To acquire a general or comprehensive view of this mechanism of the
globe, by which it is adapted to the purpose of being a habitable world,
it is necessary to distinguish three different bodies which compose the
whole. These are, a solid body of earth, an aqueous body of sea, and an
elastic fluid of air.

It is the proper shape and disposition of these three bodies that form
this globe into a habitable world; and it is the manner in which these
constituent bodies are adjusted to each other, and the laws of action
by which they are maintained in their proper qualities and respective
departments, that form the Theory of the machine which we are now to
examine.

Let us begin with some general sketch of the particulars now mentioned.

_1st_, There is a central body in the globe. This body supports those
parts which come to be more immediately exposed to our view, or which
may be examined by our sense and observation. This first part is
commonly supposed to be solid and inert; but such a conclusion is only
mere conjecture; and we shall afterwards find occasion, perhaps, to form
another judgment in relation to this subject, after we have examined
strictly, upon scientific principles, what appears upon the surface, and
have formed conclusions concerning that which must have been transacted
in some more central part.

_2dly_, We find a fluid body of water. This, by gravitation, is reduced
to a spherical form, and by the centrifugal force of the earth's
rotation, is become oblate. The purpose of this fluid body is essential
in the constitution of the world; for, besides affording the means of
life and motion to a multifarious race of animals, it is the source of