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:—

1.13110..13219.133
2.23111..23220.233
3.33112..33221.333
4.12113..12222.123
5.22114..22223.223
6.32115..32224.323
7.11116..11225.113
8.21117..21226.213
9.31118..31227.313

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.