bodies, tend to fall with the same
velocity, and, in fact, all do; for though, for the reason just stated,
a feather will take longer to reach the ground than an ounce of lead, an
ounce of lead will fall as fast as a hundredweight. And that it is the
resistance of the air, and not any diminution in the power of
attraction, which causes the feather to lag behind, may be proved by
experiment; for if you let a feather and a coin drop together from the
top of the exhausted receiver of an air-pump, they will both be seen to
descend at the same rate, and reach the bottom at the same instant; a
fact which may be demonstrated more simply by placing the coin and
feather free of each other in a paper cone, and letting the cone fall
with its apex downwards, so as to break the air's resistance; or by
suspending a piece of gold-leaf in a bottle, and letting the bottle
drop--of course short of the ground--in which case the included leaf
will be seen to have gone as fast and as far as the bottle.

It is to be especially noticed that attraction is no lopsided affair;
that it is mutual; that, while the larger body attracts the less, the
less also attracts and moves the larger in proportion; and that, indeed,
every body and every particle attracts every other, far as well as near,
to the utmost verge of the universe of matter. Under it the moon
maintains its place with reference to the earth, the planets with
reference to the sun, and the solar system with reference to the
stellar. As for the moon, it maintains its orbit and revolves round the
earth under the action of two forces, the one akin to that by which a
ball is projected from the mouth of a cannon, and the other the
attraction of the earth, which, by its constant and equal operation,
bends its otherwise rectilineal track into a circular one, as we might
show if we could only project a ball with such a force as exactly to
balance the power of gravity, so that it would at no point in its course
be drawn nearer the earth than at starting.

That the force we are considering pervades the solar system is
demonstrable, for it is on the supposition of it and the laws it is
known to obey that all the calculations of astronomy--and they never
miscarry--are grounded; and it is by noticing disturbances in the
otherwise regular movements of certain planets that astronomers have
been led more than once to infer and discover the presence of some
hitherto unknown body in the neighbourhood. It