NEW RESULTS IN ANIMAL MOVEMENTS. 447 



suffices to join the body, by means of a rigid connection, with a writing- 

 lever, which touches a revolving cylinder, covered with smoked paper. 

 The tracer on the writing-lever, moved with variable velocities, and 

 in a direction parallel to the axis of the cylinder, will draw sinuous 

 curves, whose parts will indicate by their inclination the velocities of 

 the motions which produced them. 



But the motions in walking are too extended to be traced on the 

 revolving cylinder in their real magnitudes ; in order to reduce them, 

 while at the same time I preserved their characteristics unaltered, I 

 had recourse to a train of wheel-work. In this apparatus, each wheel 

 working into another, whose teeth are ten times more numerous than 

 those of the former, it follows that the motion communicated to the 

 first axis will be reproduced by the second with a reduction of -^ ; the 

 third axis will reproduce the motion reduced to y^-g- ; and the fourth 

 axis will reduce it to y^Vo"? etc 



If we attach to the foot of a walker a thread, which is wrapped 

 around the wheel on the first axle of the wheel-work, and if to the third 

 axle we connect the writing-lever, we can obtain traces on the revolv- 

 ing cylinder which will have only y^th of the extent of the paths gone 

 over by the foot of the walker. 



Fig. 1 shows five traces obtained from the foot when walking with 

 various velocities. A has been produced by the slowest walk ; JB is 

 the ordinary gait ; while G is the most rapid : the remaining traces 

 have been obtained from gaits less rapid than that of C. 



Fig. i. 



(The figure represents the smoked paper, unrolled from the re- 

 volving cylinder after the experiment. The paper revolved with the 

 cylinder in the direction from to T. Therefore, the axis of the 

 cylinder was parallel to OX, and the tracer on the writing-lever moved 

 parallel to OX. It follows that, if the foot had remained stationary 

 while the cylinder revolved, the tracer would have described a straight 

 line parallel to OT. CII is the trace of the vibrating tuning-fork ; 

 each bend of its sinuous line is equal to ^th of a second of time. This 

 chronographic trace gives us the means of estimating accurately the 



