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40 THE BOY ELECTRICIAN

the pattern shown in Figure 35. They should be made one
inch and one-half wide at the wide end and three-quarters
of an inch at the other end. They are each four inches
long. Thirty-two such sectors are required. The easiest
way to make them is to cut out a pattern from heavy card-
board to serve as a guide.

Clean and dry both of the glass plates very carefully and
then give them each two thin coats of white shellac. After
they have been dried, lay one of the plates on the paper
pattern so that the outside of the plate will coincide with
the largest circle on the paper.

Then place a weight in the center of the plate so that it
will not move, and stick sixteen of the tinfoil sectors on the
plate with thick shellac. The sectors are arranged symmet-
rically on the plate, using the eight-inch and sixteen-inch
circles and the radial lines as guides. Both plates should
be treated in this manner. Each sector should be care-
fully pressed down on the glass, so that it will stick
smoothly without air-bubbles or creases. When all the
sectors are in place the plates will appear like that shown
in Figure 3 5.

The Bosses will have to be turned out at a wood-working-
mill or at some place where they have a turning-lathe. The
bosses are four inches in diameter at the large end and one
inch and one-half at the other. A groove is turned near
the small end of each to accommodate a. round leather
belt.

A hole should be made in each boss about half-way

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