A STUDY IN LOCOMOTION. 



3 2 3 



tutes an elastic intermediary which suppresses the shocks. But it is 

 not the ordinary dynamometer which I have used in my experiments, 

 but a special dynamometer which undergoes under the strongest trac- 

 tions only an almost insignificant elongation. This elongation, ampli- 

 fied by certain organs and transmitted to a distance by a lever fitted 



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Fig. 3. Tracing of the dynamograph for a vehicle drawn with an elastic intermediary. 



with a pen, is recorded in the form of a wavy curve in conditions re- 

 ferred to above. To sum up, in the employment of animated motors 

 for the drawing of burdens, to find out wherever they produce shocks 

 and vibrations, and to absorb them in elastic springs which restore to 

 useful work a force that seemed only to destroy vehicles, tear up the 



Fig. 4. Tracing of the dynamograph for a hand-barrow drawn by a rigid trace. 



roads, cause the animals to suffer such is the direction in which much 

 progress has been realized, and much more may still be realized. 



2. Of the Speed of Animated Motors. I shall perhaps astonish 

 many of you by saying that the speed of a vehicle is one of the things 

 most imperfectly known. It is generally believed to be sufficiently ex- 

 pressed by stating how much way has been made and how much time 

 has been occupied for that. I have come, you may say, from the Pont de 

 Sevres to the Madeleine in 41 minutes ; the road is well mile-stoned, 

 I possess a good watch ; what greater precision do you require ? As- 

 suredly you have measured accurately the space traversed and the time 

 employed, but that constitutes only the expression of a mean speed 

 resulting from a series of variable speeds, of accelerations, of retarda- 

 tions, and sometimes of stoppages where time is quite unknown. A 

 rigorous measurement of rates supposes the road traversed by the ve- 

 hicle at each instant ; in other words, the position which it occupies 

 upon the road. It is thus that physicists have determined the accel- 

 erated motion of the fall of bodies Galileo and Atwood, by means 

 of successive measurements, Poncelet and Morin by means of that ad- 



