These are the simplest signs; but some of the Greeks have a great
number of them, to designate everything; and even sometimes to
communicate and receive intelligence, when necessary. This
telegraphy is so imperceptible that it is difficult to describe
it, and altogether impossible to detect it.
 Tricheries des Grecs devoilees.
Robert-Houdin has exhausted the subject of card-trickery, in
connection with that prestidigitation which, it seems, all card-
sharpers cultivate, the description of which, however, is by no
means so entertaining as the visible performance. I find,
nevertheless, in his book, under the title of 'Small Trickeries
made innocent by Custom,' certain things alluded to which I can
attest by experience.
I. At Whist, no communication whatever must be made by a player
to his partner, excepting those authorized by the laws of the
game; but some persons go further, and by the play of their
features 'telegraph' to their partners the value of their hands.