Take a full set of dominoes--twenty-eight pieces--turn them face
downward on the table; shuffle them thoroughly; then tell the company to
turn them over and match them in the ordinary way, while you take a seat
at the other end of the room with your back to the table. They can
blindfold you if they wish. As soon as all the pieces are matched you
call out the numbers shown at the two ends of the row. Return to the
table, turn the dominoes over again, shuffle them as before with the
right hand; again turn your back, and call out the end numbers. You can
repeat this any number of times without detection, unless some one
should count the pieces and find only twenty-seven. Each time you have
shuffled them you have dropped a piece concealed in your right hand, and
extracted and palmed another. One piece taken from a set of dominoes
invariably indicates by its numbers the numbers at the two ends of a row
when the pieces are all properly matched.