quantity of matter of the body acted upon is equal to the velocity
multiplied into the quantity of matter of the acting body.

The primary motions of matter may be divided into three classes, those
belonging to gravitation, to chemistry, and to life; and each class has its
peculiar laws. Though these three classes include the motions of solid,
liquid, and aerial bodies; there is nevertheless a fourth division of
motions; I mean those of the supposed ethereal fluids of magnetism,
electricity, heat, and light; whose properties are not so well investigated
as to be classed with sufficient accuracy.

_1st._ The gravitating motions include the annual and diurnal rotation of
the earth and planets, the flux and reflux of the ocean, the descent of
heavy bodies, and other phænomena of gravitation. The unparalleled sagacity
of the great NEWTON has deduced the laws of this class of motions from the
simple principle of the general attraction of matter. These motions are
distinguished by their tendency to or from the centers of the sun or
planets.

_2d._ The chemical class of motions includes all the various appearances of
chemistry. Many of the facts, which belong to these branches of science,
are nicely ascertained, and elegantly classed; but their laws have not yet
been developed from such simple principles as those above-mentioned; though
it is probable, that they depend on the specific attractions belonging to
the particles of bodies, or to the difference of the quantity of attraction
belonging to the sides and angles of those particles. The chemical motions
are distinguished by their being generally attended with an evident
decomposition or new combination of the active materials.

_3d._ The third class includes all the motions of the animal and vegetable