In the four sides of a cube box, measuring 18″ each way, make an oval opening, 9″ by 7″, as A, B, C, D in [Fig. 9]. Inside the box place two mirrors, back to back, diagonally from G to E ([Fig. 10]), and contrive four curtains to draw up simultaneously over the holes.
Fig. 9.—Showing box with oval openings.
Fig. 10.—Showing box with oval openings and mirrors.
You must now get two couples to look through the holes, arranging the two men opposite each other, as at A and C, and the ladies at B and D, promising them that by looking into the simple but magical box they shall see the future partners of their lives and pleasures.
As soon as they are in position raise the curtains, when A will see B, and C will be gazing at D, so that if you have sorted the parties aright, they will feel so pleased with themselves and with you that no inquiry will be made as to how the trick is done.
To turn from sight to hearing, the following is a simple experiment which can be exhibited without any special apparatus.
Cut a plain cross from a sheet of notepaper, as in [Fig. 11], and place it over a wine-glass, bending the ends to prevent it slipping off. Almost fill the glass with water, taking great care to leave the sides and rim perfectly dry.
If you damp your finger and pass it over any part of the glass outside, a distinct humming will be heard, but the more remarkable thing to observe is that the cross will begin to revolve very slowly so long as your finger rubs a portion of the glass between the arms of the cross—as at A in [Fig. 11]. Yet when you begin to rub beneath one of the arms the paper will remain perfectly still. A complete revolution of the paper can be produced by rubbing round the glass in a circle.