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CHAPTER XIV. 



NOTATION OF THE PACES OF THE HORSE. 



That distinguished French savant, M. Marey, pubHshed in 1878 his 

 researches on the paces of the horse. He carried them out by means 

 of a registering apparatus somewhat similar to the one, the sphygmo- 

 graph, used by doctors for recording the movements of the pulse. The 

 machine consisted of a cylinder which was made to revolve by clock- 

 work. Attached to it were four pointed levers that were arranged 

 so as, when pressed upon, to trace lines on a sheet of blackened paper. 

 Each of these levers was provided with an india-rubber tube, which 

 communicated with a rubber ball filled with air and fixed on the ground 

 surface of one of the animal's feet. These levers and their connections 

 were made so that, when the horse during movement put a foot on 

 the ground, the rubber ball attached to that particular foot would be 

 compressed, and the air rushing into the tube would raise the lever 

 and bring its point against the sheet of blackened paper. When the 

 animal lifted its foot from the ground, the air would go back into the 

 ball, and allow the point of the lever to be taken off the surface of 

 the paper. As, while this was being done, the cyHnder revolved at 

 a uniform rate of speed, it follows that the line traced by each lever 

 point would be a record of the duration of the contact of the foot with 

 the ground, and that the intervals between two such contacts would be 

 a measure of the time the foot was suspended in the air. By this means, 

 Marey investigated the nature of the paces of the horse. He also devised 

 the following very ingenious method of representing them on paper. 



If we wish to express on paper the running pace of a man, we may do 

 so by making a scale with rectangles, which, for the sake of conveni- 

 ence, we may use instead of Marey's lines. Thus, if the time of contact 

 be about equal to that of suspension, Fig. 257 will express the nature of 

 the pace. To render this figure more graphic, plain rectangles have 

 been used to mark the supports of the left foot ; and shaded ones, those 

 of the right foot. If we desire to represent the ordinary walk of a man 

 in the same manner, we shall be confronted with the difficulty that, 



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