Fig. 40.—Base for Heliograph.
Fig. 41.—Back View of Heliograph.
Make a block of wood 4 inches long, 1 inch wide and 1 inch thick and bore a ¼ inch hole through it near one end. To the other end of this stick fasten a mirror about 4 inches square. This mirror should be perfectly smooth—a plate glass mirror is the best—and have a hole ¹/₁₆ inch in diameter drilled through the center of the mirror for sighting the heliograph, as shown in [Fig. 41]. Any optician will drill the hole for you for a quarter or less. [Fig. 42] shows a top view of the heliograph and [Fig. 43] shows a side view of it.
Make a wood frame so that the mirror can be fastened in it and screw the frame to a stick of wood. Get a bolt 5 inches long and ¼ inch in diameter and have a thumb screw fitted to it. Set the end of the stick which has the mirror fastened to it into the slotted end of the baseboard, push the bolt through the holes and after slipping on the washer put on the thumb screw. The mirror can now be moved to and fro.
Fig. 42.—Top View of Heliograph.
Fig. 43.—Side View of Heliograph.
Into the hole in the front part of the base put a wire or a thin round stick to sight the mirror by. The heliograph is now ready for use.