Excerpt from: “What to draw and how to draw it” by Lutz, Edwin George, b. 1868
Published c1913 Publisher [New York]: Dodd, Mead
INSTRUCTIONS: Beginning with number one, then number two, and so on — show how to go on with your drawing.
They give the order in which to make the various strokes of the pencil that together form the completed picture.
The dotted lines indicate where light lines are drawn that-help in construction — that is; getting proportions correctly, outlining the general form, or marking details in their proper places.