Figure Drawing

T seems very formal, very didactic, to say that the representation of solid forms in line is based upon the drawing of the cube and the cylinder, and the statement is certainly an exaggeration, but as a practical rule the assertion is true enough. The principle involved is seen in Fig. 1, and briefly is—that a cylinder seen in a foreshortened position is expressed by a curved line, an oval, at either end, and that a cubic form is represented by two lines at an angle, also at either end of it. It will be clear to any one without further explanation that modifications in the form will be followed by modifications in the degree, and kind, of curvature, or angle. However varied the form may be, its expression by line will depend upon the simple law thus indicated. From this law of foreshortening we deduce this axiom—that where two similar lines, as A and B in Fig. 2, occur one beyond the other, the inference is that the smaller (according to perspective) is the more remote and that the surface from A to B recedes. Such a shape as C, if symmetrical side for side, may be a plane receding upwards, or may be a shape seen in its true form, without foreshortening. An addition at the side, as at D, suggests that the form is receding, but only if the bottom line of the addition, d, slopes down. Of course where such is the case the form EF is truer, because the side FF would become shorter than EE. It would often be impossible to tell which end was the nearer without an edge, or side, as shown at H. This edge (H) at once indicates that the smaller end is really the nearer, and that we are looking up at the object. This edge belongs to the cube form—it is the return, or third side, and indicates the nearer end.