The electrophorus consists of a square steel base plate, which has a polystyrene plate fastened to it. Polystyrene has one of the highest specific inductive capacities of the common insulating substances. The aluminum plate has its edge turned up so that the charges will not easily escape from this turned edge. On days which have little moisture in the air it is possible to draw a spark about half an inch long from this electrophorus. Of course, like all electrostatic accessories the electrophorus will perform better on some days than on others. The electrophorus is charged in the usual manner by rubbing or striking the insulating material with a cat skin, placing the aluminum plate on the electrophorus, touching it with the finger, removing the finger, and then removing the aluminum plate by means of the hard rubber handle. When the knuckle is brought to the aluminum plate a large spark will then result. The method of grounding the plate before lifting it off may be varied by connecting the steel plate base of the electrophorus to the aluminum plate be means of a wire, or by means of the adjustable Leyden jar discharging tongs.
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