The sections in [Figs. 2 and 3] explain the construction, and show how the ball is brought into the desired position to cause equilibrium.
Corresponding to the point where the halves of the egg are soldered together, there is internally a partition that has the form of a channel, of semicircular section, which runs around the tube, T. The ball, B, when the egg is held vertically, is capable of revolving around this tube, T, and as long as it remains in the channel will cause the egg to fall every time the operator endeavors to make it stand on its base, c. The egg can stand upright only on condition that the ball be made to pass from the upper to the lower compartment, in which case it will take the position, B′′′, at the base of the egg. This result is reached as follows: The central tube contains, just beneath its upper extremity, an aperture, B′′, that forms a communication between the two compartments, and that is sufficiently large to allow the ball to pass through. Two small guides start from the side of the egg, and follow the contours of the partition up to the orifice in the central tube. On a line with the orifice, and on the outside of the egg, there is a small and scarcely visible point, o. If the egg be sufficiently inclined toward this latter, as in [Fig. 3], the ball will take the position, B′, at the beginning of the guides leading to the orifice, B′′. If at this moment the egg be gently turned back in the opposite direction, the ball, being kept in the plane formed by the point, o, and the egg’s axis, will run along the guides and drop through the orifice into the lower compartment. When the egg is righted, the ball will take the position, B′′′, at its base, and the egg will then stand upright. By turning the egg upside down, the ball may be made to enter the upper compartment again, and things will then be as before.
FIGS. 2 AND 3.—DETAILS OF CONSTRUCTION.
With a little practice and skill, it is not even necessary to look for the position of the point, o, and thus run the risk of showing the uninitiated how the trick is done. On giving the egg a slight angular motion, the hand will feel the passage of the ball over the slight projection formed by the guides; the ball will naturally seat itself upon the latter, and the double motion above mentioned will accomplish the desired result. Effected in this way, and the hand being covered with a handkerchief, the mode of operating will not be perceived by the uninitiated spectator.