ce and are supported
by it, how many are the causes, as proved by history and the
sciences, of epochs after epochs of revolutions, which have more or
less completely destroyed them.

"How many are the causes by which man loses all trace of that which
has existed, and cannot believe nor even conceive of the immense
antiquity of the earth he inhabits!

"How great will yet seem this antiquity of the terrestrial globe in
the eyes of man when he shall form a just idea of the origin of
living bodies, as also of the causes of the development and of the
gradual process of perfection of the organization of these bodies,
and especially when it will be conceived that, time and favorable
circumstances having been necessary to give existence to all the
living species such as we actually see, he is himself the last
result and the actual maximum of this process of perfecting, the
limit (_terme_) of which, if it exists, cannot be known."

In the fourth chapter of the book there is less to interest the reader,
since the author mainly devotes it to a reiteration of the ideas of his
earlier works on physics and chemistry. He claims that the minerals and
rocks composing the earth's crust are all of organic origin, including
even granite. The thickness of this crust he thinks, in the absence of
positive knowledge, to be from three to four leagues, or from nine to
twelve miles.

After describing the mode of formation of minerals, including agates,
flint, geodes, etc., he discusses the process of fossilization by
molecular changes, silicious particles replacing the vegetable or animal
matter, as in the case of fossil wood.

While, then, the products of animals such as corals and molluscs are
limestones, those of vegetables are humus and clay; and all of these
deposits losing their less fixed principles pass into a silicious
condition, and end by being reduced to quartz, which is the earthy
element in its purest form. The salts, pyrites, and metals only differ
from other minerals by the different circumstances under which they were
accumulated, in their different proportions, and in their much greater
amount of carbonic or acidific fire.

Regarding granite, which, he says, naturalists very erroneously consider
as _primitive_, he begins by observing that it is only by conjecture
that we should designate as primitive any matter whatever. He recognizes
the fact that granite forms the highest mountains, which a