those parts which are immediately conducive to action; if his
shoulders incline well backwards, his legs and joints in
proportion, his carcase strong and deep, his thighs well let down,
we shall find he may be a very good racer, even when tried by the
principles of mechanics, without appealing to his blood for any
part of his goodness. We are taught by this doctrine of mechanics,
that the power applied to any body, must be adequate to the weight
of that body, otherwise, such power will be deficient for the
action we require; and there is no man but knows a cable or chord
of three inches diameter is not equal in strength to a chord of
four inches diameter. So that if it should be asked why a handsome
coach Horse, with as much beauty, length, and proportion as a
foreign Horse, will not act with the same velocity and
perseverance, nothing will be more easily answered, without
appealing to blood; because we shall find the powers of acting in
a foreign Horse much more prevalent, and more equal to the weight
of his body, than the powers of acting in a coach Horse: for
whoever has been curious enough to examine the mechanism of
different Horses by dissection, will find the tendon of the leg in
a foreign Hose is much larger than in any other Horse, whose leg
is of the same dimensions; and as the external texture of a
foreign Horse is much finer than of any other, so the foreign
Horse must necessarily have the greatest strength and perseverance
in acting, because the muscular power of two Horses (whose
dimensions are the same) will be the greatest in that Horse, whose
texture is the finest.

Let us next inquire what information we can gather from the
science of Anatomy, concerning the laws of motion: it teaches us,
that the force and power of a muscle consists in the number of