We thus shall find the greatest part of the calcareous masses upon this
globe to have originated from marine calcareous bodies; for whether
we examine marbles, limestones, or such solid masses as are perfectly
changed from the state of earth, and are become compact and hard, or
whether we examine the soft, earthy, chalky or marly strata, of which so
much of this earth is composed, we still find evident proofs, that those
beds had their origin from materials deposited at the bottom of the sea;
and that they have the calcareous substance which they contain, from the
same source as the marbles or the limestones.

2_dly_, In those calcareous strata, which are evidently of marine
origin, there are many parts that are of a sparry structure, that is
to say, the original texture of those beds, in such places, has been
dissolved, and a new structure has been assumed, which is peculiar to
a certain state of the calcareous earth. This change is produced by
crystallisation, in consequence of a previous state of fluidity, which
has so disposed the concreting parts, as to allow them to assume a
regular shape and structure proper to that substance. A body, whose
external form has been modified by this process, is called a _crystal_;
one whose internal arrangement of parts is determined by it, is said to
be of a _sparry structure_; and this is known from its fracture.

3_dly_, There are, in all the regions of the earth, huge masses of
calcareous matter, in that crystalline form of sparry state, in
which perhaps no vestige can be found of any organised body, nor any
indication that such calcareous matter had belonged to animals; but
as, in other masses, this sparry structure, or crystalline state, is
evidently assumed by the marine calcareous substances, in operations
which are natural to the globe, and which are necessary to the