Instructions on making a "telltale" mirror are here given. Get a piece of 3/4-in. by 3/4-in. angle zinc for the frame, mitre together to size, 8 in. by 6in. or 10 in. by 7 in., and solder the angles. Take the thread off two 1-in. No. 8 brass screws, to form the pins A. Drill a hole in the top and in the bottom of the frame; in. from the edge, and countersink these holes on the inside to receive the heads of the screws.

Fix the latter with solder. Now cut in the piece of silver plate, and bed it in the frame with red-lead putty, making the joint watertight. Place over the back of this a piece of two-ply VVillesden paper and a piece of deal board. Cut in between the frame a piece of zinc, and solder round the joint, making all level. Paint the frame black. To fix it on the window-frame, get two small brass angle brackets and drill holes in them to receive the pins on the frame, and fix as shown. Any angle required can be obtained, but it must be tested when fixing. Fig. 1 is an elevation, and Fig. 2 a section of the mirror.

Fig. 2. Tell-tale Mirror.