A MAGNETIC DIVER.
This is a mystifying piece of apparatus to those who do not know its secret. The little diver apparently travels up and down from the bottom of a jar full of water to the surface at a word of command.
The diver consists of a small glass test tube about two inches long having the figure of a man painted upon it. The lower end is closed by a very small cork through which is pushed a large iron tack with the head on the outside. The test tube contains just enough water to float head up even with the surface of the water. The exact amount of water required to just permit enough buoyancy for the diver to rise again to the surface after he has been to the top will have to be determined by careful experiment.
The jar containing the diver should be set on a table having a drawer in which a pair of powerful electromagnets can be placed directly under the jar. The electro-magnets are connected to a strong battery and a switch located under the rug or carpet and so arranged that it may be closed by stepping on it lightly and without attracting attention. If the diver does not have too much bouyancy the attraction between the tack and the electro-magnets when the switch is closed should be sufficient to cause him to descend to the bottom of the jar. When the current is turned off the diver should rise again.
[Illustration: FIG. 190.—The Magnetic Diver.]