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 fibres of which it is composed; and that the velocity and motion of a muscle consists in the length and extent of its fibres. Let us compare this doctrine with the language of the jockey: he tells us, if a Horse has not length, he will be slow; and if made to slender, he will not be able to bring his weight through. Does not the observation of the jockey exactly correspond with this doctrine? If we now inquire into the motion of Horses, we shall find the bones are the levers of the body, and the tendons and muscles (which are one and the same thing) are the powers of acting applied to these levers. Now when we consider a half-bred Horse running one mile or more, with the same velocity as a Horse of foreign extraction, we do not impute that equality of velocity to any innate quality in the half-bred Horse, because we can account for it by external causes: that is by an equality of the length, and extent of his levers and tendons. And when we consider a half-bred Horse running one mile, or more, with the same velocity as the other, and then giving it up, what shall we do? shall we say the foreigner beats him by his blood, or by the force and power of his tendons? or can we, without reproaching our own reason and understanding, impute that to be the effect of occult and hidden causes in the one of these instances and not in the other? both of which are demonstrated with certainty, and reduced