urb will indeed give the horse so much pain in the
mouth that he will throw his head up, and this so flatters the hand that
its prowess has saved him, that the rider exclaims "It may be
impossible, but it happens every day. Shall I not believe my own
senses?" The answer is, No, not if it can be explained how the senses
are deceived. Otherwise, we should still believe, as, till some few
centuries ago, the world did believe, that the diurnal motion was in the
sun, and not in the earth. Otherwise we must subscribe to the philosophy
of the Turk, who

"Saw with his own eyes the moon was round,
Was also certain that the earth was square,
Because he'd journey'd fifty miles and found
No sign of its being circular anywhere."

[Sidenote: Harm is done by the attempt.]

But these errors are not harmless errors. They induce an ambitious
interference with the horse at the moment in which he should be left
unconfined to the use of his own energies. If by pulling, and giving
him pain in the mouth, you force him to throw up his head and neck, you
prevent his seeing how to foot out any unsafe ground, or where to take
off at a fence, and in the case of stumbling you prevent an action
practically dictated by nature and theoretically justified by
philosophy. When an unmounted horse stumbles, nature teaches him to drop
his head and neck; philosophy teaches us the reason of it. During the
instant that his head and neck are dropping the shoulders are relieved
from their weight, and that is the instant in which the horse makes his
effort to recover himself. If by giving him pain in his mouth, you force
him to raise his head and neck instead of sinking them, his shoulders
will still remain encumbered with the weight of them; more than this, as
action and reaction are equal and in contrary directions, the muscular
power employed to raise the head and neck will act to sink the shoulders
and knees. The mechanical impossibility of the rider assisting his horse
when falling may be demonstrated thus: no motion can be given to a body
without a foreign force or a foreign fulcrum. Your strength is not a
foreign force, since it is employed entirely on the horse. Nor can it be
employed on the foreign fulcrum, the ground, through the medium of your
reins; as much as you pull up, so much you pull down. If a man in a boat
uses an oar, he can accelerate or impede the motion of the boat, because
his strength is employed through the medium