Transcribed from the 1844 John Churchill edition by David Price, email
ccx074@pglaf.org
VESTIGES
OF
THE NATURAL HISTORY
OF
CREATION.
* * * * *
LONDON:
JOHN CHURCHILL, PRINCES STREET, SOHO.
M DCCC XLIV.
CONTENTS.
PAGE
The Bodies of Space—Their arrangements and formation 1
Constituent materials of the Earth and of the other Bodies 27
of Space
The Earth formed—Era of the Primary Rocks 44
Commencement of Organic Life—Sea Plants, Corals, etc. 54
Era of the Old Red Sandstone—Fishes abundant. 66
Secondary Rocks. Era of the Carboniferous Formation.—Land 76
formed—Commencement of Land Plants
Era of the New Red Sandstone—Terrestrial Zoology commences 94
with Reptiles—First traces of Birds
Era of the Oolite—Commencement of Mammalia 105
Era of the Cretaceous Formation 116
Era of the Tertiary Formation—Mammalia abundant 125
Era of the Superficial Formations—Commencement of present 134
Species
General Considerations respecting the Origin of the 145
Animated Tribes
Particular Considerations respecting the Origin of the 165
Animated Tribes
Hypothesis of the Development of the Vegetable and Animal 191
Kingdoms
Macleay System of Animated Nature—This System considered in 236
connexion with the Progress of Organic Creation, and as
indicating the natural status of Man
Early History of Mankind 277
Mental Constitution of Animals 324
Purpose and General Condition of the Animated Creation 361
Note Conclusory 387
THE BODIES OF SPACE,
THEIR ARRANGEMENTS AND FORMATION.
IT is familiar knowledge that the earth which we inhabit is a globe of
somewhat less than 8000 miles in diameter, being one of a series of
eleven which revolve at different distances around the sun, and some of
which have satellites in like manner revolving around them. The sun,
planets, and satellites, with the less intelligible orbs termed comets,
are comprehensively called the solar system, and if we take as the
uttermost bounds of this system the orbit of Uranus (though the comets
actually have a wider range), we shall find that it occupies a portion of
space not less than three thousand six hundred millions of miles in
extent. The mind fails to form an exact notion of a portion of space so
immense; but some faint idea of it may be obtained from the fact, that,
if the swiftest race-horse ever known had begun to traverse it, at full
speed, at the time of the birth of Moses, he would only as yet have
accomplished half his journey.
It has long been concluded amongst astronomers, that the stars, though
they only appear to our eyes as brilliant points, are all to be
considered as suns, representing so many solar systems, each bearing a
general resemblance to our own. The stars have a brilliancy and apparent
magnitude which we may safely presume to be in proportion to their actual
size and the distance at which they are placed from us. Attempts have
been made to ascertain the distance of some of the stars by calculations
founded on parallax, it being previously understood that, if a parallax
of so much as one second, or the 3600th of a degree, could be ascertained
in any one instance, the distance might be assumed in that instance as
not less than 19,200 millions of miles! In the case of the most
brilliant star, Sirius, even this minute parallax could not be found;
from which of course it was to be inferred that the distance of that star
is something beyond the vast distance which has been stated. In some
others, on which the experiment has been tried, no sensible parallax
could be detected; from which the same inference was to be made in their
case. But a sensible parallax of about one second has been ascertained
in the case of the double star, α α, of the constellation of the Centaur,
{3} and one of the third of that amount for the double star, 61 Cygni;
which gave reason to presume that the distance of the former might be
about twenty thousand millions of miles, and the latter of much greater
amount. If we suppose that similar intervals exist between all the
stars, we shall readily see that the space occupied by even the
comparatively small number visible to the naked eye, must be vast beyond
all powers of conception.
The number visible to the eye is about three thousand; but when a
telescope of small power is directed to the heavens, a great number more
come into view, and the number is ever increased in proportion to the
increased power of the instrument. In one place, where they are more
thickly sown than elsewhere, Sir William Herschel reckoned that fifty
thousand passed over a field of view two degrees in breadth in a single
hour. It was first surmised by the ancient philosopher, Democritus, that
the faintly white zone which spans the sky under the name of the Milky
Way, might be only a dense collection of stars too remote to be
distinguished. This conjecture has been verified by the instruments of
modern astronomers, and some speculations of a most remarkable kind have
been formed in connexion with it. By the joint labours of the two
Herschels, the sky has been “gauged” in all directions by the telescope,
so as to ascertain the conditions of different parts with respect to the
frequency of the stars. The result has been a conviction that, as the
planets are parts of solar systems, so are solar systems parts of what
may be called astral systems—that is, systems composed of a multitude of
stars, bearing a certain relation to each other. The astral system to
which we belong, is conceived to be of an oblong, flattish form, with a
space wholly or comparatively vacant in the centre, while the extremity
in one direction parts into two. The stars are most thickly sown in the
outer parts of this vast ring, and these constitute the Milky Way. Our
sun is believed to be placed in the southern portion of the ring, near
its inner edge, so that we are presented with many more stars, and see
the Milky Way much more clearly, in that direction, than towards the
north, in which line our eye has to traverse the vacant central space.
Nor is this all. Sir William Herschel, so early as 1783, detected a
motion in our solar system with respect to the stars, and announced that
it was tending towards the star λ, in the constellation Hercules. This
has been generally verified by recent and more exact calculations, {5}
which fix on a point in Hercules, near the star 143 of the 17th hour,
according to Piozzi’s catalogue, as that towards which our sun is
proceeding. It is, therefore, receding from the inner edge of the ring.
Motions of this kind, through such vast regions of space, must be long in
producing any change sensible to the inhabitants of our planet, and it is
not easy to grasp their general character; but grounds have nevertheless
been found for supposing that not only our sun, but the other suns of the
system pursue a wavy course round the ring _from west to east_, crossing
and recrossing the middle of the annular circle. “Some stars will depart
more, others less, from either side of the circumference of equilibrium,
according to the places in which they are situated, and according to the
direction and the velocity with which they are put in motion. Our sun is
probably one of those which depart furthest from it, and descend furthest
into the empty space within the ring.” {6} According to this view, a
time may come when we shall be much more in the thick of the stars of our
astral system than we are now, and have of course much more brilliant
nocturnal skies; but it may be countless ages before the eyes which are
to see this added resplendence shall exist.
The evidence of the existence of other astral systems besides our own is
much more decided than might be expected, when we consider that the
nearest of them must needs be placed at a mighty interval beyond our own.
The elder Herschel, directing his wonderful tube towards the _sides_ of
our system, where stars are planted most rarely, and raising the powers
of the instrument to the required pitch, was enabled with awe-struck mind
to see suspended in the vast empyrean astral systems, or, as he called
them, firmaments, resembling our own. Like light cloudlets to a certain
power of the telescope, they resolved themselves, under a greater power,
into stars, though these generally seemed no larger than the finest
particles of diamond dust. The general forms of these systems are
various; but one at least has been detected as bearing a striking
resemblance to the supposed form of our own. The distances are also
various, as proved by the different degrees of telescopic power necessary
to bring them into view. The farthest observed by the astronomer were
estimated by him as thirty-five thousand times more remote than Sirius,
supposing its distance to be about twenty thousand millions of miles. It
would thus appear, that not only does gravitation keep our earth in its
place in the solar system, and the solar system in its place in our
astral system, but it also may be presumed to have the mightier duty of
preserving a local arrangement between that astral system and an
immensity of others, through which the imagination is left to wander on
and on without limit or stay, save that which is given by its inability
to grasp the unbounded.
The two Herschels have in succession made some other most remarkable
observations on the regions of space. They have found within the limits
of our astral system, and generally in its outer fields, a great number
of objects which, from their foggy appearance, are called _nebulæ_; some
of vast extent and irregular figure, as that in the sword of Orion, which
is visible to the naked eye; others of shape more defined; others, again,
in which small bright nuclei appear here and there over the surface.
Between this last form and another class of objects, which appear as
clusters of nuclei with nebulous matter around each nucleus, there is but
a step in what appears a chain of related things. Then, again, our
astral space shews what are called nebulous stars,—namely, luminous
spherical objects, bright in the centre and dull towards the extremities.
These appear to be only an advanced condition of the class of objects
above described. Finally, nebulous stars exist in every stage of
concentration, down to that state in which we see only a common star with
a slight _bur_ around it. It may be presumed that all these are but
stages in a progress, just as if, seeing a child, a boy, a youth, a
middle-aged, and an old man together, we might presume that the whole
were only variations of one being. Are we to suppose that we have got a
glimpse of the process through which a sun goes between its original
condition, as a mass of diffused nebulous matter, and its full-formed
state as a compact body? We shall see how far such an idea is supported
by other things known with regard to the occupants of space, and the laws
of matter.
A superficial view of the astronomy of the solar system gives us only the
idea of a vast luminous body (the sun) in the centre, and a few smaller,
though various sized bodies, revolving at different distances around it;
some of these, again, having smaller planets (satellites) revolving
around them. There are, however, some general features of the solar
system, which, when a profounder attention makes us acquainted with them,
strike the mind very forcibly.
It is, in the first place, remarkable, that the planets all move nearly
_in one plane_, corresponding with the centre of the sun’s body. Next,
it is not less remarkable that the motion of the sun on its axis, those
of the planets around the sun, and the satellites around their primaries,
{9} and the motions of all on their axes, are _in one direction_—namely,
from west to east. Had all these matters been left to accident, the
chances against the uniformity which we find would have been, though
calculable, inconceivably great. Laplace states them at four millions of
millions to one. It is thus powerfully impressed on us, that the
uniformity of the motions, as well as their general adjustment to one
plane, must have been a consequence of some cause acting throughout the
whole system.
Some of the other relations of the bodies are not less remarkable. The
primary planets shew a progressive increase of bulk and diminution of
density, from the one nearest to the sun to that which is most distant.
With respect to density alone, we find, taking water as a measure and
counting it as one, that Saturn is 13/32, or less than half; Jupiter, 1
1/24; Mars, 3 2/7; Earth, 4 1/2; Venus, 5 11/15; Mercury 9 9/10, or about
the weight of lead. Then the distances are curiously relative. It has
been found that if we place the following line of numbers,—
0 3 6 12 24 48 96 192,
and add 4 to each, we shall have a series denoting the respective
distances of the planets from the sun. It will stand thus—
4 7 10 16 28 52 100 196
Merc. Venus. Earth. Mars. Jupiter. Saturn. Uranus.
It will be observed that the first row of figures goes on from the second
on the left hand in a succession of duplications, or multiplications by
2. Surely there is here a most surprising proof of the unity which I am
claiming for the solar system. It was remarked when this curious
relation was first detected, that there was a want of a planet
corresponding to 28; the difficulty was afterwards considered as in a
great measure overcome, by the discovery of four small planets revolving
at nearly one mean distance from the sun, between Mars and Jupiter. The
distances bear an equally interesting mathematical relation to the times
of the revolutions round the sun. It has been found that, with respect
to any two planets, the squares of the times of revolution are to each
other in the same proportion as the cubes of their mean distances,—a most
surprising result, for the discovery of which the world was indebted to
the illustrious Kepler. Sir John Herschel truly observes—“When we
contemplate the constituents of the planetary system from the point of
view which this relation affords us, it is no longer mere analogy which
strikes us, no longer a general resemblance among them, as individuals
independent of each other, and circulating about the sun, each according
to its own peculiar nature, and connected with it by its own peculiar
tie. The resemblance is now perceived to be a true _family likeness_;
they are bound up in one chain—interwoven in one web of mutual relation
and harmonious agreement, subjected to one pervading influence which
extends from the centre to the farthest limits of that great system, of
which all of them, the Earth included, must henceforth be regarded as
members.” {12}
Connecting what has been observed of the series of nebulous stars with
this wonderful relationship seen to exist among the constituents of our
system, and further taking advantage of the light afforded by the
ascertained laws of matter, modern astronomers have suggested the
following hypothesis of the formation of that system.
Of nebulous matter in its original state we know too little to enable us
to suggest how nuclei should be established in it. But, supposing that,
from a peculiarity in its constitution, nuclei are formed, we know very
well how, by virtue of the law of gravitation, the process of an
aggregation of the neighbouring matter to those nuclei should proceed,
until masses more or less solid should become detached from the rest. It
is a well-known law in physics that, when fluid matter collects towards
or meets in a centre, it establishes a rotatory motion. See minor
results of this law in the whirlwind and the whirlpool—nay, on so humble
a scale as the water sinking through the aperture of a funnel. It thus
becomes certain that when we arrive at the stage of a nebulous star, we
have a rotation on an axis commenced.
Now, mechanical philosophy informs us that, the instant a mass begins to
rotate, there is generated a tendency to fling off its outer portions—in
other words, the law of centrifugal force begins to operate. There are,
then, two forces acting in opposition to each other, the one attracting
_to_, the other throwing _from_, the centre. While these remain exactly
counterpoised, the mass necessarily continues entire; but the least
excess of the centrifugal over the attractive force would be attended
with the effect of separating the mass and its outer parts. These outer
parts would, then, be left as a ring round the central body, which ring
would continue to revolve with the velocity possessed by the central mass
at the moment of separation, but not necessarily participating in any
changes afterwards undergone by that body. This is a process which might
be repeated as soon as a new excess arose in the centrifugal over the
attractive forces working in the parent mass. It might, indeed, continue
to be repeated, until the mass attained the ultimate limits of the
condensation which its constitution imposed upon it. From what cause
might arise the periodical occurrence of an excess of the centrifugal
force? If we suppose the agglomeration of a nebulous mass to be a
process attended by refrigeration or cooling, which many facts render
likely, we can easily understand why the outer parts, hardening under
this process, might, by virtue of the greater solidity thence acquired,
begin to present some resistance to the attractive force. As the
solidification proceeded, this resistance would become greater, though
there would still be a tendency to adhere. Meanwhile, the condensation
of the central mass would be going on, tending to produce a separation
from what may now be termed the _solidifying crust_. During the
contention between the attractions of these two bodies, or parts of one
body, there would probably be a ring of attenuation between the mass and
its crust. At length, when the central mass had reached a certain stage
in its advance towards solidification, a separation would take place, and
the crust would become a detached ring. It is clear, of course, that
some law presiding over the refrigeration of heated gaseous bodies would
determine the stages at which rings were thus formed and detached. We do
not know any such law, but what we have seen assures us it is one
observing and reducible to mathematical formulæ.
If these rings consisted of matter nearly uniform throughout, they would
probably continue each in its original form; but there are many chances
against their being uniform in constitution. The unavoidable effects of
irregularity in their constitution would be to cause them to gather
towards centres of superior solidity, by which the annular form would, of
course, be destroyed. The ring would, in short, break into several
masses, the largest of which would be likely to attract the lesser into
itself. The whole mass would then necessarily settle into a spherical
form by virtue of the law of gravitation; in short, would then become a
planet revolving round the sun. Its rotatory motion would, of course,
continue, and satellites might then be thrown off in turn from its body
in exactly the same way as the primary planets had been thrown off from
the sun. The rule, if I can be allowed so to call it, receives a
striking support from what appear to be its exceptions. While there are
many chances against the matter of the rings being sufficiently equable
to remain in the annular form till they were consolidated, it might
nevertheless be otherwise in some instances; that is to say, the
equableness might, in those instances, be sufficiently great. Such was
probably the case with the two rings around the body of Saturn, which
remain a living picture of the arrangement, if not the condition, in
which all the planetary masses at one time stood. It may also be
admitted that, when a ring broke up, it was possible that the fragments
might spherify separately. Such seems to be the actual history of the
ring between Jupiter and Mars, in whose place we now find four planets
much beneath the smallest of the rest in size, and moving nearly at the
same distance from the sun, though in orbits so elliptical, and of such
different planes, that they keep apart.
It has been seen that there are mathematical proportions in the relative
distances and revolutions of the planets of our system. It has also been
suggested that the periods in the condensation of the nebulous mass, at
which rings were disengaged, must have depended on some particular crises
in the condition of that mass, in connexion with the laws of centrifugal
force and attraction. M. Compte, of Paris, has made some approach to the
verification of the hypothesis, by calculating what ought to have been
the rotation of the solar mass at the successive times when its surface
extended to the various planetary orbits. He ascertained that _that
rotation corresponded in every case with the actual sidereal revolution
of the planets_, _and that the rotation of the primary planets in like
manner corresponded with the orbitual periods of the secondaries_. The
process by which he arrived at this conclusion is not to be readily
comprehended by the unlearned; but those who are otherwise, allow that it
is a powerful support to the present hypothesis of the formation of the
globes of space. {17}
The nebular hypothesis, as it has been called, obtains a remarkable
support in what would at first seem to militate against it—the existence
in our firmament of several thousands of solar systems, in which there
are more than one sun. These are called double and triple stars. Some
double stars, upon which careful observations have been made, are found
to have a regular revolutionary motion round each other in ellipses.
This kind of solar system has also been observed in what appears to be
its rudimental state, for there are examples of nebulous stars containing
two and three nuclei in near association. At a certain point in the
confluence of the matter of these nebulous stars, they would all become
involved in a common revolutionary motion, linked inextricably with each
other, though it might be at sufficient distances to allow of each
distinct centre having afterwards its attendant planets. We have seen
that the law which causes rotation in the single solar masses, is exactly
the same which produces the familiar phenomenon of a small whirlpool or
dimple in the surface of a stream. Such dimples are not always single.
Upon the face of a river where there are various contending currents, it
may often be observed that two or more dimples are formed near each other
with more or less regularity. These fantastic eddies, which the musing
poet will sometimes watch abstractedly for an hour, little thinking of
the law which produces and connects them, are an illustration of the
wonders of binary and ternary solar systems.
The nebular hypothesis is, indeed, supported by so many ascertained
features of the celestial scenery, and by so many calculations of exact
science, that it is impossible for a candid mind to refrain from giving
it a cordial reception, if not to repose full reliance upon it, even
without seeking for it support of any other kind. Some other support I
trust yet to bring to it; but in the meantime, assuming its truth, let us
see what idea it gives of the constitution of what we term the universe,
of the development of its various parts, and of its original condition.
Reverting to a former illustration—if we could suppose a number of
persons of various ages presented to the inspection of an intelligent
being newly introduced into the world, we cannot doubt that he would soon
become convinced that men had once been boys, that boys had once been
infants, and, finally, that all had been brought into the world in
exactly the same circumstances. Precisely thus, seeing in our astral
system many thousands of worlds in all stages of formation, from the most
rudimental to that immediately preceding the present condition of those
we deem perfect, it is unavoidable to conclude that all the perfect have
gone through the various stages which we see in the rudimental. This
leads us at once to the conclusion that the whole of our firmament was at
one time a diffused mass of nebulous matter, extending through the space
which it still occupies. So also, of course, must have been the other
astral systems. Indeed, we must presume the whole to have been
originally in one connected mass, the astral systems being only the first
division into parts, and solar systems the second.
The first idea which all this impresses upon us is, that the formation of
bodies in space is _still and at present in progress_. We live at a time
when many have been formed, and many are still forming. Our own solar
system is to be regarded as completed, supposing its perfection to
consist in the formation of a series of planets, for there are
mathematical reasons for concluding that Mercury is the nearest planet to
the sun, which can, according to the laws of the system, exist. But
there are other solar systems within our astral system, which are as yet
in a less advanced state, and even some quantities of nebulous matter
which have scarcely begun to advance towards the stellar form. On the
other hand, there are vast numbers of stars which have all the appearance
of being fully formed systems, if we are to judge from the complete and
definite appearance which they present to our vision through the
telescope. We have no means of judging of the seniority of systems; but
it is reasonable to suppose that, among the many, some are older than
ours. There is, indeed, one piece of evidence for the probability of the
comparative youth of our system, altogether apart from human traditions
and the geognostic appearances of the surface of our planet. This
consists in a thin nebulous matter, which is diffused around the sun to
nearly the orbit of Mercury, of a very oblately spheroidal shape. This
matter, which sometimes appears to our naked eyes, at sunset, in the form
of a cone projecting upwards in the line of the sun’s path, and which
bears the name of the Zodiacal Light, has been thought a residuum or last
remnant of the concentrating matter of our system, and thus may be
supposed to indicate the comparative recentness of the principal events
of our cosmogony. Supposing the surmise and inference to be correct, and
they may be held as so far supported by more familiar evidence, we might
with the more confidence speak of our system as not amongst the elder
born of Heaven, but one whose various phenomena, physical and moral, as
yet lay undeveloped, while myriads of others were fully fashioned and in
complete arrangement. Thus, in the sublime chronology to which we are
directing our inquiries, we first find ourselves called upon to consider
the globe which we inhabit as a child of the sun, elder than Venus and
her younger brother Mercury, but posterior in date of birth to Mars,
Jupiter, Saturn, and Uranus; next to regard our whole system as probably
of recent formation in comparison with many of the stars of our
firmament. We must, however, be on our guard against supposing the earth
as a recent globe in our ordinary conceptions of time. From evidence
afterwards to be adduced, it will be seen that it cannot be presumed to
be less than many hundreds of centuries old. How much older Uranus may
be no one can tell, much less how more aged may be many of the stars of
our firmament, or the stars of other firmaments than ours.
Another and more important consideration arises from the hypothesis;
namely, as to the means by which the grand process is conducted. The
nebulous matter collects around nuclei by virtue of the law of
attraction. The agglomeration brings into operation another physical
law, by force of which the separate masses of matter are either made to
rotate singly, or, in addition to that single motion, are set into a
coupled revolution in ellipses. Next centrifugal force comes into play,
flinging off portions of the rotating masses, which become spheres by
virtue of the same law of attraction, and are held in orbits of
revolution round the central body by means of a composition between the
centrifugal and gravitating forces. All, we see, is done by certain laws
of matter, so that it becomes a question of extreme interest, what are
such laws? All that can yet be said, in answer, is, that we see certain
natural events proceeding in an invariable order under certain
conditions, and thence infer the existence of some fundamental
arrangement which, for the bringing about of these events, has a force
and certainty of action similar to, but more precise and unerring than
those arrangements which human society makes for its own benefit, and
calls laws. It is remarkable of physical laws, that we see them
operating on every kind of scale as to magnitude, with the same
regularity and perseverance. The tear that falls from childhood’s cheek
is globular, through the efficacy of that same law of mutual attraction
of particles which made the sun and planets round. The rapidity of
Mercury is quicker than that of Saturn, for the same reason that, when we
wheel a ball round by a string and make the string wind up round our
fingers, the ball always flies quicker and quicker as the string is
shortened. Two eddies in a stream, as has been stated, fall into a
mutual revolution at the distance of a couple of inches, through the same
cause which makes a pair of suns link in mutual revolution at the
distance of millions of miles. There is, we might say, a sublime
simplicity in this indifference of the grand regulations to the vastness
or minuteness of the field of their operation. Their being uniform, too,
throughout space, as far as we can scan it, and their being so unfailing
in their tendency to operate, so that only the proper conditions are
presented, afford to our minds matter for the gravest consideration. Nor
should it escape our careful notice that the regulations on which all the
laws of matter operate, are established on a rigidly accurate
mathematical basis. Proportions of numbers and geometrical figures rest
at the bottom of the whole. All these considerations, when the mind is
thoroughly prepared for them, tend to raise our ideas with respect to the
character of physical laws, even though we do not go a single step
further in the investigation. But it is impossible for an intelligent
mind to stop there. We advance from law to the cause of law, and ask,
What is that? Whence have come all these beautiful regulations? Here
science leaves us, but only to conclude, from other grounds, that there
is a First Cause to which all others are secondary and ministrative, a
primitive almighty will, of which these laws are merely the mandates.
That great Being, who shall say where is his dwelling-place, or what his
history! Man pauses breathless at the contemplation of a subject so much
above his finite faculties, and only can wonder and adore!
CONSTITUENT MATERIALS OF THE EARTH
AND OF THE OTHER BODIES OF SPACE.
THE nebular hypothesis almost necessarily supposes matter to have
originally formed one mass. We have seen that the same physical laws
preside over the whole. Are we also to presume that the constitution of
the whole was uniform?—that is to say, that the whole consisted of
similar elements. It seems difficult to avoid coming to this conclusion,
at least under the qualification that, possibly, various bodies, under
peculiar circumstances attending their formation, may contain elements
which are wanting, and lack some which are present in others, or that
some may entirely consist of elements in which others are entirely
deficient.
What are elements? This is a term applied by the chemist to a certain
limited number of substances, (fifty-four or fifty-five are ascertained,)
which, in their combinations, form all the matters of every kind present
in and about our globe. They are called elements, or simple substances,
because it has hitherto been found impossible to reduce them into others,
wherefore they are presumed to be the primary bases of all matters. It
has, indeed, been surmised that these so-called elements are only
modifications of a primordial form of matter, brought about under certain
conditions; but if this should prove to be the case, it would little
affect the view which we are taking of cosmical arrangements. Analogy
would lead us to conclude that the combinations of the primordial matter,
forming our so-called elements, are as universal or as liable to take
place everywhere as are the laws of gravitation and centrifugal force.
We must therefore presume that the gases, the metals, the earths, and
other simple substances, (besides whatever more of which we have no
acquaintance,) exist or are liable to come into existence under proper
conditions, as well in the astral system, which is thirty-five thousand
times more distant than Sirius, as within the bounds of our own solar
system or our own globe.
Matter, whether it consist of about fifty-five ingredients, or only one,
is liable to infinite varieties of condition under different
circumstances, or, to speak more philosophically, under different laws.
As a familiar illustration, water, when subjected to a temperature under
32° Fahrenheit, becomes ice; raise the temperature to 212°, and it
becomes steam, occupying a vast deal more space than it formerly did.
The gases, when subjected to pressure, become liquids; for example,
carbonic acid gas, when subjected to a weight equal to a column of water
1230 feet high, at a temperature of 32°, takes this form: the other gases
require various amounts of pressure for this transformation, but all
appear to be liable to it when the pressure proper in each case is
administered. Heat is a power greatly concerned in regulating the volume
and other conditions of matter. A chemist can reckon with considerable
precision what additional amount of heat would be required to vaporise
all the water of our globe; how much more to disengage the oxygen which
is diffused in nearly a proportion of one-half throughout its solids;
and, finally, how much more would be required to cause the whole to
become vaporiform, which we may consider as equivalent to its being
restored to its original nebulous state. He can calculate with equal
certainty what would be the effect of a considerable diminution of the
earth’s temperature—what changes would take place in each of its
component substances, and how much the whole would shrink in bulk.
The earth and all its various substances have at present a certain volume
in consequence of the temperature which actually exists. When, then, we
find that its matter and that of the associate planets was at one time
diffused throughout the whole space, now circumscribed by the orbit of
Uranus, we cannot doubt, after what we know of the power of heat, that
the nebulous form of matter was attended by the condition of a very high
temperature. The nebulous matter of space, previously to the formation
of stellar and planetary bodies, must have been a universal Fire Mist, an
idea which we can scarcely comprehend, though the reasons for arriving at
it seem irresistible. The formation of systems out of this matter
implies a change of some kind with regard to the condition of the heat.
Had this power continued to act with its full original repulsive energy,
the process of agglomeration by attraction could not have gone on. We do
not know enough of the laws of heat to enable us to surmise how the
necessary change in this respect was brought about, but we can trace some
of the steps and consequences of the process. Uranus would be formed at
the time when the heat of our system’s matter was at the greatest, Saturn
at the next, and so on. Now this tallies perfectly with the exceeding
diffuseness of the matter of those elder planets, Saturn being not more
dense or heavy than the substance cork. It may be that a sufficiency of
heat still remains in those planets to make up for their distance from
the sun, and the consequent smallness of the heat which they derive from
his rays. And it may equally be, since Mercury is twice the density of
the earth, that its matter exists under a degree of cold for which that
planet’s large enjoyment of the sun’s rays is no more than a
compensation. Thus there may be upon the whole a nearly equal experience
of heat amongst all these children of the sun. Where, meanwhile, is the
heat once diffused through the system over and above what remains in the
planets? May we not rationally presume it to have gone to constitute
that luminous envelope of the sun, in which his warmth-giving power is
now held to reside? It could not be destroyed—it cannot be supposed to
have gone off into space—it must have simply been reserved to constitute,
at the last, a means of sustaining the many operations of which the
planets were destined to be the theatre.
The tendency of the whole of the preceding considerations is to bring the
conviction that our globe is a specimen of all the similarly-placed
bodies of space, as respects its constituent matter and the physical and
chemical laws governing it, with only this qualification, that there are
_possibly_ shades of variation with respect to the component materials,
and _undoubtedly_ with respect to the conditions under which the laws
operate, and consequently the effects which they produce. Thus, there
may be substances here which are not in some other bodies, and substances
here solid may be elsewhere liquid or vaporiform. We are the more
entitled to draw such conclusions, seeing that there is nothing at all
singular or special in the astronomical situation of the earth. It takes
its place third in a series of planets, which series is only one of
numberless other systems forming one group. It is strikingly—if I may
use such an expression—a member of a democracy. Hence, we cannot suppose
that there is any peculiarity about it which does not probably attach to
multitudes of other bodies—in fact, to all that are analogous to it in
respect of cosmical arrangements.
It therefore becomes a point of great interest—what are the materials of
this specimen? What is the constitutional character of this object,
which may be said to be a sample, presented to our immediate observation,
of those crowds of worlds which seem to us as the particles of the desert
sand-cloud in number, and to whose profusion there are no conceivable
local limits?
The solids, liquids, and aeriform fluids of our globe are all, as has
been stated, reducible into fifty-five substances hitherto called
elementary. Six are gases; oxygen, hydrogen, and nitrogen being the
chief. Forty-two are metals, of which eleven are remarkable as
composing, in combination with oxygen, certain earths, as magnesia, lime,
alumin. The remaining six, including carbon, silicon, sulphur, have not
any general appellation.
The gas oxygen is considered as by far the most abundant substance in our
globe. It constitutes a fifth part of our atmosphere, a third part of
water, and a large proportion of every kind of rock in the crust of the
earth. Hydrogen, which forms two-thirds of water, and enters into some
mineral substances, is perhaps next. Nitrogen, of which the atmosphere
is four-fifths composed, must be considered as an abundant substance.
The metal silicium, which unites with oxygen in nearly equal parts to
form silica, the basis of nearly a half of the rocks in the earth’s
crust, is, of course, an important ingredient. Aluminium, the metallic
basis of alumin, a large material in many rocks, is another abundant
elementary substance. So, also, is carbon a small ingredient in the
atmosphere, but the chief constituent of animal and vegetable substances,
and of all fossils which ever were in the latter condition, amongst which
coal takes a conspicuous place. The familiarly-known metals, as iron,
tin, lead, silver, gold, are elements of comparatively small magnitude in
that exterior part of the earth’s body which we are able to investigate.
It is remarkable of the simple substances that they are generally in some
compound form. Thus, oxygen and nitrogen, though in union they form the
aerial envelope of the globe, are never found separate in nature. Carbon
is pure only in the diamond. And the metallic bases of the earths,
though the chemist can disengage them, may well be supposed unlikely to
remain long uncombined, seeing that contact with moisture makes them
burn. Combination and re-combination are principles largely pervading
nature. There are few rocks, for example, that are not composed of at
least two varieties of matter, each of which is again a compound of
elementary substances. What is still more wonderful with respect to this
principle of combination, all the elementary substances observe certain
mathematical proportions in their unions. One volume of them unites with
one, two, three, or more volumes of another, any extra quantity being
sure to be left over, if such there should be. It is hence supposed that
matter is composed of infinitely minute particles or atoms, each of which
belonging to any one substance, can only (through the operation of some
as yet hidden law) associate with a certain number of the atoms of any
other. There are also strange predilections amongst substances for each
other’s company. One will remain combined in solution with another, till
a third is added, when it will abandon the former and attach itself to
the latter. A fourth being added, the third will perhaps leave the
first, and join the new comer.
Such is an outline of the information which chemistry gives us regarding
the constituent materials of our globe. How infinitely is the knowledge
increased in interest, when we consider the probability of such being the
materials of the whole of the bodies of space, and the laws under which
these everywhere combine, subject only to local and accidental
variations!
In considering the cosmogenic arrangements of our globe, our attention is
called in a special degree to the moon.
In the nebular hypothesis, satellites are considered as masses thrown off
from their primaries, exactly as the primaries had previously been from
the sun. The orbit of any satellite is also to be regarded as marking
the bounds of the mass of the primary at the time when that satellite was
thrown off; its speed likewise denotes the rapidity of the rotatory
motion of the primary at that particular juncture. For example, the
outermost of the four satellites of Jupiter revolves round his body at
the distance of 1,180,582 miles, shewing that the planet was once
3,675,501 miles in circumference, instead of being, as now, only 89,170
miles in diameter. This large mass took rather more than sixteen days
six hours and a half (the present revolutionary period of the outermost
satellite) to rotate on its axis. The innermost satellite must have been
formed when the planet was reduced to a circumference of 309,075 miles,
and rotated in about forty-two hours and a half.
From similar inferences, we find that the mass of the earth, at a certain
point of time after it was thrown off from the sun, was no less than
482,000 miles in diameter, being sixty times what it has since shrunk to.
At that time, the mass must have taken rather more than twenty-nine and a
half days to rotate, (being the revolutionary period of the moon,)
instead of as now, rather less than twenty-four hours.
The time intervening between the formation of the moon and the earth’s
diminution to its present size, was probably one of those vast sums in
which astronomy deals so largely, but which the mind altogether fails to
grasp.
The observations made upon the surface of the moon by telescopes, tend
strongly to support the hypothesis as to all the bodies of space being
composed of similar matters, subject to certain variations. It does not
appear that our satellite is provided with that gaseous envelope which,
on earth, performs so many important functions. Neither is there any
appearance of water upon the surface; yet that surface is, like that of
our globe, marked by inequalities and the appearance of volcanic
operations. These inequalities and volcanic operations are upon a scale
far greater than any which now exist upon the earth’s surface. Although,
from the greater force of gravitation upon its exterior, the mountains,
other circumstances being equal, might have been expected to be much
smaller than ours, they are, in many instances, equal in height to nearly
the highest of our Andes. They are generally of extreme steepness, and
sharp of outline, a peculiarity which might be looked for in a planet
deficient in water and atmosphere, seeing that these are the agents which
wear down ruggedness on the surface of our earth. The volcanic
operations are on a stupendous scale. They are the cause of the bright
spots of the moon, while the want of them is what distinguishes the
duller portions, usually but erroneously called _seas_. In some parts,
bright volcanic matter, besides covering one large patch, radiates out in
long streams, which appear studded with subordinate _foci_ of the same
kind of energy. Other objects of a most remarkable character are ring
mountains, mounts like those of the craters of earthly volcanoes,
surrounded immediately by vast and profound circular pits, hollowed under
the general surface, these again being surrounded by a circular wall of
mountain, rising far above the central one, and in the inside of which
are terraces about the same height as the inner eminence. The well-known
bright spot in the south-east quarter, called by astronomers _Tycho_, and
which can be readily distinguished by the naked eye, is one of these
ring-mountains. There is one of 200 miles in diameter, with a pit 22,000
feet deep; that is, twice the height of Ætna. It is remarkable, that the
maps given by Humboldt of a volcanic district in South America, and one
illustrative of the formerly volcanic district of Auvergne, in France,
present features strikingly like many parts of the moon’s surface, as
seen through a good glass.
These characteristics of the moon forbid the idea that it can be at
present a theatre of life like the earth, and almost seem to declare that
it never can become so. But we must not rashly draw any such
conclusions. The moon may be only in an earlier stage of the progress
through which the earth has already gone. The elements which seem
wanting may be only in combinations different in those which exist here,
and may yet be developed as we here find them. Seas may yet fill the
profound hollows of the surface; an atmosphere may spread over the whole.
Should these events take place, meteorological phenomena, and all the
phenomena of organic life, will commence, and the moon, like the earth,
will become a green and inhabited world.