Electroph'orus, an instrument for obtaining electricity by means of induction. It generally consists of a tin mould, A, which in practice is kept in connection with the ground, filled with shell-lac or resin, B, and a movable metal cover, C, with a glass handle, D, as shown in the fig. The shell-lac is poured in when melted, and is mixed with some other substance to make it less brittle. When the apparatus is used, the surface of the resin or the shell-lac is smartly beaten with cats' fur. This electrifies the resin negatively. When the cover is brought near the lower part of the apparatus, it is charged positively on its under surface, negatively on its upper. If then it is touched, the negative escapes, and the cover is charged with + electricity; and if removed and applied to any conductor, it will give a positive charge to it. The process may be repeated for a great number of times with only a small diminution of B's charge, except by connection or dampness. It is usual to have the earth connection made by a metallic pin passing through B to A, or by a piece of tinfoil, e, pasted extending slightly over B, and connected with A.