To begin the trick the performer has the ace of diamonds on top of the pack and the trey of the same suit at the bottom. Making the "pass" he brings the two cards together in the center of the pack, and forces the ace of diamonds on one of the audience. The trey is now the bottom card of the top section of the pack. When the pack is closed the performer separates the two packets by inserting between them the little finger of the left hand. When the ace is to be replaced he opens the pack at the place of separation, so that it will be directly under the trey. Putting his little finger between the ace and the trey, he makes the "pass," bringing these cards to their original position on top and at the bottom of the pack. "Now," says the performer, "I will despatch the ace on its travels, by sending it from the middle of the pack to the bottom." He ruffles the pack and shows the ace, apparently, at the bottom. What he really does is to hold the pack at its ends by both hands, the fingers covering the end spots of the trey. Then he covers the face of the cards with his left hand and presses the pack against his fore-head. With his other hand he strikes the hand that holds the pack. This, he says, is to drive the ace through the pack. He removes the pack from his forehead and the ace is seen sticking there. This is effected by having the forehead dampened before beginning the trick.
Removing the ace from his forehead the performer spins it through the air, and catching it as it falls shows that it is really the ace of diamonds. "Now watch it," he says, and once more sets it spinning through the air. Every one can see that it is the ace. This time as it comes down the performer does not touch it, but allows it to reach the ground. "Will some one," he asks, "be good enough to pick it up, and tell us what card it is?" And to the surprise of all it proves to be the trey.
The secret of this is that the performer changes the ace for the trey, and when the latter is spun in the air, by some principle of optics, which is not clearly understood, it is impossible to distinguish the one card from the other, the end spots of the trey seeming to be drawn into the center spot.