DEMONSTRATION IV. Have a map laid open on the table, and have the
audience decide upon a trip between two points, either by rail or by
water. Then returning to the room, stand as above described, and with
your forefinger find the place from which the trip starts. Then move
slowly along the selected course in the same manner in which the
checker-game was played, passing along the chosen route until the end
is reached. These feats are all really variations of the one principle.