COMPARATIVE MEASUREMENT.
This is a very important thing in drawing from Nature, or objects of any kind, and must be thoroughly understood by the student, as without it no drawing can be made absolutely correct.
Comparative measurements are entirely proportional. The manner of taking them is as follows:
Place yourself opposite the object to be measured, at the same distance from which your drawing is taken. Let us say you are drawing the bust of Apollo, and wish to discover just the exact height of the whole, also the width across the shoulders.
Extend your arm in a perfectly straight line at right angles to the cast, holding in your hand a long lead-pencil. The pencil must be held parallel to the general direction of the cast, neither end being allowed to swerve the slightest.
Now, closing one eye to concentrate the vision, measure off with your thumb upon the pencil, which is held crosswise, the apparent distance from the outside of one shoulder in a direct line to the outside of the other. Keep your thumb tightly upon the pencil at the place measured, and slowly turn the hand around, keeping the arm extended at the same distance from the body, and the eye in the same position as before.
The pencil is now held straight up and down, and your object is to see how many times the distance measured off on the pencil will go into the whole length of the cast, beginning at the top of the head and measuring down to the foot of the bust, slowly moving the pencil downward and checking off with the eye each time the measurement is repeated.
In this way we can find out exactly whether the cast is just twice as long as it is wide, or less—in other words, the comparative proportions.
This kind of measurement is invaluable in out-of-door sketching, and the eye soon becomes so trained by practice that relative proportions are compared instinctively, and one scarcely needs to use the pencil.