fore-hand than if you were placed in a
forward position. But during the time that the position is in the act of
being shifted, that is, during the time that the horse is falling, the
act of throwing your own weight back produces an exactly equivalent
pressure forward, in all respects the counterpart of your own motion
backward, in intensity and duration. It is useless to dwell on this
subject, or to adduce the familiar illustrations which it admits of. It
is a simple proposition of mechanical equilibrium, and any one who is
conversant with such subjects _must_ assent to it.

[Sidenote: Mechanical assistance of jockey.]

The question whether a jockey can mechanically assist his horse, does
not rest on the same footing. I believe he can, thus. If a man sits
astride of a chair, with his feet off the ground, and clasps the chair
with his legs, by the muscular exertion of his lower limbs he can jump
the chair along. The muscular force is there employed on the foreign
fulcrum, the ground, through the medium of the legs of the chair. The
muscular action strikes the chair downward and backward, and if the
chair was on ice it would recede, so also would the feet of a horse in
attempting to strike forward. If the chair was on soft ground, it would
sink, so also would a horse, in proportion to the force of the muscular
stroke. But if the resistance of the ground is complete, the reaction,
which is precisely equal and in a contrary direction to the action, will
throw the body of the man upward and forward, and by clasping with his
legs he will draw the chair also with him. But he can only accomplish in
this way a very little distance with a very great exertion. If the
jockey made this muscular exertion every time that his horse struck with
his hind feet, his strength would be employed on the foreign fulcrum,
the ground, through the medium of his horse's bony frame. Thus the
jockey would contribute to the horizontal impulse of his own weight, and
exactly in proportion to the muscular power exerted by the jockey, the
muscular system of the horse would be relieved. At the same time no
additional task is thrown on the bony frame of the horse, since, if the
jockey had not used his muscular power on it in impelling his own
weight, the muscular system of the horse must have been so employed. It
is true, that not much is done after all with a prodigious exertion, but
if that little gains six inches in a hardly contested race it may make
t