Individuals of whatever kind, or however numerous, are of no estimation
in the universe; it is species alone that are existences in Nature,
for they are as ancient and permanent as herself. To have a clear
and distinct idea of this subject we must not consider a species as
a collection or succession of similar individuals, but as a whole,
independently of number or time, always active, and always the same;
a whole which was considered but as one in the works of the creation,
and therefore constitutes only a unit in Nature. Of these units the
human species is to be placed in the first rank; all the others, from
the elephant to the mite, from the cedar to the hyssop, belong to
the second and third orders. Notwithstanding that they are different
in form, substance, and even life, yet each sustains its appointed
destination, and subsists independently of others, while the whole, in
a general view, represents animated Nature, who has hitherto supported,
and will continue to support, herself in the same manner as she is seen
at present. Her duration is not to be estimated by a day, a year, an
age, nor any given period of time, for time itself relates only to
individuals, to beings whose existence is limited. It is not so with
respect to species, for their existence is constant; their permanence
produces duration, and their differences give rise to number. It is
in this light that we must consider species, and give to each an
equal right to the indulgence and support of Nature; for so _she_ has
certainly considered them, by bestowing on each the means of existing
as long as herself.
Let us now consider the species as having changed places with the
individual. In our preceding observations we have seen the relation
which Nature holds in respect to man; let us now then take a view
in what light she would appear to a being who represented the whole
human species. We perceive that in the spring the fields renew their
verdure, the buds and flowers expand, the bees revive from their
state of torpor, the swallows return to our climates, the nightingale
chaunts her song of love, the lamb frisks, and the bull laws with
desire, and all animated creatures are eager to unite and multiply
their species; and we can then have no ideas but those of reproduction
and the increase of life. But when the dark season of cold and frost
approaches, these same beings become indifferent to and avoid each
other; many of the feathered race desert our clime, and the inhabitants
of the waters lose their freedom under the massy congelations of ice;
various animals dig retreats for themselves in the ground, where they
fall into a state of torpor; the earth becomes hard, the plants wither,
and the trees, deprived of their foliage, are covered with frost and
snow; every object excites the idea of languor and annihilation.
These appearances, however, of renovation and destruction, images,
as it were, of life and death, although they seem general, are only
individual and particular. Man, as an individual, concludes in this
manner, but the being whom we have supposed as a representative of the
species, thinks and judges in a manner more exalted and general; in
that constant succession of destruction and renovation, and in those
various vicissitudes, he perceives only permanence and duration. The
different seasons in one year appear to him the same as those of the
preceding, the same as those of millions of ages. The animal which may
be the thousandth in the order of generation is the same to him as the
first. In a word, if man had no period to his existence, and if all
the beings by which he is surrounded existed in the same manner as they
do at present, the idea of time would vanish and the individual would
in fact become the species.
Let us then consider Nature for a few moments under this new aspect.
Man certainly comes into the world enveloped in darkness. His mind is
equally naked with his body; he is born without knowledge and without
defence, and brings nothing with him but passive qualities. He is
compelled to receive the impressions of objects on his organs; even
the light shines on his eyes long before he is able to recognize it.
To Nature he is at first indebted for every thing, without making her
any return. No sooner, however, do his senses acquire strength and
activity, and he can compare his sensations, than he reflects upon the
universe; he forms ideas, which he retains, extends, and combines. Man,
after receiving instruction, is no longer a simple individual, for
he then, in a great measure, represents the whole human species. He
receives from his parents the knowledge which had been transmitted to
them from their forefathers; and thus, by the divine arts of writing
and printing, the present age, in some sort, becomes identified with
those that are past. This accumulation of experience in one man, almost
extends the limits of his being to infinity. He is born no more than
a simple individual, like other animals, capable only of attending to
present sensations; but he becomes afterwards nearly the being which
we supposed to represent the whole species; he reads what has past,
sees the present, and judges of the future; and in the torrent of time,
which carries off and absorbs all the individuals of the universe,
he perceives that the species are permanent, and Nature invariable.
As the relations of objects are always the same, to him the order of
time appears to be nothing; he considers the laws of renovation as
only counterbalancing those of permanency. An uninterrupted succession
of similar beings, is, in effect, only equivalent to the perpetual
existence of one of them.
What purposes then are gained by this immense train of generations,
this profusion of germs, many thousands of which are abortive for one
that is brought into life? Does not this perpetual propagation of
beings, which are alternately destroyed and renewed, uniformly exhibit
the same scene, and occupy the same proportion in Nature? From what
cause proceed all these changes of life and death, these laws of
growth and decay, all these individual vicissitudes, and reiterated
representations of the same identical thing? They certainly arise from
the very essence of Nature, and depend on the first establishment of
the universal machine; the whole of which is fixed and stable, but
each of its parts being endowed with the power of motion, the general
movements of the celestial bodies have produced the particular ones of
this terrestrial globe. The penetrating forces by which these immense
bodies are animated, and by which they act reciprocally upon each other
at a distance, at the same time animate every particle of matter; and
this strong propensity, which every part has towards each other, is
the first bond of beings, the ground of consistence and permanency in
Nature, and the support of harmony in the universe. From these great
combinations the smaller relations are derived. The earth moving on
its own axis having separated the portions of duration into day and
night; all its animated inhabitants have their stated periods of light
and darkness, of their times of waking and sleeping. The action of the
senses, and the motions of the members which form a great part of the
animal economy, are related to this first combination; for in a world
where perpetual darkness reigned, would there be senses alive to the
enjoyment of light.
As the inclination of the axis of the earth, in its annual course round
the sun, produces considerable variations of heat and cold, which we
call seasons, all its vegetables have also, either wholly or partially,
their seasons of life and death. The fall of the leaves, and the decay
of fruits, the withering of herbs and the destruction of insects,
depend entirely on this second combination. In those climates where
there is not this variation, by the inclination not being so material,
the life of the vegetable is not suspended, and every insect completes
the stated period of its existence. Where the four seasons, in fact,
make but one, as under the line, the surface of the earth is constantly
covered with flowers, the trees have a perpetual foliage, and Nature
seems to enjoy a continual spring.
Both in animals and plants, their particular constitution is relatively
to the general temperature of the earth, and which temperature depends
upon its situation and distance from the sun. If they were removed to
a greater distance, neither our animals, nor our plants, could live or
vegetate; the water, sap, blood, and all their liquors, would lose
their fluidity; if on the contrary they were more near they would
vanish and dissipate in vapour. Ice and fire are the elements of death,
and temperate heat the first support of life. The living particles so
generally diffused through all organized bodies are related, not only
by their activity but number, to the particles of light which strike
and penetrate almost all matter with their heat; for in every place
where the sun can heat the earth with its rays, the surface will be
covered with verdure, and peopled with animals; even ice is no sooner
dissolved into water than it swarms with inhabitants. Water, indeed, is
apparently more fertile than the earth; from heat it receives motion
and life. In one season the sea produces more animals than the earth
sustains; but its production of vegetables is infinitely less. And
because that the inhabitants of the ocean have not a sufficient and
permanent supply of vegetables, they are compelled to feed upon each
other; and it is to this necessity that their immense multiplication
may be referred.
As in the beginning every species was created, the first individual
of each has served for a model to their descendants. The body of each
animal or vegetable is a mould, to which are assimilated indifferently
the organic particles of all animals or vegetables which have been
destroyed by death, or consumed by time. The brute particles, of which
part of their composition was formed, returned to the common mass
of inanimate matter; but the organic particles, whose existence is
permanent, are again resumed by organized bodies: they are extracted at
first from the earth by vegetables, and then absorbed by animals who
feed thereon; and thus serve for the support, growth, and expansion of
both. By this constant and perpetual circulation from body to body,
they serve to animate all organized beings. These living substances in
quantity are always the same, and differ only in form and appearance.
In fertile ages, and when population is the greatest, the whole surface
of the earth seems to be covered with men, domestic animals, and useful
plants. But in the times of famine and depopulation, the ferocious
animals, poisonous insects, parasitical plants, and useless herbs,
resume, in their turn, dominion over the earth. To man these changes
are material, but to Nature they are perfectly indifferent. The silk
worm so inestimable to the former, is to the latter only a caterpillar
of the mulberry tree. Though this caterpillar, which so materially
assists in the supply of our luxuries, should disappear; though the
plants, from which our domestic animals procure their nourishment,
should be devoured by other caterpillars; though still others should
destroy the substance of our corn before the harvest; in short, though
man and the larger animals should be starved by the inferior tribes,
Nature would not be less abundant nor less alive; she never protects
one at the expence of another, but especially supports the whole. As
to individuals she is regardless of number; she considers them only as
successive images of the same impression; as passing shadows of which
the species is the substance.
In earth, air, and water, then, there exists a certain quantity of
organic matter which cannot be destroyed, but which is constantly
assimilated in a certain number of moulds, that are perpetually
undergoing destruction and renewal: these moulds, or rather
individuals, tho' varying in number in every species, are nevertheless
always the same, that is, proportioned to the quantity of living
matter; and this appears to be absolutely the case, for if there were
any redundance of this matter, or if it were not at all times fully
occupied by the individuals of the species which exist, it would, most
assuredly, form itself into new species, for being alive it would not
remain without action; and once uniting with brute matter is sufficient
to form organized bodies; and it is by this constant combination, and
invariable proportion, that Nature preserves her form and consistence.
The laws of Nature, both with respect to the number of species and of
their support and equilibrium, being fixed and constant, she would
invariably have the same appearance, and be in all climes absolutely
the same, if her complexion did not so completely vary in almost every
individual form. The figure of each species is an impression, in which
the principal characters are so strongly engraven as never to be
effaced; but the accessory parts and shades are so greatly varied that
no two individuals have a perfect resemblance to each other; and in all
species there are a number of varieties. The human species, which has
such superior pretensions, varies from white to black, from small to
great, &c. The Laplander, the Patagonian, the Hottentot, the European,
the American, and the Negro, though the offspring of the same parents,
have by no means the resemblance of brothers.
It is evident, therefore, that every species is subject to individual
differences, but that each of them does not equally possess the
constant varieties which are perpetuated through successive
generations; the more dignified the species, the less changeable is
its figure, and the less are the varieties of it. The multiplication
of animals being inversely in proportion to their magnitude, as the
possibility of variation must be in exact proportion to the numbers
they produce, there consequently must be more varieties among the small
than the large animals; and also, for the same reason, there will be a
greater number of species which seem to approach each other; for the
unity of the species in the large animals is more fixed, and the nature
of their separation more extended. What a number of various and similar
species surround those of the squirrel, the rat, and other small
quadrupeds, while the massy elephant stands alone, without a compeer,
and at the head of the whole.
The brute matter, of which the body of the earth is principally
composed, is a substance that has not undergone many alterations,
though the whole has more than once been disturbed and put in motion
by the hand of Nature. The globe of the earth has been penetrated by
fire, and afterwards covered and disordered by water. The sand, which
occupies the interior parts of the earth, is a vitrified matter; and
the layers of clay, by which its surface is covered, are nothing
but the same sand having been decomposed by the operation of the
waters. Granite, free-stone, flint, nay, all metals, are composed of
this same vitrified matter, whose particles have been condensed or
separated, according to the laws of their affinity. These substances
are totally destitute of animation; they exist, and will continue to
do so, independently of animals and vegetables. There are, however,
many other substances, which, although they have the appearance of
being equally inanimate, originate from organized bodies; and of
this description are marble, lime-stone, chalk, and marl; they being
composed of the fragments of shells, and of those small animals which
by transforming the water of the sea into stone, produce coral, and
all the madrepores, whose varieties are numberless, and whose quantity
are almost immense. Pit-coal, turf, and many other substances found in
the upper strata, are also of this nature, they being only the residue
of vegetables which have been more or less corrupted or consumed.
Besides these, there are other substances which have been produced
by the second action of fire upon original matter; these are but few
in number, and consist of such as pumice-stones, sulphur, the scoria
of iron, asbestos, and lava. To one or other of these three great
combinations may be referred all the relations of brute matter, and all
the substances of the mineral kingdom.
The laws of affinity, by which the various particles of these different
substances separate from each other, in order to unite among themselves
and form homogeneous masses, are perfectly similar to that general law
by which the celestial bodies act upon each other; in both cases their
exertions are the same. Globules of water, of sand, or of metal, have
the same influence, and act upon each other as the earth acts upon the
moon; and if the laws of affinity have hitherto been deemed different
from those of gravity, it is because the subject has been considered in
a very confined point of view. The mutual action of celestial bodies
is very little influenced by figure; their distance from each other
is so very great, that this is necessarily the case; but when they
are not far asunder, then the effect of figure is considerable. For
instance, if the earth and moon, instead of spherical figures, were
both short cylinders, and exactly equal throughout in their diameters,
their reciprocal action would be very little varied from what it is at
present, because the distances of all their parts from each other would
be very little changed. But if these two globes were cylinders of great
extent, and approached near to each other, the law of their reciprocal
action would seem to be different, inasmuch as the distances of their
parts would be greatly varied; and hence whenever figure becomes a
principle in distance the law will appear to vary, although in fact it
is always the same.
The human intellect guided by this principle, may advance one step
further in penetrating into the operations of nature. The figure of
the constituent particles of bodies still remains unknown; we cannot
entertain the smallest doubt that water, air, earth, metals, and all
homogeneous particles, are composed of elementary particles, which are
perfectly similar, although we are still ignorant of their figure. By
the aid of calculation this at present unknown field of knowledge may
be disclosed by posterity, and the figure of the elementary bodies be
ascertained with tolerable precision. They may take the principle we
have established as the basis of their enquiry; namely, "that all
matter is attracted in the inverse ratio of the square of the distance;
and this law seems to admit of no variation in particular attractions
but what arises from the figure of the constituent particles of each
substance, because this figure enters as an element or principle into
the distance;" and having once discovered, by repeated experiments,
the law of attraction in any particular substance, they may then, by
the aid of calculation, be able to trace the figure of its constituent
particles. To render this point more clear, let us suppose, that by
placing mercury on a perfectly polished surface, repeated experiments
prove that this fluid metal is always attracted in the inverse ratio of
the cube of the distance; it will then become necessary to investigate
what figure gives this expression; and this figure will be certainly
that of the constituent particles of mercury. If it should appear, by
such experiments, that the attraction of mercury was in the inverse
ratio of the square of the distance, it would be clearly demonstrated
that its constituent particles were spherical, because a sphere is the
only figure which observes this law, and at whatever distance globes
are placed the law of their attraction is always the same.
Newton had some idea that chemical affinities (which are nothing more
in fact than these particular attractions which we have mentioned)
were produced by the same kind of laws as those of gravitation; but he
does not appear to have perceived that all those particular laws were
merely simple modifications of the general one, and that their apparent
difference arose solely from the circumstance of the figure of the
atoms, which attract each other, having, when at small distances, a
greater influence upon the force of this law than the mass of matter.
It is, notwithstanding, upon this theory that the perfect knowledge
of brute matter depends. The basis of all matter is the same, and
its form throughout would be perfectly similar, if the figures of
its constituent particles were not different; and thus it is that
one homogeneous substance can differ from another only in proportion
to the difference of their original particles. A body composed of
spherical particles ought to be one half specifically lighter than
that whose particles are cubical, because as the first only touch each
other by their points, they leave intermediate spaces equal to what
they occupy, whereas the cubical particles join without leaving the
smallest interval, and must consequently form a matter half as heavy
again. Although the figures are considerably varied, that variation is
by no means so great as we might imagine, since Nature has fixed the
limits of lightness and gravity. Gold and air, with respect to density,
are the two extremes, and therefore all the figures in Nature must be
comprehended as coming between those two; such as would have produced
heavier or lighter substances have been rejected.
In speaking of figures, as employed by Nature, I do not mean to imply
that they must be necessarily, or are exactly, similar to those
geometrical figures which we form in our imagination. We form laws by
supposition, and then endeavour to render them simple by abstraction.
It is very possible that there are neither exact cubes nor perfect
spheres in the universe; but as nothing certainly exists without form,
and as from the variation of substances the figures of the elements are
different, some of them most undoubtedly must approach to the sphere,
the cube, and all the other regular figures which we have conceived.
The precise, absolute, and abstract figures which our minds are so
frequently induced to admit, cannot have any existence, because all
objects are related, and differ only by almost imperceptible shades.
It is by the same rule that when I speak of one substance as being
entirely full, because composed of cubical particles, and another as
being not more than half full, because its parts are spherical, I mean
only comparatively, and not that such substances really exist; for
experience has fully informed us that in transparent bodies, such as
glass, which is both dense and heavy, there is but a small quantity of
matter in proportion to the extent of the intervals; nay, as we have
before observed, it might be demonstrated that even gold, which is the
most dense species of matter, has more vacuities than substance.
To investigate the powers of Nature is the object of rational
mechanics, while active mechanics is solely confined to a combination
of particular powers, and consequently the art of constructing
machines. This art has at all times been certain of cultivation from
necessity and convenience; and both ancients and moderns have equally
excelled in it. But rational mechanics is a science invented in our
days; for, from the days of Aristotle to those of Descartes, even the
philosophers have reasoned no better upon the nature of motion, than
uniformly to mistake the effect for the cause. Impulsion was the only
force with which they were acquainted; to it they attributed the
effects of others, and all the phenomena of the universe. If this idea
of theirs had been probable, or even possible, impulsion, which they
regarded as the sole cause, must have been a general effect, which
equally belonged to all matter, and which equally exerted itself in all
places, and at all times; but every day demonstrated the contrary to be
the fact; for they must have perceived that this force had no existence
in bodies at rest; that it had but a short subsistence in projected
bodies, being soon destroyed by resistance; that a fresh impulse was
absolutely necessary for its renewal, and that, consequently, so far
from being a general cause, it was only a particular effect produced by
others more general.
It is true, however, that we ought to consider a general effect as a
cause, for we cannot become acquainted with the real cause of this
effect, because all our knowledge is derived from comparison; and as
there is not any thing to which we can compare an effect, which is
supposed general, and equally belonging to every thing, we can know
it only by the fact. According to this view, attraction, or gravity,
being a general effect common to all matter, and clearly evinced by the
fact, ought to be considered as a cause; and to which all particular
causes should be referred, nay even that of impulsion, since it is
less general and less constant; and the principal difficulty is to
perceive how impulsion can be an effect of attraction; for if we rest
on the communication of motion by impulse, we are then persuaded that
it can only be transmitted from one body to another by elasticity, and
that all the hypotheses, which suppose a communication of motion in
hard bodies, are mere ideal fancies, which do not exist in Nature. A
perfectly hard or a perfectly elastic body is entirely imaginary, as
neither of them really exist; for it is certain that nothing exists
absolutely or in extreme; and the idea of perfection must suppose one
or the other.
It is certain that if there were no elasticity in matter there would be
no impulsive force; for instance, if we throw a stone, the motion it
acquires is communicated by the elasticity of the arm. When motion is
communicated by one body in action encountering another at rest, how
can we possibly suppose it to be done otherwise than by compressing the
spring of the elastic particles it contains, which recovering itself
almost immediately after, gives to the whole mass a force equal to
that which it received? How a perfectly hard body should admit this
force, or receive motion, is beyond comprehension; and the enquiry is
unnecessary, since no such body exists; for, all bodies are endowed
with elasticity. The force of electricity is proved by experiments to
be elastic, and to belong to matters in general; and therefore, if no
other elasticity existed in the interior parts of bodies but that of
this electrical matter, that would be sufficient for the communication
of motion; and consequently to this great spring, as a general effect,
the particular cause of impulsion must be attributed.
A little reflection on the mechanism of elasticity will convince us
that its force depends on that of attraction. To have a still more
clear idea of this subject, let us suppose a spring the most simple,
such as of a solid angle of iron, or of any other hard substance, and
then see what will be the result of compressing it. By compression
we oblige the parts adjacent to the top of the angle to bend, or to
separate a little from each other; but the pressure being removed they
again approach as near as they had done before. Their adhesion, from
which the cohesion of bodies results, is clearly an effect of their
mutual attraction. Upon the spring being pressed this adhesion is not
destroyed, because, although the particles are separated, they are not
removed beyond the sphere of their mutual attraction; consequently the
moment the pressure is taken away the force is renewed, the separated
parts draw near, and their spring is restored. But if the pressure be
too violent, they will, in that case, be removed beyond the sphere of
their attraction, and the spring will break, because the compressing
force will be greater than that of cohesion, or that of mutual
attraction, by which the particles are kept together. This proves
that elasticity can only exert itself in proportion to the cohesion
of the particles of matter, that is, in proportion as they are united
by the force of their mutual attraction; from which it results, that
elasticity in general, which alone can produce impulsion, and impulsion
itself, are owing to the force of attraction, and are only particular
effects which depend on that general one.
Notwithstanding that these ideas appear to be perfectly clear to me,
I do not expect to see them adopted. People in general reason only
from their sensations, and natural philosophers determine from their
prejudices; as, therefore, both these must be set aside, very few will
remain to form a proper judgment; but such is the dignity of Truth,
that she is content with a few admirers, and is always lost in a crowd;
she is at all times august and majestic, notwithstanding which she is
frequently obscured by fantastic opinions, and obliterated by fanciful
chimeras. I, however, view and understand Nature in this manner, and am
almost induced to believe that she is still more simple; the phenomena
exhibited by brute matter is caused by a single force, and from this
force, combined with that of heat, originate those living particles
which gave rise to, and support all, the various effects of organized
bodies.