The Magnetic Cards

Draw a pasteboard circle; you then provide yourself with two needles,

similar to those used in the foregoing experiment, (which you must

distinguish by some private mark,) with their opposite points touched

with the magnet. When you place that needle whose pointed end is

touched, on the pivot described in the centre of the circle, it will

stop on one of the four pips, against which you have placed the pin

in the frame; then take the needle off, and, placing the other, it

will stop on the opposite point.



Having matters thus arranged, desire a person to draw a card from a

piquet pack, offering that card against which you have placed the pin

of the dial, which you may easily do, by having a card a little longer

than the rest. If he should not draw it the first time, as he probably

may not, you must make some excuse for shuffling them again, such as

letting the cards fall, as if by accident, or some other manoeuvre,

until he fix on the card. You then tell him to keep it close, and not

let it be seen. Then give him one of the two needles, and desire him

to place it on the pivot, and turn it round, when it will stop at the

colour of the card he chose; then taking that needle off, and

exchanging it, unperceived, for the other, give it to a second person,

telling him to do the same, and it will stop at the name of the

identical card the first person chose.