Fig. 118.
There are drawn ([Fig. 118]) below the graphic tracing two horizontal lines (1, 2). From the point where the line D rises (commencement of the pressure of the right foot), and from the point where this same line descends (end of the same pressure), we let fall two vertical lines joining the two horizontal ones mentioned above. At this plane, and between the two vertical lines, we mark a broad white one (a, b). This expresses, by its length, the duration of the period of pressure of the right foot. In doing the same for the line G, we obtain for the indication of a pressure of the left foot an interval of the same kind, in which are marked cross-lines, or which is tinted gray, in order to avoid all confusion with the preceding tracing.
This notation can, with sufficient exactitude, be compared to that which is employed in the musical scale. The horizontal lines 1 and 2 represent the compass. We there also see notes; these are the bars indicating the pressure, of which the value—that is to say, the duration—is represented by the length of these bars. It is the same with regard to the intervals of silence: these are expressed by the intervals which separate the pressures, and correspond to the moments in which, during certain paces, such as running, the body is raised from the ground. Besides, we see intervals of this kind on the notation reproduced ([Fig. 118]) relative to the running of man.
Fig. 119.
In order to make the signification of these tracings still better understood, we reproduce four varieties of them ([Fig. 119]).
The first notation is that of ordinary walking. The pressures succeed each other regularly.
The second shows what takes place during the ascent of a staircase. At a certain moment, the weight of the body is upon both feet at the same time, one of them not quitting the lower step, until the other is already in contact with the step above. Accordingly, there is thus produced an overriding of the pressures.
The third is relative to running, and has already been represented in [Fig. 118]. The pressures of the feet are separated by the times of suspension.