THE preceding pages have set forth the concrete facts of visible beauty, and the explanation of our feelings about it. It is also interesting, however, to see how these principles are illustrated and confirmed in the masterpieces of art. A statistical study, undertaken some years ago with the purpose of dealing thus with the hypothesis of substitutional symmetry in pictorial composition, has given abundance of material, which I shall set forth, at otherwise disproportionate length, as to a certain extent illustrative of the methods of such study. It is clear that this is but one of many possible investigations in which the preceding psychological theories may be further illuminated. The text confines itself to pictures; but the functions of the elements of visual form are valid as well for all visual art destined to fill a bounded area. The discussion will then be seen to be only ostensibly limited in its reference. For picture might always be read space arrangement within a frame. In the original experimental study of space arrangements, the results of which were given at length on page 111, the elements of form in a picture were reduced to SIZE or MASS, DEPTH in the third dimension, DIRECTION, and INTEREST. Direction was further analyzed into direction of MOTION or ATTENTION (of persons or objects in the picture), an ideal element, that is; and direction of LINE. For the statistical study, a given picture was then divided in half by an imaginary vertical line, and the elements appearing on each side of this line were set off against each other to see how far they lent themselves to description by substitutional symmetry. Thus: in B. van der Helst's "Portrait of Paul Potter," the head of the subject is entirely to left of the central line, as also his full face and frontward glance. His easel is right, his body turned sharply to right, and both hands, one holding palette and brushes, are stretched down to right. Thus the greater mass is to the left, and the general direction of line is to the right; elements of interest in the head, left; in implements, right. This may be schematized in the equation (Lt.)M.+I.=(Rt.)I.+L.