If I might now be allowed to give my opinion of this propriety of length, I should say it consisted in the depth and declivity of the shoulders, and in the length of the quarters and thighs, and the insertion of the muscles thereof.  The effect of the different position or attitude of the shoulders in all Horses, is very demonstrable:  if we consider the motion of a shoulder, we shall find it limited to a certain degree by the ligamentous and the tendinous parts, which confine it to its proper sphere of acting; so that if the shoulder stand upright, the Horse will not be able to put his toes far before him, but will acquire only such a particular degree of space at each step or movement; but if the shoulders have a declivity in them, he cannot only put his toes farther before him, but a greater purchase of ground will be obtained at every stroke.

The certainty of this effect in the declivity of the shoulders will be known by every man’s observation; and it is also easily demonstrated by the principles of mechanics, by which we learn, that if a weight is applied to a pulley, in order to shut a door, and that weight be allowed to fall immediately and perpendicularly from the door, it will not pull it too with that velocity as it will do if an angle be acquired, and the weight pass over a wheel removed to a very little distance from the door.

Nevertheless, there is no general rule without exception, for we now and then find a Horse to be a good racer, who has not this declivity in his shoulders, but from a length in his thighs and quarters has a sufficient share of speed.  Add to this, there is another advantage obtained to the Horse besides velocity by this declivity of the shoulders, for his weight is removed farther back, and placed more in the center of his body, by which an equilibrium is acquired, and every muscle bears a more equal share of weight and action; so that the nearer the articulation of the quarters approach to the superior part of the shoulders, so much the shorter will the back be, and as much more expanded as the chest is, so much stronger will the animal be, and will also have a larger space for the organs of respiration to exert themselves.

But I would not be understood to mean, that the shortness of the back, or capacity of the chest, will constitute a racer; far from it:  but that in any given and proportioned length, from the bosom of the Horse to the settting on of the dock, the nearer the superior points of the shoulders approach to the quarters, so much better able will the carcase be to sustain and bring through the weight; and as much as the shoulders themselves prevail in depth, and the quarters and thighs in length, so much greater will be the velocity of the Horse, because a greater purchase of ground is hereby obtained at every stroke.

It is by this proprity of length, strength of carcase, and the power of the muscles, that foreign Horse excel all others, and it is by the same advantages they excel each other also, and not by any innate virtue, or principle of the mind, which must be understood by the word blood, if any thing at all is intended to be understood by it; and this is a truth every man would be convinced of, if he would divest himself of partiality to particular blood, and confide in his own observation of Horses and their performances.