448 THE POPULAR SCIENCE MONTHLY. 



duration of each step and the velocity of the foot at each instant 

 while it is swinging in the air. The spaces gone over by the tracer, 

 as before stated, are x&Tr tD of the real distances traversed by the foot ; 

 that is, one centimetre on the paper equals one metre gone over by 

 the foot.) Hence, every thing relative to the transport of the foot in 

 walking is expressed in this figure. 



1. Velocity of the Gait. This is expressed by the general incli- 

 nation of the curve, or by the relation existing between the lengths 

 parallel to OX and to Y. As the different traces contained in the 

 figure correspond to the same distance (three metres and a half; 

 marked on the left-hand vertical line of the figure) gone over in va- 

 riable times, it follows that the relation of these times to this distance 

 will give the velocities of the different gaits. If we count on the chro- 

 nograph-trace the time included between the beginning of each curve, 

 and its termination in the line A, B, (7, we shall have the measure of 

 this time. (For example, the time occupied in going over 3^ metres 

 with the gait B is given by counting the bends of the tuning-fork 

 trace contained between 2 and the perpendicular line let fall from B 

 on to the chronograph-trace.) Thus, for the slow walk from 1 to A, 

 we count thirteen seconds ; the more rapid walk from 2 to B occupied 

 six and a half seconds ; while with the rapid gait the distance from 5 

 to G was traversed in two seconds. 



2. Alternate Periods of Rest and of Motion of the Foot. It is 

 evident that, whenever the traces show an horizontal line (that is, a 

 line parallel to OY), those portions of the traces correspond to the 

 traces made while the foot touched the ground and was immovable, 

 since the spaces then gone over are nothing. The traces show that the 

 duration of the periods of repose decreases as the gait is accelerated. 

 The time during which the foot is in motion is shown by the oblique 

 lines whose projection on the trace of the chronograph increases, 

 relatively to the periods of repose, as the gait is more rapid. This 

 proves that the length of the step increases with the velocity of the 

 gait. 



We can also, from the traces, estimate with precision the relation 

 of the velocity of gait to the length of step, the relative variations of 

 the duration of the periods of repose and of motion of the foot, etc. ; 

 but we will not here dwell on these details ; the essential point under 

 consideration is the following : 



3. The Nature of the Movement of Translation of the Foot. The 

 trace of this movement is shown in a line which is nearly straight in 

 all of its parts ; the motion of the foot is therefore uniform during 

 nearly the whole of its translation ; the inflections of the line at its be- 

 ginning and at its end show that, in rapid gaits especially, the motion 

 of the foot begins and ends in short periods of variable velocities. 

 From the above we are now able to judge how far the oscillation of 

 the leg is analogous to that of a pendulum. 



