formed by the sediment of the sea, often extend to considerable
distances, and we often find in hills, separated by a valley, the same
beds and the same matters at the same level. This observation agrees
perfectly with that of the height of the opposite hills. We may easily
be assured of the truth of these facts, for in all narrow vallies, where
rocks are discovered, we shall find the same beds of stone and marble on
both sides at the same height. In a country where I frequently reside, I
found a quarry of marble which extended more than 12 leagues in length,
and whose breadth was very considerable, although I have never been able
precisely to determine it. I have often observed that this bed of marble
is throughout of the same thickness, and in hills divided from this
quarry by a valley of 100 feet depth, and a quarter of a mile in
breadth, I found the same bed of marble at the same height. I am
persuaded it is the same in every stone and marble quarry where shells
are found; but this observation does not hold good in quarries of
freestone. In the course of this work, we shall give reasons for this
difference, and describe why freestone is not dispersed, like other
matters, in horizontal beds, and why it is in irregular blocks, both in
form and position.
We have likewise observed that the strata are the same on both sides the
straits of the sea. This observation, which is important, may lead us to
discover the lands and islands which have been separated from the
continent; it proves, for example, that England has been divided from
France; Spain from Africa; Sicily from Italy; and it is to be wished
that the same observation had been made in all the straits. I am
persuaded that we should find it almost every where true. We do not know
whether the same beds of stone are found at the same height on both
sides the straits of Magellan, which is the longest; but we see, by the
particular maps and exact charts, that the two high coasts which confine
it, form nearly, like the mountains of the earth, correspondent angles,
which also proves that the Terra del Fuega, must be regarded as part of
the continent of America; it is the same with Forbisher's Strait and
the island of Friesland, which appear to have been divided from the
continent of Greenland.
The Maldivian islands are only separated by small tracts of the sea, on
each side of which banks and rocks are found composed of the same
materials; and these islands, which, taken together, are near 200 miles
long, formed anciently only one land; they are now divided into 13
provinces, called Clusters. Each cluster contains a great number of
small islands, most of which are sometimes overflowed and sometimes dry;
but what is remarkable, these thirteen clusters are each surrounded with
a chain of rocks of the same stone, and there are only three or four
dangerous inlets by which they can be entered. They are all placed one
after the other, and it evidently appears that these islands were
formerly a long mountain capped with rocks[216:A].
Many authors, as Verstegan, Twine, Somner, and especially Campbell, in
his Description of England, in the chapter of Kent, gives very strong
reasons, to prove that England was formerly joined to France, and has
been separated from it by an effort of the sea, which carried away the
neck of land that joined them, opened the channel, and left naked a
great quantity of low and marshy ground along the southern coasts of
England. Dr. Wallis, as a corroboration of this supposition, shews the
conformity of the ancient Gallic and British tongues, and adds many
observations, which we shall relate in the following articles.
If we consider the form of lands, the position of mountains, and the
windings of rivers, we shall perceive that generally opposite hills are
not only composed of the same matters on the same level, but are nearly
of an equal height. This equality I have observed in my travels, and
have mostly found them the same on the two sides, especially in vallies
that were not more than a quarter or a third of a league broad, for in
vallies which are very broad, it is difficult to judge of the height and
equality of hills, because, by looking over a level plain of any great
extent, it appears to rise, and hills at a distance appear to lower; but
this is not the place to give a mathematical reason for this difference.
It is also very difficult to judge by the naked sight of the middle of a
great valley, at least if there is no river in it; whereas in confined
vallies our sight is less equivocal and our judgment more certain. That
part of Burgundy comprehended between Auxerre, Dijon, Autun, and
Bar-sur-seine, a considerable extent of which is called _la Bailliage de
la Montagne_, is one of the highest parts of France; from one side of
most of these mountains, which are only of the second class, the water
flows towards the Ocean, and on the other side towards the
Mediterranean. This high country is divided with many small vallies,
very confined, and almost all watered with rivulets. I have a thousand
times observed the correspondence of the angles of these hills and their
equality of height, and I am certain that I have every where found the
saliant angles opposite to the returning angles, and the heights nearly
equal on both sides. The farther we advance into the higher country,
where the points of division are, the higher are the mountains; but this
height is always the same on both sides of the vallies, and the hills
are raised or lowered alike. I have frequently made the like
observations in many other parts of France. It is this equality in the
height of the hills which forms the plains in the mountains, and these
plains form lands higher than others. But high mountains do not appear
so equal in height, most of them terminate in points and irregular
peaks; and I have seen, in crossing the Alps, and the Apennine
mountains, that the angles are, in fact, correspondent; but it is almost
impossible to judge by the eye of the equality or inequality in the
height of opposite mountains, because their summits are lost in mists
and clouds.
The different strata of which the earth is composed are not disposed
according to their specific weight, for we often find strata of heavy
matters placed on those of lighter. To be assured of this, we have only
to examine the earth on which rocks are placed, and we shall find that
it is generally clay or sand, which is specifically lighter. In hills,
and other small elevations, we easily discover this to be the case; but
it is not so with large mountains, for not only their summits are rocks,
but those rocks are placed on others; there mountains are placed upon
mountains, and rocks upon rocks, to such a considerable height, and
through so great an extent of country, that we can scarcely be certain
whether there is earth at bottom, or of what nature it is. I have seen
cavities made in rocks to some hundred feet deep, without being able to
form an idea where they ended, for these rocks were supported by
others; nevertheless, may we not compare great with small? and since
the rocks of little mountains, whose bases are to be seen, rest on the
earth less heavy and solid than stone, may we not suppose that earth is
also the base of high mountains? All that I have here to prove by these
arguments is, that, by the motion of the waters, it may naturally happen
that the more ponderous matters accumulated on the lighter; and that, if
this in fact is found to be so in most hills, it is probable that it
happened as explained by my theory; but should it be objected that I am
not grounded in supposing, that before the formation of mountains the
heaviest matters were below the lighter; I answer, that I assert nothing
general in this respect, because this effect may have been produced in
many manners, whether the heaviest matters were uppermost or undermost,
or placed indiscriminately. To conceive how the sea at first formed a
mountain of clay, and afterwards capt it with rocks, it is sufficient to
consider the sediments may successively come from different parts, and
that they might be of different materials. In some parts, the sea may at
first have deposited sediments of clay, and the waters afterwards
brought sediment of strong matter, either because they had transported
all the clay from the bottom and sides, and then the waves attacked the
rocks, possibly because the first sediment came from one part, and the
second from another. This perfectly agrees with observation, by which we
perceive that beds of earth, stone, gravel, sand, &c. followed no rule
in their arrangement, but are placed indifferently one on the other as
it were by chance.
But this chance must have some rules, which can be known only by
estimating the value of probabilities, and the truth of conjectures.
According to our hypothesis, on the formation of the globe, we have seen
that the interior part of the globe must have been a vitrified matter,
similar to vitrified sand, which is only the fragments of glass, and of
which the clays are perhaps the scoria; by this supposition, the centre
of the earth, and almost as far as the external circumference, must be
glass, or a vitrified matter; and above this we shall find sand, clay,
and other scoria. Thus the earth, in its first state, was a nucleus of
glass, or vitrified matter; either massive like glass, or divided like
sand, because that depends on the degree of heat it has undergone. Above
this matter was sand, and lastly clay. The soil of the waters and air
produced the external crust, which is thicker or thinner, according to
the situation of the ground; more or less coloured, according to the
different mixtures of mud, sand, clay, and the decayed parts of animals
and vegetables; and more or less fertile, according to the abundance or
want of these parts. To shew that this supposition on the formation of
sand and clay is not chimerical, I shall add some particular remarks.
I conceive, that the earth, in its first state, was a globe, or rather a
spheroid of compact glass, covered with a light crust of pumice stone
and other scoria of the matter in fusion. The motion and agitation of
the waters and air soon reduced this crust into powder or sand, which,
by uniting afterwards, produced flints, and owe their hardness, colour,
or transparency and variety, to the different degrees of purity of the
sand which entered into their composition.
These sands, whose constituting parts unite by fire, assimilate, and
become very dense, compact, and the more transparent as the sand is more
pure; on the contrary, being exposed a long time to the air, they
disunite and exfoliate, descend in the form of earth, and it is
probable the different clays are thus produced. This dust, sometimes of
a brightish yellow, and sometimes like silver, is nothing else but a
very pure sand somewhat perished, and almost reduced to an elementary
state. By time, particles will be so far attenuated and divided, that
they will no longer have power to reflect the light, and acquire all the
properties of clay.
This theory is conformable to what every day is seen; let us immediately
wash sand upon its being dug, and the water will be loaded with a black
ductile and fat earth, which is genuine clay. In streets paved with
freestone, the dirt is always black and greasy, and when dried appears
to be an earth of the same nature as clay. Let us wash the earth taken
from a spot where there are neither freestone nor flints, and there will
always precipitate a great quantity of vitrifiable sand.
But what perfectly proves that sand, and even flint and glass, exist in
clay, is, that the action of fire, by uniting the parts, restores it to
its original form. Clay, if heated to the degree of calcination, will
cover itself with a very hard enamel; if it is not vitrified internally,
it nevertheless will have acquired a very great hardness, so as to
resist the file; it will emit fire under the hammer, and it has all the
properties of flint; a greater degree of heat causes it to flow, and
converts it into real glass.
Clay and sand are therefore matters perfectly analogous, and of the same
class; if clay, by condensing, may become flint and glass, why may not
sand, by dissolution, become clay? Glass appears to be true elementary
earth, and all mixed substances disguised glass. Metals, minerals,
salts, &c. are only vitrifiable earth; common stone and other matters
analogous to it, and testaceous and crustaceous shells, &c. are the only
substances which cannot be vitrified, and which seem to form a separate
class. Fire, by uniting the divided parts of the first, forms an
homogeneous matter, hard and transparent, without any diminution of
weight, and to which it is not possible to cause any alteration; those,
on the contrary, in which a greater quantity of active and volatile
principles enter, and which calcine, lose more than one-third of their
weight in the fire, and retake the form of simple earth, without any
other alteration than a disunion of their different parts: these bodies
excepted, which are no great number, and whose combinations produce no
great varieties in nature, every other substance, and particularly
clay, may be converted into glass, and are consequently only decomposed
glass. If the fire suddenly causes the form of these substances to
change, by vitrifying them, glass itself, whether pure, or in the form
of sand or flint, naturally, but by a slow and insensible progress,
changes into clay.
Where flint is the predominant stone, the country is generally strewed
with parts of it, and if the place is uncultivated, and these stones
have been long exposed to the air, without having been stirred, their
upper superficies is always white, whereas the opposite side, which
touches the earth, is very brown, and preserves its natural colour. If
these flints are broken, we shall perceive that the whiteness is not
only external, but penetrates internally, and there forms a kind of
band, not very deep in some, but which in others occupies almost the
whole flint. This white part is somewhat grainy, entirely opaque, as
soft as freestone, and adheres to the tongue like the boles; whereas the
other part is smooth, has neither thread nor grain, and preserves its
natural colour, transparency, and hardness. If this flint is put into a
furnace, its white part becomes of a brick colour, and its brown part
of a very fine white. Let us not say with one of our most celebrated
naturalists, that these stones are imperfect flints of different ages,
which have not acquired their perfection; for why should they be all
imperfect? Why should they be imperfect only on the side exposed to the
weather? It, on the contrary, appears to me more reasonable that they
are flints changed from their original state, gradually decomposed, and
assuming the form and property of clay or bole. If this is thought to be
only conjecture, let the hardest and blackest flint be exposed to the
weather, in less than a year its surface will change colour; and if we
have patience to pursue this experiment, we shall see it by degrees lose
its hardness, transparency, and other specific characters, and approach
every day nearer and nearer the nature of clay.
What happens to flint happens to sand; each grain of sand may possibly
be considered as a small flint, and each flint as a mass of extremely
fine grains of sand. The first example of the decomposition of sand is
found in the brilliant opaque powder called Mica, in which clay and
slate are always diffused. The entirely transparent flints, the Quartz,
produce, by decomposition, fat and soft talks, such as those of Venice
and Russia, which are as ductile and vitrifiable as clay: and it appears
to me, that talk is a mediate between glass, or transparent flint, and
clay; whereas coarse and impure flint, by decomposing, passes to clay
without any intermedium.
Our factitious glass undergoes the same alterations: it decomposes and
perishes, as it were, in the air. At first, it assumes a variety of
colours, then exfoliates, and by working it, we perceive brilliant
scales fall off; but when its decomposition is more advanced, it
crumbles between the fingers, and is reduced into a very white fine
talky powder. Art has even imitated nature in the decomposition of glass
and flint. "Est etiam certa methodus solius aquæ communis ope, silices &
arenam in liquorem viscosum, eumdemque in sal viride convertendi, & hoc
in aleum rubicundum, &c. Solius ignis & aqua ope, speciali experimento,
durissimos quosque lapides in mucorem resolvo, qui distillan subtilem
spiritum exhibet & oleum nullus laudibus prœdicabile[218:A]."
These matters more particularly belong to metals, and when we come to
them, shall be fully treated on, therefore we shall content ourselves
here with adding, that the different strata which cover the terrestrial
globe, being materials to be considered as actual vitrifications or
analogous to glass, and possessing its most essential qualities; and as
it is evident, that from the decomposition of glass and flint, which is
every day made before our eyes, a genuine clay remains, it is not a
precarious supposition to advance, that clays and sands have been formed
by scoria, and vitrified drops of the terrestrial globe, especially when
we join the proofs _a priori_, which we have given to evince the earth
has been in a state of liquefaction caused by fire.
FOOTNOTES:
[198:A] Essay on the Natural History of the Earth, pages 40, 41, 42, &c.
[199:A] See Varennii, Geograph. General, page 46.
[205:A] See the Mem. of the Acad. 1716, page 14.
[216:A] See the Voyages of Francis Piriard, vol. 1, page 108.
[218:A] See Becher. Phys. subter.
ARTICLE VIII.
ON SHELLS, AND OTHER MARINE PRODUCTIONS FOUND IN THE INTERIOR PARTS OF
THE EARTH.
I have often examined quarries, the banks of which were filled with
shells; I have seen entire hills composed of them, and chains of rocks
which contained them throughout their whole extent. The quantity of
these marine productions is astonishing, and the number in many places
so prodigious, that it appears scarcely possible that any should now
remain in the sea; it is by considering this innumerable multitude of
shells, that no doubt is left of our earth having been a long time under
the water of the ocean. The quantity found in a fossil, or petrified
state, is beyond conception, and it is only from the number of those
that have been discovered that we could possibly have formed an idea of
their multiplicity. We must imagine, like those who reason on matters
they never saw, that shells are only found at random, dispersed here and
there, or in small heaps, as oyster shells thrown before our doors; on
the contrary, they form mountains, are met with in shoals of 100 or 200
miles length, nay, they may sometimes be traced through whole provinces
in masses of 50 or 60 feet thick. It is from these circumstances alone
that we can reason on the subject.
We cannot give a more striking example on this subject than the shells
of Touraine. The following is the description given of them by the
historian of the Academy[220:A].
"The number of figured stones and fossil shells found in the bowels of
the earth were remarked in all ages and nations, but they were
considered merely as the sports of nature, and even by philosophers
themselves, as the productions of chance or accident; they regarded them
with a degree of surprise, but passed them over with a slight attention,
and all this phenomena perished without any fruit for the progress of
knowledge. A potter in Paris, who knew neither Latin nor Greek, towards
the end of the 16th century, was the first man who dared affirm, in
opposition to the learned, that the fossil shells were real shells
formerly deposited by the sea in those places where they were found;
that animals, and particularly fish, had given to stones all these
different figures, &c. and he desired the whole school of Aristotle to
contradict his proofs. This was Bernard Palissy, as great a natural
genius as nature could form: his system slept near 100 years, and even
his name was almost forgot. At length the ideas of Palissy were revived
in the mind of several philosophers; and science has profited by all the
shells and figured stones the earth furnishes us with; perhaps they are
at present become only too common, and the consequences drawn from them
too incontestable.
"Notwithstanding this, the observations presented by M. Reaumer must
appear wonderful. He discovered a mass of 130 million, 680 thousand
cubical fathoms of shells, either whole or in fragments, without any
mixture of stone, earth, sand, or other extraneous matter: hitherto
fossil shells have never appeared in such an enormous quantity, nor
without mixture. It is in Touraine this prodigious mass is found, more
than 36 leagues from the sea; this is perfectly known there, as the
farmers of that province make use of these shells, which they dig up, as
manure for their lands, to fertilize their plains, which otherwise would
be absolutely sterile.
"What is dug from the earth, and which generally is no more than eight
or nine feet deep, are only small fragments of shells, very
distinguishable as fragments, for they retain their original channels
and hollows, having only lost their gloss and colour, as almost all
shells do which we find in the earth. The smallest pieces, which are
only dust, are still distinguishable because they are perfectly of the
same matter as the rest, as well as of the whole shells which are
sometimes found. We discover the species as well in the whole shells as
in the larger fragments. Some of these species are known at Poictou,
others belong to more remote coasts. There are even fragments of
madrepores, coral, and other productions of the sea; all this matter in
the country is termed _Fallun_, and is found wherever the ground is dug
in that province for the space of nine leagues square. The peasants do
not dig above twenty feet deep, because they think it would not repay
them for their trouble, but they are certainly deeper. The calculation
of the quantity is however taken upon the supposition of only 18 feet
and 2200 fathoms to the league. This mass of shells of course exceeds
the calculation, and possibly contains double the quantity.
"In physical points the smallest circumstances, which most people do not
think worthy of remarking, sometimes lead to consequences and afford
great lights. M. de Reaumer observed, that all these fragments of shells
lie horizontally, and hence he has concluded that this infinity of
fragments does not proceed from the heap being formed at one time, or of
whole shells, for the uppermost, by their weight, would have crushed
the others, and of course their fallings would have given an infinity of
different positions. They must, therefore, have been brought there by
the sea, either whole or broken, and necessarily placed horizontal; and
although the extreme length of time was of itself sufficient to break,
and almost calcine the greatest part, it could not change their
position.
"By this it appears, that they must have been brought gradually, and, in
fact, how was it possible that the sea could convey at once such an
immense quantity of shells, and at the same time preserve a position
perfectly horizontal? they must have collected in one spot, and
consequently this spot must have been the bottom of a gulph or basin.
"All this proves, that although there must remain upon the earth many
vestiges of the universal deluge, as recorded in scripture, the mass of
shells at Touraine was not produced by that deluge; there is perhaps not
so great a mass in any part of the sea; but even had the deluge forced
them away, it would have been with an impetuosity and violence that
would not have permitted them to retain one uniform position. They must
have been brought and deposited gently and slowly, and consequently
their accumulation required a space of time much longer than a year."