DESCRIPTION OF APPARATUS. 



149 



connected at its upper extremity with a kind of hinge, whilst 

 its lower end is fastened by a solid wire to the upper face of 

 the india-rubber box, on 

 which it presses by means 

 of a flat disc. On a wire 

 parallel to the slip of 

 copper slides a ball of lead, 

 the position of which can 

 be varied in order to in- 

 crease or diminish the 

 pressure which this jointed 

 apparatus exerts on the 

 india-rubber box. 



The function of this 

 apparatus is analogous with 

 that of the instrument re- 

 presented in fig. 28, in- 

 tended to show the re- 

 actions which are produced 

 in various kinds of loco- 

 motion ; only the inclina- 

 tion of the oscillating por- 

 tions allows them to act on 

 the membrane during the 

 movement of the elevation, 

 the descent, and the hori- 

 zontal progress of the foot. 



When the hoof meets 

 the ground the ball has a 

 tendency to continue its 

 motion, and compresses 

 with force the india-rubber 

 box. When the foot rises, 



the inertia of the ball produces in its turn a compression 

 by a kind of mechanism already described with reference to 

 fig. 28. 



Through the kindness of Mons. Pellier, we have been able 

 to experiment on several horses, ridden by himself, while 

 holding in his hand the registering instruments. 



Fig. 43. — Apparatus to give the signals of 

 the pressure and rise of the horse's hoof. 



