Chapter III: Spiritual or Moral Development (3)

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 reflection 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
ærial 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 color 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 color
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 color. The other colors
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 analyzed all the colors 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 skeptical “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 color through the operation of the same cause; and Helmholtz
has irreverently disclosed the fact that a blue eye is simply a
turbid medium.

Numerous instances of the kind might be cited. The action of turbid
media upon light was fully and beautifully illustrated by Goethe,
who, though unacquainted with the undulatory theory, was led by his
experiments to regard the blue of the firmament as caused by 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. 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. No doubt the blueness
of certain Alpine lakes is in part due to this cause. Professor
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 favorably
observed, exhibits at a certain stage of its condensation the colors
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 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 colored
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 inquiries forward. Our best microscopes can readily reveal
objects not more than 1/50000 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 1/100000 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 behooves 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
color 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 eye 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
resin in Brücke’s medium, and when you have done so follow me. I
permitted a beam of light to act upon a certain vapor. 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
color 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
1/100000 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?
As the distances of stellar space give us simply a bewildering sense
of vastness without leaving any distinct impression on the mind, so
the magnitudes with which we have here to do impress us with a
bewildering sense of smallness. 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, then, to surround the earth at a
hight above the surface which would place it beyond the grosser
matter that hangs in the lower regions of the air—say at the hight
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 snuff-box—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 hight 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 this light? On points of controversy I will not here
enter, but I may say that 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. 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 travelers 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 conception of atoms and molecules to which we have so
frequently referred, a bit of matter, say 1/50000 of an inch in
diameter, will present itself differently. The one descends to it
from his molar hights, 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 defense and startling expansion of the doctrine will
appear perfectly conclusive, to the other it will present itself as
imposing a profitless labor of demolition on subsequent
investigators. The proper and possible attitude of these two men is
that each of them should work as if it were his aim and object to
establish the view entertained by the other.

I trust, Mr. President, that you—whom untoward circumstances have
made a biologist, but who still keep alive your sympathy with that
class of inquiries 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° F., 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 here present, 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
polarization 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 microscopic 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 marshaling 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 inquiry lies an immense
field for the exercise of the imagination. 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 pan-genesis. 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 favor 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 as 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 inquire into
the history of its genesis.

Certainty is here hopeless, but the materials for an opinion may be
attainable. In this dim twilight of speculation the inquirer
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 imagination
in the antecedent ages and worlds. And though the certainty
possessed by experimental inquiry 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 civilization of Egypt in the time of
Joseph; pointing out that the very perfect organization of the
kingdom, and the possession of chariots, in one of which Joseph
rode, indicated a long antecedent period of civilization. He then
passed on to the mud of the Nile, its rate of augmentation, its
present thickness, and the remains of human handiwork found therein;
thence to the rocks which bound the Nile valley, and which team 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-humoredly 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.

In fact, clergymen, if I might be allowed a parenthesis to say so,
have as strong a leaning towards scientific truth as other men, only
the resistance to this bent—a resistance due to education—is
generally stronger in their case than in others. They do not lack
the positive element, namely, the love of truth, but the negative
element, the fear of error, preponderates.

The strength of an electric current is determined by two things—the
electro-motive force, and the resistance that force has to overcome.
A fraction, with the former as numerator and the latter as
denominator, expresses the current-strength. The “current-strength”
of the clergy towards science may also be expressed by making the
positive element just referred to the numerator, and the negative
one the denominator of a fraction. The numerator is not zero nor is
it even small, but the denominator is large; and hence the current
strength is such as we find it to be. Slowness of conception, even
open hostility, may be thus accounted for. They are for the most
part errors of judgment, and not sins against truth. To most of us
it may appear very simple, but to a few of us it appears
transcendently wonderful, that in all classes of society truth
should have this power and fascination. From the countless
modifications that life has undergone through natural selection and
the integration of infinitesimal steps, emerges finally the grand
result that the strength of truth is greater than the strength of
error, and that we have only to make the truth clear to the world to
gain the world to our side. Probably no one wonders more at this
result than the propounder of the law of natural selection himself.
Reverting to an old acquaintance of ours, it would seem, on purely
scientific grounds, as if a Veracity were at the heart of things; as
if, after ages of latent working, it had finally unfolded itself in
the life of man; as if it were still destined to unfold itself,
growing in girth, throwing out stronger branches and thicker leaves,
and tending more and more by its overshadowing presence to starve
the weeds of error from the intellectual soil.

But this is parenthetical; and the gist of our present inquiry
regarding the introduction of life is this: Does it belong to what
we call matter, or is it an independent principle inserted into
matter at some suitable epoch—say when the physical conditions
become 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
theater 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 a 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 motion 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, Shakespeare, 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
spirit and matter is: “What God hath joined together let not man put
asunder.”

I have thus led you to the outer rim of speculative science, for
beyond the nebula 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 neither of these
things.

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 naught.” Under the
fierce light of scientific inquiry this hypothesis is sure to be
dissipated if it possess not a core of truth. Trust me, its
existence as an 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 untouched. At bottom it does nothing more
than “transport the conception of life’s origin to an indefinitely
distant past.”

For, granting the nebula and its potential life, the question,
whence came they? would still remain to baffle and bewilder us. And
with regard to the ages of forgetfulness which lie between the
conscious life of the nebula and the conscious life of the earth, it
is but an extension of that forgetfulness which preceded the birth
of us all. 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 inquiry 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 this 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 which _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.