases of ‘expression’ have at least a proximate mechanical origin.
The splendours of the ‘imperial Eleänore’--the ‘languors of her love
deep eyes’--are all reducible to the same cause; and not only so, but
they actually exist for a time in space, isolated alike from her and
her worshipper. Every gleam of those eyes, every flush of her brows,
every motion of her lips requires the ether for its transmission, and
a certain calculable time to pass from her to him. During this time,
the expression which is to stir the soul, to kindle love or quench it,
exists in space as a purely mechanical affection of matter; and, for
aught we know, a slight steepness in the front of an ethereal billow, a
slight curl of its crest, or some other accident of form, may determine
whether the recipient of its shock is to be elated with joy or steeped
in misery.
The philosophy of the future will assuredly take more account than
that of the past of the relation of thought and feeling to physical
processes; and it may be that the qualities of the mind will be studied
through the organism as we now study the character of a force through
the affections of ordinary matter. We believe that every thought and
every feeling has its definite mechanical correlative--that it is
accompanied by a certain separation and remarshalling of the atoms
of the brain. This latter process is purely physical; and were the
faculties we now possess sufficiently strengthened, without the
creation of any new faculty, it would doubtless be within the range of
our augmented powers to infer from the molecular state of the brain
the character of the thought acting on it, and conversely to infer
from the thought the exact molecular condition of the brain. We do not
say--and this, as will be seen, is all-important--that the inference
here referred to would be an _à priori_ one. But by observing,
with the faculties we assume, the state of the brain and the associated
mental affections, both might be so tabulated side by side that, if
one were given, a mere reference to the table would declare the other.
Our present powers, it is true, shrivel into nothingness when brought
to bear on such a problem, but it is because of its complexity and our
limits that this is the case. The _quality_ of the problem and the
_quality_ of our powers are, we believe, so related, that a mere
expansion of the latter would enable them to cope with the former. Why,
then, in scientific speculation should we turn our eyes exclusively to
the humble past? May it not be that a time is coming--ages no doubt
distant, but still advancing--when the dwellers upon earth, starting
from the gross human brain of to-day as a rudiment, may be able to
apply to these mighty questions faculties of commensurate extent? Given
the requisite expansibility to the present senses and intelligence of
man--given also the time necessary for their expansion--and this high
goal may be attained. Development is all that is required, and not
a change of quality. There need be no absolute breach of continuity
between us and our loftier brothers yet to come.
We have guarded ourselves against saying that the inferring of thought
from material combinations and arrangements would be an inference _à
priori_. The inference meant would be the same in kind as that
which the observation of the effects of food and drink upon the mind
would enable us to make, differing only from the latter in the degree
of analytical insight which we suppose attained. Given the masses and
distances of the planets, we can infer the perturbations consequent on
their mutual attractions. Given the nature of a disturbance in water,
air, or ether--from the physical qualities of the medium we can infer
how its particles will be affected. Here the mind runs with certainty
along the line of thought which connects the phenomena, and from
beginning to end finds no break in the chain. But when we endeavour to
pass by a similar process from the phenomena of physics to those of
thought, we meet a problem which transcends any conceivable expansion
of the powers which we now possess. We may think over the subject again
and again, but it eludes all intellectual presentation. We stand at
length face to face with the Incomprehensible. The territory of physics
is wide, but it has its limits from which we look with vacant gaze into
the region beyond. Whence come we; whither go we? The question dies
without an answer--without even an echo--upon the infinite shores of
the Unknown. Let us follow matter to its utmost bounds; let us claim
it in all its forms to experiment with and to speculate upon. Casting
the term ‘vital force’ from our vocabulary, let us reduce, if we can,
the visible phenomena of life to mechanical attractions and repulsions.
Having thus exhausted physics, and reached its very rim, the real
mystery still looms beyond us. We have, in fact, made no step towards
its solution. And thus it will ever loom--ever beyond the bourne of
knowledge--compelling the philosophies of successive ages to confess
that
We are such stuff
As dreams are made of, and our little life
Is rounded with a sleep.
FOOTNOTES:
[Footnote 1: One of my critics remarks, that he does not see the wit
of calling Goethe’s ‘Farbenlehre’ and Bain’s ‘Logic,’ ‘two volumes of
poetry.’ Nor do I.]
[Footnote 2: Induction, page 422.]
[Footnote 3: This glass, by reflected light, had a colour ‘strongly
resembling that of a decoction of horse-chestnut bark.’ Curiously
enough Goethe refers to this very decoction:--‘Man nehme einen Streifen
frischer Rinde von der Rosskastanie, man stecke denselben in ein
Glas Wasser, und in der kürzesten Zeit werden wir das vollkommenste
Himmelblau entstehen sehen.’--Goethe’s _Werke_, b. xxix. p. 24.]
[Footnote 4: A resolute scrutiny of the experiments, recently executed
with reference to this question, is sure to yield instructive results.]
[Footnote 5: Sir William Thomson.]
[Footnote 6: In the ‘Prefatory Letter’ to his ‘Lay Sermons,’ Mr.
Huxley speaks of ‘microscopists, ignorant alike of Philosophy and
Biology.’ With reference to one conspicuous member of this class, a
doctor of medicine, lately professor in a London college famous for its
orthodoxy, both Mr. Huxley and myself have long practised, and shall, I
trust, continue to practise, the tolerance recommended above.]
[Footnote 7: An Address to the Mathematical and Physical Section of the
British Association assembled at Norwich on August 19, 1868.]
[Footnote 8: From an article headed ‘Physics and Metaphysics,’ in the
_Saturday Review_ for August 4, 1860.]
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