The seat must be understood in an extended sense as the disposition of the various parts of the body, in conformity with the action of the horse; and its effect is the rider’s being firm in the saddle, when he might be otherwise thrown forward over the horse’s head, or backward over his tail. The fundamental seat is that intermediate one of which all others are modifications, and in which the rider sits when the horse is going straight forward, without any bend in his position. In describing this, it is first necessary to consider the rider’s relation to the horse.--He must sit on that part of the animal’s body which, as he springs in his paces, is the centre of motion: from which, of course, any weight would be most difficultly shaken. The place of this seat is that part of the saddle into which the rider’s body would naturally slide were he to ride without stirrups. This seat is to be preserved only by a proper balance of his body, and its adaptation to even the most violent counteractions of the horse. Turf jockeys necessarily sit further back, that they may employ the pulls. It is necessary to consider the horseman in various parts, and to explain their different functions: 1st, the lower part, as being here the principal one, namely, the thighs, with the legs as dependent on them; 2dly, the upper part, namely, the body, with the arms dependent on it. The thighs, from the fork to the knees, are commonly called the immovable parts, and upon them the whole attitude depends. They must not wriggle or roll, so as either to disturb the horse, or render the seat loose; but they may be relaxed when the horse hesitates to advance. The legs occasionally strengthen the hold of the thighs by a grasp with the calves; and they likewise aid, support, and chastise the horse. The body, from the fork upwards, must always be in a situation to take the corresponding motion, and preserve the balance. The position of the arms is dependent on that of the body, but they also exercise new functions. As a good seat is the basis of all excellence in riding, we shall consider these parts in detail.