Demonstration.—Since a complete pack contains 13 cards of each suit, the values of which are 1, 2, 3, &c., as far as 13, the sum of all the spots of each of the different suits will be 7 times 13 (91), which is a multiple of 13; consequently the quadruple is also a multiple of 13: if we add the spots of all the cards, always rejecting 13, the remainder at last must be 0. Hence it is evident, that if a card, the spots of which are less than 13, be drawn, the difference between its spots and 13 will be what is wanting to complete the number. If, at the end, then, instead of attaining to 13, we attain only to 10, for example, it is plain, that the card wanting is a 3; and if we attain exactly to 13, the card missing must be equivalent to 13; that is, it must be a king.
TO TELL TWO CARDS OUT OF TWENTY.
You must retain in your memory the four following words, with the arrangement of the letters which compose them:—
| m | i | s | a | i |
| t | a | t | l | o |
| n | e | m | o | n |
| v | e | s | u | l |
Collect all the cards into the left hand, two by two, as they lay on the table, and then place them, one by one, in the same order as the preceding letters, taking care to place the two first as the two m, the two next as the two i, the two following as the two s, and so on.
Ask each person in which horizontal row his two cards are. If he says they are both in the same row, for example the third, they will be pointed out by the letters n and n, contained in that row; if they are in two different rows, as the first and last, the letters s and s will indicate the place which they occupy.
TO BRING ALL THE CARDS OF THE SAME KIND TOGETHER.
Have in readiness a pack, all the cards of which are arranged in successive order; that is to say, if it consists of 52 cards, every 13 must be regularly arranged, without a duplicate of any one of them. After they have been cut as many times as a person may choose, form them into 13 heaps of 4 cards each, with the coloured faces downwards. When this is done, the 4 kings, the 4 queens, the 4 knaves, and so on, must necessarily be together.
THE FOUR INDIVISIBLE KINGS.
Take four kings, and place between the third and fourth any two common cards whatever, which must be neatly concealed; then show the four kings, and place the six cards at the bottom of the pack; take one of the kings, and lay it on the top, and put one of the common cards into the pack nearly about the middle; do the same with the other, and then show that there is still one king at the bottom: desire any one to cut the pack, and as three of the kings were left at the bottom, the four will therefore be found together in the middle of the pack.