HORSE-BACK RIDING. 27 



horse throws himself forward on two feet placed 

 diagonally he imparts to the rider an impulse which 

 will be suddenly arrested when he comes down upon 

 the other two. It is this sudden stop which causes 

 the shock, the rebound which we all feel when trot- 

 ting on horseback, however gentle it may be, and 

 which is repeated at every step. 



The direction of the movement which is communi- 

 cated to us is the result of several forces. 



First. It is proved that when two bodies move 

 forward, one upon the other, the upper one always 

 inclines to go beyond the perpendicular line. 



Secondly. The forward movement of the horse 

 takes the rider with it, and urges him in the same 

 direction. 



Thirdly. The shock is received at the point of sup- 

 port, while the weight in consequence of the velocity 

 acquired acts always upon the upper portions of the 

 body, and causes them to continue the forward 

 movement. 



Fourthly. In the act of leaping, the horse raises the 

 body upward as well as forward, and the weight 

 which causes It to fall again when the horse marks 

 the second measure, that is, makes the second move- 

 ment, still more increases the severity of the reac- 

 tion. The result of all three forces combined is to 

 urge the rider forward on the line of a slight curve. 



In galloping, however, the movement is much 

 more simple. It consists almost v/holly of a series of 



