e principally bones, and even
entire skeletons, which, after having been stripped of the skin
and flesh that covered them, have remained, some buried in the
earth, others hidden in deep caverns. They are, sometimes,
calcined in whole or in part, without having lost their
configuration; they at others preserve, not only their texture,
but even some traces of their hair and skin. They are also
occasionally seen covered with a calcareous crust.

"Petrifactions, to use this word in its familiar sense, include
all stony bodies that have the figure of an organized body.
There are cases in which a strong solution has penetrated into
a cavity formed by an organic body that has disappeared. Then
the strong substance has occupied the cavity that has been left
empty, and has taken the external form of the body that
formerly existed there. If this body were, for instance, a
branch or trunk of a tree, the stone will have at its surface
its knots and asperities; but within, it will present all the
characters of a true stone; it will be no more, to use the
language of Hauy, than the statue of the substance that it has
replaced.

"At other times, a vegetable or animal substance, while
undergoing decomposition in a successive manner, and by obvious
degrees, is pressed by the petrifying liquid that already
surrounds it. As soon as an organic particle has disappeared,
its place is occupied by one of stone."

* * * * *

"Metallized bodies, and those which have been changed into
bitumen or carbon, belong to this system of formation; thus,
the turquoises, for instance, are the teeth of a great marine
animal; a metallic substance has penetrated them, and has
gradually replaced the softer parts of the bones.

"Impressions are often found between the plates of slaty rocks;
they are relievos or intaglios representing the skeletons of
animals, particularly fish, leaves, seeds, and entire plants,
of which the most common kind belong to the forus."

The impressions of vegetables are most abundant in the shales that
accompany coal formations; those of leaves and branches are the most
common, but there are a few instances in which they retain the delicate
structure of the flowers. All analogy leads to the inference, that those
now found in temperate