it assists us to draw correctly, as the grammar of a language helps us to speak and write correctly.
In the first place let us consider proportions.
If you are sitting at your work, lean back in your chair and face the object that you are drawing, and hold a pencil or ruler
up at arm's length and level with your eyes. Close one eye and measure from one end of the ruler, or pencil, to the thumb, then swing the hand—still at arm's length—and compare the measurement with another portion of the same object.
Look at your drawing.
Compare the same proportions in your drawing. The proportions must agree.
Let us presume that you are drawing a simple subject such as a small basket and you are in doubt as to whether the depth of your drawing of the basket is too great for its width.
