This mirror must be placed against a partition, through which is to go two strings, by which an assistant in the adjoining room can easily move the glass in the grooves, and consequently make the card appear or disappear at pleasure.
Without an Assistant.—Place a table against the partition, and let the string from the glass pass through a hollow leg of it, and communicate with a small trigger, which you may easily push down with your foot, and at the same time be wiping the glass with your handkerchief, that the card may appear the more conspicuous. It may also be diversified by having the figure of a head, say of some absent friend, in the place of the card.
Matters being thus prepared, you contrive to make a person draw the same sort of card with that fixed to the mirror, and place it in the middle of the pack: you then make the pass, and bring it to the bottom; you then direct the person to look for his card in the mirror, when the confederate behind the partition is to draw it slowly forward, and it will appear as if placed between the glass and the quicksilver. While the glass is coming forward you slide off the card from the bottom of the pack, and juggle it away.
The card fixed to the mirror may easily be changed each time the experiment is performed. This trick may be also made with a print that has a glass before it, and a frame of sufficient width, by making a slit in the frame through which the card is to pass; but the effect will not be so striking as in the mirror.
THE DIVINING SPY-GLASS.
Let a small perspective glass be made, that is wide enough at the end where the object-glass is placed, to hold a table similar to the following:—
| 1.131 | 10..132 | 19.133 |
| 2.231 | 11..232 | 20.233 |
| 3.331 | 12..332 | 21.333 |
| 4.121 | 13..122 | 22.123 |
| 5.221 | 14..222 | 23.223 |
| 6.321 | 15..322 | 24.323 |
| 7.111 | 16..112 | 25.113 |
| 8.211 | 17..212 | 26.213 |
| 9.311 | 18..312 | 27.313 |
Take a pack of cards that consists of 27 only, and giving them to a person, desire him to fix on any one, then shuffle them and give the pack to you. Place the twenty-seven cards in three heaps, by laying down one alternately on each heap, but before you lay each card down, show it to the person without seeing it yourself; and when the three heaps are finished, ask him at what number, from 1 to 27, he will have his card appear, and in which heap it then is. Then look at the heap through the glass, and if the first of the three numbers which stands against that number it is to appear at, say 1, put that heap at top; if the number be 2, put it in the middle; and if it be 3, put it at bottom. Then divide the cards into three heaps, in the same manner, a second and a third time, and his card will then be at the number he chose.
Example.—Suppose he desire that his card shall be the 20th from the top, and the first time of making the heaps he says it is in the third heap; you then look at the table in the perspective, holding it at the same time over that heap, and seeing that the first figure is 2, you therefore put that heap in the middle of the pack. The second and third times you in like manner put the heap in which he says it is, at the bottom, the number each time being 3. Then looking at the pack with your glass, as if to discover which the card was, you lay the cards down one by one, and the twentieth card will be that he fixed on.