hemisphere are at this moment insensibly rising and others insensibly
sinking; and there is indirect, but perfectly satisfactory, proof, that
an enormous area now covered by the Pacific has been deepened thousands
of feet, since the present inhabitants of that sea came into existence.
Thus there is not a shadow of a reason for believing that the physical
changes of the globe, in past times, have been effected by other than
natural causes.
CXCVIII
A small beginning has led us to a great ending. If I were to put the bit
of chalk with which we started into the hot but obscure flame of burning
hydrogen, it would presently shine like the sun. It seems to me that
this physical metamorphosis is no false image of what has been the
result of our subjecting it to a jet of fervent, though nowise
brilliant, thought to-night. It has become luminous, and its clear rays,
penetrating the abyss of the remote past, have brought within our ken
some stages of the evolution of the earth. And in the shifting "without
haste, but without rest" of the land and sea, as in the endless
variation of the forms assumed by living beings, we have observed
nothing but the natural product of the forces originally possessed by
the substance of the universe.
CXCIX
In certain parts of the sea bottom in the immediate vicinity of the
British Islands, as in the Clyde district, among the Hebrides, in the
Moray Firth, and in the German Ocean, there are depressed areae, forming
a kind of submarine valleys, the centres of which are from 80 to 100
fathoms, or more, deep. These depressions are inhabited by assemblages
of marine animals, which differ from those found over the adjacent and
shallower region, and resemble those which are met with much farther
north, on the Norwegian coast. Forbes called these Scandinavian
detachments "Northern outliers."
How did these isolated patches of a northern population get into these
deep places? To explain the mystery, Forbes called to mind the fact
that, in the epoch which immediately preceded the present, the climate
was much colder (whence the name of "glacial epoch" applied to it); and
that the shells which are found fossil, or sub-fossil, in deposits of
that age are precisely such as are now to be met with only in the
Scandinavian, or still more Arctic, regions. Undoubtedly, during the
glacial epoch, the general population of our seas had, universally, the
northern aspect which is now presented only by the "northern outliers";
just as the vegetation of the land, down to the sea-level, had the
northern character which is, at present, exhibited only by the plants
which live on the tops of our mountains. But, as the glacial epoch
passed away, and the present climatal conditions were developed, the
northern plants were able to maintain themselves only on the bleak
heights, on which southern forms could not compete with them. And, in
like manner, Forbes suggested that, after the glacial epoch, the
northern animals then inhabiting the sea became restricted to the deeps
in which they could hold their own against invaders from the south,
better fitted than they to flourish in the warmer waters of the
shallows. Thus depth in the sea corresponded in its effect upon
distribution to height on the land.
CC
Among the scientific instructions for the voyage[2] drawn up by a
committee of the Royal Society, there is a remarkable letter from Von
Humboldt to Lord Minto, then First Lord of the Admiralty, in which,
among other things, he dwells upon the significance of the researches
into the microscopic composition of rocks, and the discovery of the
great share which microscopic organisms take in the formation of the
crust of the earth at the present day, made by Ehrenberg in the years
1836-39. Ehrenberg, in fact, had shown that the extensive beds of
"rotten-stone" or "Tripoli" which occur in various parts of the world,
and notably at Bilin in Bohemia, consisted of accumulations of the
silicious cases and skeletons of _Diatomaceae_, sponges, and
_Radiolaria_; he had proved that similar deposits were being formed by
_Diatomaceae_, in the pools of the Thiergarten in Berlin and elsewhere,
and had pointed out that, if it were commercially worth while,
rotten-stone might be manufactured by a process of diatom-culture.
Observations conducted at Cuxhaven, in 1839, had revealed the existence,
at the surface of the waters of the Baltic, of living Diatoms and
_Radiolaria_ of the same species as those which, in a fossil state,
constitute extensive rocks of tertiary age at Caltanisetta, Zante, and
Oran, on the shores of the Mediterranean.
[2] Of the _Challenger_.
Moreover, in the fresh-water rotten-stone beds of Bilin, Ehrenberg had
traced out the metamorphosis, effected apparently by the action of
percolating water, of the primitively loose and friable deposit of
organized particles, in which the silex exists in the hydrated or
soluble condition. The silex, in fact, undergoes solution and slow
redeposition, until, in ultimate result, the excessively fine-grained
sand, each particle of which is a skeleton, becomes converted into a
dense opaline stone, with only here and there an indication of an
organism.
From the consideration of these facts, Ehrenberg, as early as the year
1839, had arrived at the conclusion that rocks, altogether similar to
those which constitute a large part of the crust of the earth, must be
forming, at the present day, at the bottom of the sea; and he threw out
the suggestion that even where no trace of organic structure is to be
found in the older rocks, it may have been lost by metamorphosis.
CCI
It is highly creditable to the ingenuity of our ancestors that the
peculiar property of fermented liquids, in virtue of which they "make
glad the heart of man," seems to have been known in the remotest periods
of which we have any record. All savages take to alcoholic fluids as if
they were to the manner born. Our Vedic forefathers intoxicated
themselves with the juice of the "soma"; Noah, by a not unnatural
reaction against a superfluity of water, appears to have taken the
earliest practicable opportunity of qualifying that which he was obliged
to drink; and the ghosts of the ancient Egyptians were solaced by
pictures of banquets in which the wine-cup passes round, graven on the
walls of their tombs. A knowledge of the process of fermentation,
therefore, was in all probability possessed by the prehistoric
populations of the globe; and it must have become a matter of great
interest even to primaeval wine-bibbers to study the methods by which
fermented liquids could be surely manufactured. No doubt it was soon
discovered that the most certain, as well as the most expeditious, way
of making a sweet juice ferment was to add to it a little of the scum,
or lees, of another fermenting juice. And it can hardly be questioned
that this singular excitation of fermentation in one fluid, by a sort of
infection, or inoculation, of a little ferment taken from some other
fluid, together with the strange swelling, foaming, and hissing of the
fermented substance, must have always attracted attention from the more
thoughtful. Nevertheless, the commencement of the scientific analysis of
the phenomena dates from a period not earlier than the first half of the
seventeenth century.
At this time, Van Helmont made a first step, by pointing out that the
peculiar hissing and bubbling of a fermented liquid is due, not to the
evolution of common air (which he, as the inventor of the term "gas,"
calls "gas ventosum"), but to that of a peculiar kind of air such as is
occasionally met with in caves, mines, and wells, and which he calls
"gas sylvestre."
But a century elapsed before the nature of this "gas sylvestre," or, as
it was afterwards called, "fixed air," was clearly determined, and it
was found to be identical with that deadly "chokedamp" by which the
lives of those who descend into old wells, or mines, or brewers' vats,
are sometimes suddenly ended; and with the poisonous aeriform fluid
which is produced by the combustion of charcoal, and now goes by the
name of carbonic acid gas.
During the same time it gradually became evident that the presence of
sugar was essential to the production of alcohol and the evolution of
carbonic acid gas, which are the two great and conspicuous products of
fermentation. And finally, in 1787, the Italian chemist, Fabroni, made
the capital discovery that the yeast ferment, the presence of which is
necessary to fermentation, is what he termed a "vegeto-animal"
substance; that is, a body which gives off ammoniacal salts when it is
burned, and is, in other ways, similar to the gluten of plants and the
albumen and casein of animals.
CCII
The living club-mosses are, for the most part, insignificant and
creeping herbs, which, superficially, very closely resemble true mosses,
and none of them reach more than two or three feet in height. But, in
their essential structure, they very closely resemble the earliest
Lepidodendroid trees of the coal: their stems and leaves are similar; so
are their cones; and no less like are the sporangia and spores; while
even in their size, the spores of the _Lepidodendron_ and those of the
existing _Lycopodium_, or club-moss, very closely approach one another.
Thus, the singular conclusion is forced upon us, that the greater and
the smaller sacs of the "Better-Bed" and other coals, in which the
primitive structure is well preserved, are simply the sporangia and
spores of certain plants, many of which were closely allied to the
existing club-mosses. And if, as I believe, it can be demonstrated that
ordinary coal is nothing but "saccular" coal which has undergone a
certain amount of that alteration which, if continued, would convert it
into anthracite; then, the conclusion is obvious, that the great mass of
the coal we burn is the result of the accumulation of the spores and
spore-cases of plants, other parts of which have furnished the
carbonized stems and the mineral charcoal, or have left their
impressions on the surfaces of the layer.
CCIII
The position of the beds which constitute the coal-measures is
infinitely diverse. Sometimes they are tilted up vertically, sometimes
they are horizontal, sometimes curved into great basins; sometimes they
come to the surface, sometimes they are covered up by thousands of feet
of rock. But, whatever their present position, there is abundant and
conclusive evidence that every under-clay was once a surface soil. Not
only do carbonized root-fibres frequently abound in these under-clays;
but the stools of trees, the trunks of which are broken off and
confounded with the bed of coal, have been repeatedly found passing into
radiating roots, still embedded in the under-clay. On many parts of the
coast of England, what are commonly known as "submarine forests" are to
be seen at low water. They consist, for the most part, of short stools
of oak, beech, and fir-trees, still fixed by their long roots in the bed
of blue clay in which they originally grew. If one of these submarine
forest beds should be gradually depressed and covered up by new
deposits, it would present just the same characters as an under-clay of
the coal, if the _Sigillaria_ and _Lepidodendron_ of the ancient world
were substituted for the oak, or the beech, of our own times.
In a tropical forest, at the present day, the trunks of fallen trees,
and the stools of such trees as may have been broken by the violence of
storms, remain entire for but a short time. Contrary to what might be
expected, the dense wood of the tree decays, and suffers from the
ravages of insects, more swiftly than the bark. And the traveller,
setting his foot on a prostrate trunk finds that it is a mere shell,
which breaks under his weight, and lands his foot amidst the insects, or
the reptiles, which have sought food or refuge within.
CCIV
The coal accumulated upon the area covered by one of the great forests
of the carboniferous epoch would, in course of time, have been wasted
away by the small, but constant, wear and tear of rain and streams, had
the land which supported it remained at the same level, or been
gradually raised to a greater elevation. And, no doubt, as much coal as
now exists has been destroyed, after its formation, in this way.
CCV
Once more, an invariably-recurring lesson of geological history, at
whatever point its study is taken up: the lesson of the almost infinite
slowness of the modification of living forms. The lines of the pedigrees
of living things break off almost before they begin to converge.
CCVI
Yet another curious consideration. Let us suppose that one of the
stupid, salamander-like Labyrinthodonts, which pottered, with much belly
and little leg, like Falstaff in his old age, among the coal-forests,
could have had thinking power enough in his small brain to reflect upon
the showers of spores which kept on falling through years and
centuries, while perhaps not one in ten million fulfilled its apparent
purpose, and reproduced the organism which gave it birth: surely he
might have been excused for moralizing upon the thoughtless and wanton
extravagance which Nature displayed in her operations.
But we have the advantage over our shovelheaded predecessor--or possibly
ancestor--and can perceive that a certain vein of thrift runs through
this apparent prodigality. Nature is never in a hurry, and seems to have
had always before her eyes the adage, "Keep a thing long enough, and you
will find a use for it." She has kept her beds of coal many millions of
years without being able to find much use for them; she has sent them
down beneath the sea, and the sea-beasts could make nothing of them; she
has raised them up into dry land, and laid the black veins bare, and
still, for ages and ages, there was no living thing on the face of the
earth that could see any sort of value in them; and it was only the
other day, so to speak, that she turned a new creature out of her
workshop, who by degrees acquired sufficient wits to make a fire, and
then to discover that the black rock would burn.
I suppose that nineteen hundred years ago, when Julius Caesar was good
enough to deal with Britain as we have dealt with New Zealand, the
primaeval Briton, blue with cold and woad, may have known that the
strange black stone, of which he found lumps here and there in his
wanderings, would burn, and so help to warm his body and cook his food.
Saxon, Dane, and Norman swarmed into the land. The English people grew
into a powerful nation, and Nature still waited for a full return of the
capital she had invested in the ancient club-mosses. The eighteenth
century arrived, and with it James Watt. The brain of that man was the
spore out of which was developed the modern steam-engine, and all the
prodigious trees and branches of modern industry which have grown out
of this. But coal is as much an essential condition of this growth and
development as carbonic acid is for that of a club-moss. Wanting coal,
we could not have smelted the iron needed to make our engines, nor have
worked our engines when we had got them. But take away the engines, and
the great towns of Yorkshire and Lancashire vanish like a dream.
Manufactures give place to agriculture and pasture, and not ten men can
live where now ten thousand are amply supported.
Thus, all this abundant wealth of money and of vivid life is Nature's
interest upon her investment in club-mosses, and the like, so long ago.
But what becomes of the coal which is burnt in yielding this interest?
Heat comes out of it, light comes out of it; and if we could gather
together all that goes up the chimney, and all that remains in the grate
of a thoroughly-burnt coal-fire, we should find ourselves in possession
of a quantity of carbonic acid, water, ammonia, and mineral matters,
exactly equal in weight to the coal. But these are the very matters with
which Nature supplied the club-mosses which made the coal. She is paid
back principal and interest at the same time; and she straightway
invests the carbonic acid, the water, and the ammonia in new forms of
life, feeding with them the plants that now live. Thrifty Nature! Surely
no prodigal, but most notable of housekeepers!
CCVII
Here, then, is a capital fact. The movements of the lobster are due to
muscular contractility. But why does a muscle contract at one time and
not at another? Why does one whole group of muscles contract when the
lobster wishes to extend his tail, and another group when he desires to
bend it? What is it originates, directs, and controls the motive power?
Experiment, the great instrument for the ascertainment of truth in
physical science, answers this question for us. In the head of the
lobster there lies a small mass of that peculiar tissue which is known
as nervous substance. Cords of similar matter connect this brain of the
lobster, directly or indirectly, with the muscles. Now, if these
communicating cords are cut, the brain remaining entire, the power of
exerting what we call voluntary motion in the parts below the section is
destroyed; and, on the other hand, if, the cords remaining entire, the
brain mass be destroyed, the same voluntary mobility is equally lost.
Whence the inevitable conclusion is, that the power of originating these
motions resides in the brain and is propagated along the nervous cords.
In the higher animals the phenomena which attend this transmission have
been investigated, and the exertion of the peculiar energy which resides
in the nerves has been found to be accompanied by a disturbance of the
electrical state of their molecules.
If we could exactly estimate the signification of this disturbance; if
we could obtain the value of a given exertion of nerve force by
determining the quantity of electricity, or of heat, of which it is the
equivalent; if we could ascertain upon what arrangement, or other
condition of the molecules of matter, the manifestation of the nervous
and muscular energies depends (and doubtless science will some day or
other ascertain these points), physiologists would have attained their
ultimate goal in this direction; they would have determined the relation
of the motive force of animals to the other forms of force found in
nature; and if the same process had been successfully performed for all
the operations which are carried on in, and by, the animal frame,
physiology would be perfect, and the facts of morphology and
distribution would be deducible from the laws which physiologists had
established, combined with those determining the condition of the
surrounding universe.
CCVIII
The object of lectures is, in the first place, to awaken the attention
and excite the enthusiasm of the student; and this, I am sure, may be
effected to a far greater extent by the oral discourse and by the
personal influence of a respected teacher than in any other way.
Secondly, lectures have the double use of guiding the student to the
salient points of a subject, and at the same time forcing him to attend
to the whole of it, and not merely to that part which takes his fancy.
And lastly, lectures afford the student the opportunity of seeking
explanations of those difficulties which will, and indeed ought to,
arise in the course of his studies.
CCIX
What books shall I read? is a question constantly put by the student to
the teacher. My reply usually is, "None: write your notes out carefully
and fully; strive to understand them thoroughly; come to me for the
explanation of anything you cannot understand; and I would rather you
did not distract your mind by reading." A properly composed course of
lectures ought to contain fully as much matter as a student can
assimilate in the time occupied by its delivery; and the teacher should
always recollect that his business is to feed and not to cram the
intellect. Indeed, I believe that a student who gains from a course of
lectures the simple habit of concentrating his attention upon a
definitely limited series of facts, until they are thoroughly mastered,
has made a step of immeasurable importance.
CCX
However good lectures may be, and however extensive the course of
reading by which they are followed up, they are but accessories to the
great instrument of scientific teaching--demonstration. If I insist
unweariedly, nay fanatically, upon the importance of physical science as
an educational agent, it is because the study of any branch of science,
if properly conducted, appears to me to fill up a void left by all other
means of education. I have the greatest respect and love for literature;
nothing would grieve me more than to see literary training other than a
very prominent branch of education: indeed, I wish that real literary
discipline were far more attended to than it is; but I cannot shut my
eyes to the fact that there is a vast difference between men who have
had a purely literary, and those who have had a sound scientific,
training.
CCXI
In the world of letters, learning and knowledge are one, and books are
the source of both; whereas in science, as in life, learning and
knowledge are distinct, and the study of things, and not of books, is
the source of the latter.
CCXII
All that literature has to bestow may be obtained by reading and by
practical exercise in writing and in speaking; but I do not exaggerate
when I say that none of the best gifts of science are to be won by these
means. On the contrary, the great benefit which a scientific education
bestows, whether as training or as knowledge, is dependent upon the
extent to which the mind of the student is brought into immediate
contact with facts--upon the degree to which he learns the habit of
appealing directly to Nature, and of acquiring through his senses
concrete images of those properties of things, which are, and always
will be, but approximatively expressed in human language. Our way of
looking at Nature, and of speaking about her, varies from year to year;
but a fact once seen, a relation of cause and effect, once
demonstratively apprehended, are possessions which neither change nor
pass away, but, on the contrary, form fixed centres, about which other
truths aggregate by natural affinity.
Therefore, the great business of the scientific teacher is, to imprint
the fundamental, irrefragable facts of his science, not only by words
upon the mind, but by sensible impressions upon the eye, and ear, and
touch of the student, in so complete a manner, that every term used, or
law enunciated, should afterwards call up vivid images of the particular
structural, or other, facts which furnished the demonstration of the
law, or the illustration of the term.
CCXIII
What is the purpose of primary intellectual education? I apprehend that
its first object is to train the young in the use of those tools
wherewith men extract knowledge from the ever-shifting succession of
phenomena which pass before their eyes; and that its second object is to
inform them of the fundamental laws which have been found by experience
to govern the course of things, so that they may not be turned out into
the world naked, defenceless, and a prey to the events they might
control.
A boy is taught to read his own and other languages, in order that he
may have access to infinitely wider stores of knowledge than could ever
be opened to him by oral intercourse with his fellow men; he learns to
write, that his means of communication with the rest of mankind may be
indefinitely enlarged, and that he may record and store up the knowledge
he acquires. He is taught elementary mathematics, that he may understand
all those relations of number and form, upon which the transactions of
men, associated in complicated societies, are built, and that he may
have some practice in deductive reasoning.
All these operations of reading, writing, and ciphering are intellectual
tools, whose use should, before all things, be learned, and learned
thoroughly; so that the youth may be enabled to make his life that which
it ought to be, a continual progress in learning and in wisdom.
CCXIV
In addition, primary education endeavours to fit a boy out with a
certain equipment of positive knowledge. He is taught the great laws of
morality; the religion of his sect; so much history and geography as
will tell him where the great countries of the world are, what they are,
and how they have become what they are.