The plumb-line affords another method of testing. A thread or a string with any small object for a weight attached to one, end, is Hold the string so that it hangs vertical and motion less, and at the same time covers some important point in the ob ject. By looking up and down the line the points directly over and under the given pOint can be determined and the relative distances of other important points to the right and left can be calculated. The plumb-line will also determine all the vertical lines in the object and help to determine divergence of lines from the vertical.
A ruler; a long rod, or pencil held in a perfectly horizontal . position is also of assistance in determining the width of angles and divergences of lines from the horizontal., 25. Misuse of Tests. The use of tests • may easily be per 'verted and become mischievous. Since the object of all draw ing is to train the hand and eye, it follows naturally that the more the student relies upon tests the less will he depend upon his per ceptions to set him right, and the less education will he be giving to his perceptions. There is no greater mistake for a student than to use the measuring test before making a drawing. Spend any amount of time in calculating relative proportions by the eye, but put these down and correct them by the eye, not once but many times before resorting to tests. All the real education in drawing takes place before the tests Are made. Let the student remember that the tests may help him to make an accurate drawing, but they will never make him an accurate in the true sense. Nothing but training the eye to see and the hand to execute what the eye sees, will do that. When the student has reached the end of his knowledge, has corrected by the eye as far as he can, then by applying tests he is enabled to see how far his percep -tions have been incorrect. That is the only educational value of the test. Merely to make an accurate drawing with as little men tal effort as possible, relying upon test measurements, requires considerable practice and skill in making the tests, but gives very little practice or training in drawing.
26. Light and Shade. Objects in nature, as before explained, detach themselves from each other by their differences in color and in light and shade.
In drawing without color, artists have always allowed themselves a very wide range in the amount of light and shade employed, extending from drawing in pure outline up to the representation of exact light and shade, or of true values, as it is called.
Drawings which contain light and shade may be divided into two classes: Form drawing, which is from the point of view of the draftsman, and value drawing, which is from the point of view of the painter.
27. Form Drawing. In form drawing aim, as the name implies, is to express form and not color and texture. In order to do this, shadows and cast shadows are indicated only as far as they help to express the shape. This is the kind of drawing practiced by most of the early Italian masters, and it has been called the Florentine method. It is often a matter of careful out line with just. enough shadow included to give a correct general ' impression of the object. There is usually little variety in the shadow and no subtle graduations of tone, but the shadows are indicated with sufficient exactness of shape to describe the form clearly. Form drawing is a method of recording the principal facts of form with rapidity and ease and of necessity deals only with large general truths. Perhaps its most distinguishing feature is that it does not attempt to suggest the color of the form.
28. Value Drawing. The word value as it is used in draw- • ing is a translation from the French word valeur, and as used by artists it refers to the relations of light and dark.
Value drawing represents objects exactly as we see them in nature; that is, not as outline, but as masses of lights and darks. In value drawing the artist reproduces with absolute truth the dif ferent degrees of light and shade. While form drawing suggests relief, value drawing represents it, and it also represents by trans lating them into their corresponding tones of gray, the values of color. In form drawing, a draftsman representing a red object and a yellow one, would be satisfied to give correct proportions and outlines with one or two principal shadows, while a value drawing of the same objects would show not only the relation of the shadows as they are in nature, but also the further truth that the red object was as a whole darker than the yellow one. The light side of the red object might even be found to be darker in value or tone than the shadow side of the yellow form.