•WALKING. 



121 



registering levers are displaced by a quantity proportionate to 

 the space passed through. 



For this purpose the cylinder is placed on the axis round 

 which the instrument turns, and on the central end of one of 

 these revolving arms the registering instruments are fixed. 

 The ratio of the radius of the cylinder to that of the circle 

 described by the person walking, allows us to estimate in the 

 tracings the length of the space passed through at each instant. 

 This ratio was 50 to 1 in our experiments. 



Thus, in the tracing obtained, if from one point to another 

 we reckon an interval of a centimetre, this corresponds with 

 50 centimetres passed over on the ground by the person 

 walking. This first notion would be but slightly interesting 

 in itself, since it would teach us nothing more than what we 

 learn concerning the intervals between two positions of the 

 feet, as measured on the ground. The impressions left by 

 our steps on soft ground would furnish in a very simple 

 manner this measurement. But if, in addition to this know- 

 ledge of the space traversed, the tracing gives us the intima- 

 tion of the time passed in traversing it, we are provided 

 with a method of estimating the rapidity of the advance of the 

 body at every instant. 











& 



Fig. 25. — D. Tracing of the impact and rise of the right foot, furnished by 

 a lever subjected at the same time to 10 vibrations per second. It is 

 seen that the vibrations occupy more space at the end of the pressure 

 of the foot ; this expresses the greatest rapidity of the advance of the 

 body at this moment. The same acceleration is observed at the end of 

 the period of support of the right foot ; this is explained by the action 

 of the left foot, w^hich is, at this moment, at the end of its pressure. 



Fig. 25 shows (line D) the tracings of the impact and rise 

 of a limb, and those of the vibrations of a chronograph 

 inscribed simultaneously. To obtain these tracings, we cause 

 to converge at the same time, on the same lever-drum, two 

 transmitting tubes, one of which conveys the variations of 



