These various types of motion study supplement rather than supplant one another. Motion study is primarily for the purpose of observing the variables that affect such study, and for arousing such co-operation between observed and observer, as will make possible the testing of the differences of the effects of the variables. Micromotion study provides for an accurate record of what happened, with all such attending circumstances as appeal to the eye. It is the greatest aid in transference of skill and experience from a worker who has it to one who does not possess such skill and experience. The cyclegraph is useful in providing a simple, easily understood record of the path that any activity followed. The chronocyclegraph is most valuable when the activity is complicated, and when the time and direction of the elements of the motion must be visualized continuously in order to analyze, measure, synthesize, and standardize the process. The penetrating screen, finally, is useful in recording the three dimensional paths and speeds of even the smallest unit of activity. These methods of applying motion study have been patented, but have been for years freely at the disposal of the colleges, which have begun to use them as means for recording accurately scientific data of various kinds. They have justified themselves as more accurate than ordinary records of activity, and have within recent times been put on a basis which makes their cost compare favourably with less accurate methods of measurement. What is more, we have discovered in our data, especially in the chronocyclegraphs, direct records of fatigue, that we believe are the first records of fatigue ever made under industrial conditions. The micromotion films also show breaks in well established habits of several motions that are undoubtedly due to fatigue, but the irregularities in the orbit line, that appear in the cyclegraphs, and that must, because of close control of the variables, be due to the fatigue alone, are more impressive from the physiological viewpoint. [Illustration: FIG. 22 Typical chronocyclegraph of the motion and fatigue study of a bricklayer, laying three bricks in the old method.] [Illustration: FIG. 23 Typical cyclegraph of motion and fatigue study on a drill press, showing cyclegraph of path of motions of the left hand.] [Illustration: FIG. 24 Typical chronocyclegraph of compositor setting type by hand.] Testing the Work by Motions Required.