148 



ANIMAL MECHANISM. 



By turning an adjusting screw we fix it to the horse-shoe 



by three catches, which 

 keep the instrument se- 

 curely fastened. A strong 

 band of india-rubber passes 

 over the apparatus (fig. 42), 

 and keeps in its place the 

 ball filled with horse-hair, 

 so as to allow it to rise 

 slightly above the lower 

 surface of the hoof. When 

 the foot strikes the ground, 

 the india-rubber ball is 

 compressed, and drives a 

 part of the confined air 

 into the registering instru- 

 ments. When the foot is 

 raised, the ball recovers its 

 form, and draws again into 

 its interior the air which 



Fig. 42.— Experimental apparatus to show the pressure had expelled. 



ground''''''^ ^''''^ '''' ^^'^ These instruments soon 



wear out on the road, but 

 will last during some time on the artificial soil of the riding- 

 school. 



For experiments which we have made on ordinary roads, 

 we have had recourse to an instrument represented in fig. 43. 



To the leg of the horse just above the fetlock joint is 

 attached a kind of leather bracelet fastened by straps. In front 

 of this bracelet, which furnishes a solid point of resistance, 

 are placed various pieces of apparatus. There is, first, a flat 

 box of india-rubber firmly fixed in front of the bracelet ; this 

 box communicates, by a transmission tube, with the registering 

 apparatus. Every pressure exerted on the box moves the 

 corresponding registering lever. It is evident that all the 

 movements of the horse's foot are shown by pressures on the 

 india-rubber box, and are immediately signalled by the regis- 

 tering levers. 



For this purpose, a plate of copper, inclined about 45°, is 



