"Find the centre of each of those lines."

"Easy again," said the boy, as he set his compasses at 78 of an inch, and from the centre of the circle cut each of the straight lines with an arc. ([Fig. 22].)

"Draw a semicircle from each of these points with a radius of 58 of an inch."

"Easier still," quoth Harry, as he drew the semicircles. The drawing then looked like a ([Fig. 22]).

Fig. 22. Pulley design

"Now," said the teacher, "let me show you something." He made a few strokes with the compasses, and the drawing as shown at b was finished. "That is enough for to-day. The compasses are about the easiest of all instruments to use, provided you keep in mind that the pencil point needs to be sharpened to a chisel, or flat shape, the same as any other drawing pencil. The number of designs which may be made with it are simply endless, as you will learn later on."