The cyclegraph method permits us to record, measure, and see this orbit or exact path of a motion or cycle of motions. Small electric lights are attached to the hands, or any other members of the body involved in the motion. A photographic plate or film is then exposed while the motion is made, with the result that a path of light, which resembles a white wire, is seen upon the developed plate, representing the path of the motion. The effect is best gained by a stereoscopic photograph, which shows this path in three dimensions. The chronocyclegraph method enables us not only to see the path of the motion, but also its directions, and the duration of the entire motion and of its elements. These chronocyclegraphs are made by attaching lights to the moving parts of the body, or machine, as in the cyclegraph, and by introducing a properly timed, pulsating interrupter in the circuit, which may be adjusted not only to record the time and duration, but also to record these with different graphs, representing the paths of each of several motions made by various parts of the body and their exact distances, exact times, relative times, exact speeds, relative speeds, and directions. [Illustration: FIG. 20 This picture shows a lamp attached to the hand for the purpose of taking cyclegraphs or chronocyclegraphs of motions in connection with obtaining motions of least fatigue.] [Illustration: FIG. 21 This picture shows an experiment that was carried on by us some time ago for determining the laws pertaining to the times and fatigue of motions of different lengths. The operation studied is that of moving a seven pound weight. The times are divided into three parts: Length of time from starting to picking up weight; length of time from picking up weight to depositing; and length of time of recovery to standing position from depositing. The experiment proved that the time of motions of different lengths is practically the same unless those of the same length are consecutively repeated. The quantity of work that can be done in a day is, of course, much less with long motions than with short ones, due to extra time needed to overcome the fatigue of the long motions.] By means of the “penetrating screen,” it is possible to pass a cross-sectioned plane in any direction through any desired plane, or through any number of planes in the cubic space under observation. This makes it possible to record the data with great accuracy in three dimensions, and to read the information from the data easily.