Vestiges of the Natural History of Creation (Chapter 2)
by Robert Chambers
CONSTITUENT MATERIALS OF THE EARTH
AND OF THE OTHER BODIES OF SPACE.
he 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
ingradients, 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 liquidds; 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 1,180,682 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.
It is unavoidably held as a strong proof in favour of
any hypothesis, when all the relative phenomena are in harmony with it.
This is eminently the case with the nebulous hypothesis, for here the
associated facts cannot be explained on any other supposition. We have seen
reason to conclude that the primary condition of matter was that of a
diffused mass, in which the component molecules were probably kept apart
through the efficacy of heat; that portions of this agglomerated into suns,
which threw off planets; that these planets were at first very much
diffused, but gradually contracted by cooling to their present dimensions.
Now, as to our own globe, there is a remarkable proof of its having been in
a fluid state at the time when it was finally solidifying, in the fact of
its being bulged at the equator, the very form which a soft revolving body
takes, and must inevitably take, under the influence of centrifugal force.
This bulging makes the equatorial exceed the polar diameter as 230 to 229,
which has been demonstrated to be precisely the departure from a correct
sphere which might be predicated from a knowledge of the amount of the mass
and the rate of rotation. There is an almost equally distinct memorial of
the original high temperature of the materials, in the store of heat which
still exists in the interior. The immediate surface of the earth, be it
observed, exhibits only the temperature which might be expected to be
imparted to such materials, by the heat of the sun. There is a point, very
short way down, but varying in different climes, where all effect from the
sun's rays ceases. Then, however, commences a temperature from an entirely
different cause, one which evidently has its source in the interior of the
earth, and which regularly increases as we descend to greater and greater
depths, the rate of increment being about one degree Fahrenheit for every
sixty feet; and of this high temperature there are other evidences, in the
phenomena of volcanoes and thermal springs, as well as in what is
ascertained with regard to the density of the entire mass of the earth.
This, it will be remembered, is four and a half times the weight of water;
but the actual weight of the principal solid substances composing the outer
crust is as two and a half times the weight of water; and this, we know,
if the globe were solid and cold, should increase vastly towards the
centre, water acquiring the density of quicksilver at 362 miles below the
surface, and other things in proportion, and these densities becoming much
greater at greater depths; so that the entire mass of a cool globe should
be of a gravity infinitely exceeding four and a half times the weight of
water. The only alternative supposition is, that the central materials are
greatly expanded or diffused by some means; and by what means could they be
so expanded but by heat? Indeed, the existence of this central heat, a
residuum of that which kept all matter in a vaporiform chaos at first, is
amongst the most solid discoveries of modern
science,[1] and the support which it gives to
Herschel's explanation of the formation of worlds is most important. We
shall hereafter see what appear to be traces of an operation of this heat
upon the surface of the earth in very remote times; an effect, however,
which has long passed entirely away. The central heat has, for ages,
reached a fixed point, at which it will probably remain for ever, as the
non-conducting quality of the cool crust absolutely prevents it from
suffering any diminution.
Notes
The researches on this subject were conducted
chiefly by the late Baron Fourier, perpetual secretary to the Academy of
Sciences of Paris. See his Théorie Analytique de la Chaleur.
1822.
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[ Robert Chambers,
Vestiges of the
Natural History of Creation, 1st edition, 1844; Reprinted in James Secord,
ed., Chicago: University of Chicago Press, 1994, pp. 27-43. ]
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