Fig. 117.—Tracing of the Running of a Man (after Professor Marey.)
D, Pressures and elevations of the right foot; G, pressures and elevations of the left foot.
On the tracing ([Fig. 117]), the line D relates to the right foot; the line G, which is dotted so that it may not be confused with the preceding, corresponds to the left foot. The line G first ascends; the meaning of which is that the left foot presses on the ground; afterwards it descends: this indicates that the pressure of the foot has ceased. It is the same for the right foot. As we see, the pressures succeed each other; when the left foot touches the ground, the right is separated from it; when the latter presses the ground, it is the left which no longer rests there.
The line O is related to the movements of the body, as indicated by the oscillations of the head. We will neglect these.
But this tracing, which serves us for an example, is not, it must indeed be said, of very easy reading; it would be still less so if the paces of a horse were registered, for there would then be four lines, the entanglement of which would cause greater complication.
These difficulties of reading need be no longer feared, if we transform the tracing into a notation by means of the following diagram.
