new direction by the reins, and by his legs impels the animal in it. But, of course, the effect of the right rein is to send the haunches toward the left, so that the horse is no longer straight. Then comes the effect of the left leg to keep it straight by preventing the swing of the haunches to the left. But under the impulse of the left leg alone, the horse executes a pirouette, haunches pushed to the right by the rider's left leg, shoulders pulled to the right by the right rein.
I myself hold to a more rational theory, which differs from the principle of the old lateral equitation, and also from the reasoned equitation of Baucher and Fillis. The horse is either assembled or it is not. If it is not, go as you please. The horse makes the turn, and that is all. If the horse is assembled, the rider controls the center of gravity. This is sine qua non for the scientific equitation, which, moreover, admits at the walk and trot no other effects than the diagonal, either to obtain the equilibrium or to execute any movement. The gallop, which is the only lateral gait, requires other effects for changes of direction, of which more shortly.
When the horse is traveling straight at the walk, its feet follow the two parallel lines AC and BD, by a diagonal stride in which BC and AD support alternately the center of gravity at O. In order for the horse to turn to the right, the line CD moves to the position PL, it sends following the arcs of
