The tops of the highest mountains are generally composed of rock, stone granite, and other vitrifiable matters, which contain no shells.
All these matters were formed out of the beds of the sand of the sea, which covered the tops of these mountains. When the sea left them, the sand and other light bodies were carried by the waters into the plains, so that there remained only rocks on the tops of the mountains, which had been formed under those beds of sand. At two, three, or four hundred fathoms below the tops of these mountains, are often found marble and other calcinable matter, which are disposed in parallel strata, and contain shells and other marine productions; therefore it is not surprising that M. de la Condamine did not find any shells on these mountains, especially if he sought for them in the elevated parts of those mountains which are composed of rock, free-stone, or vitrifiable sand; but had he examined the lower parts of the Cordeliers, he would undoubtedly have found strata of stone, marble, earth, &c. mixed with shells; for in every country where observations have
been made, such beds have always been met with.
But suppose that in fact there are no marine productions in the mountains of Peru, all that may be concluded from it will no ways affect our theory; and it might be possible, that there are some parts of the globe which never were covered with water, especially of such elevation as the Cordeliers. But in this case there might be some curious observations made on those mountains, for they would not be composed of parallel strata, the materials also would be very different from those we are acquainted with; they would not have perpendicular cracks; the composition of the rocks and stones would not at all resemble those of other countries; and lastly, in these mountains we should find the ancient structure of the earth such as it originally was before it was changed by the motion of the waters; we should see the first state of the globe, the old matters of which it was composed, its form, and the natural arrangement of its parts; but this is too much to expect, and on too slight foundations; and it is more conformable to reason to conclude that fossil-shells are to be found in those mountains, as well as in every other place.
With respect to the manner in which shells are placed in the strata of earth or sand, Woodward says, "All shells that are met with in an infinity of strata of earth, and banks of rocks, in the highest mountains, and in the deepest quarries and mines, in flints, &c. &c. in masses of sulphur, marcasites, and other metallic and mineral bodies, are filled with similar substances to that which includes them, and never any heterogeneous matter, &c.
"In the sand stones of all countries (the specific weight of the different kinds of which vary but little, being generally with respect to water as 2-1/2 or 9/16 to 1), we find only the conchae, and other shells which are nearly of the same weight, but they are usually found in very great numbers, whereas it is very rare to meet with oyster-shells (whose specific weight is but as 2-1/3 to 1), or sea cockles (whose weight is but as 2 or 2-1/8 to 1), or other sorts of lighter shells; but on the contrary in chalk, (which is lighter than stone, being to water but as 2-1/10 to 1), we find only cockles and other kinds of lighter shells, page 32, 33."
It must be remarked, that what Woodward says in this place with respect to specific gravity, must not be looked upon as a general
rule, for we find lighter and heavier shells in the same matters; for example, shells of cockles, of oysters, of echini, &c. are found in the same stones and earth; and even in the royal cabinet may be seen a petrified cockle in a cornelian, and echini petrified in an agate, &c. therefore the specific weight of the shells has not influenced so much as Woodward supposes their position in the earth. The reason why such light shells are found more abundantly in chalk is, that chalk is only the ruinated part of shells, and that those of the echini being lighter and thinner than others, would have been most easily reduced into powder or chalk, so that the strata of chalk are only met with in the places where formerly a great abundance of these light shells were collected, the destruction of which formed that chalk, in which we find those shells, which having resisted the frictions, are preserved entire, or at least in parts large enough to discover their species.
But this subject is treated more fully in our discourse on minerals; we shall here content ourselves with saying, that a modification must be given to Woodward's expressions: he seems to say, that shells are found in flints, cornelians, in ores, and sulphur, as often, and in as great a
number as in other matters; whereas the truth is, that they are very rare in all vitrifiable or purely inflammable substances; and, on the contrary, are in prodigious abundance in chalk, marl, and marbles, insomuch that we cannot absolutely pretend to say, that the lightest and heaviest shells are found in corresponding strata, but only that in general they are oftener found so than otherwise. They are all filled with the substance which surrounds them, whether found in horizontal strata or in perpendicular fissures, because both have been formed by the waters, although at different times and in different manners. Those found in horizontal strata of stone, marble, &c. have been deposited by the motion of the waves of the sea, and those in flints, cornelians, and all matters which are in the perpendicular fissures, have been produced by the particular motion of a small quantity of water, loaded with lapidific or metallic substances. In both cases these matters were reduced into a fine and impalpable powder, which has filled the shells so fully and absolutely, as not to have left the least vacuum.