Electrical Machine

An instrument for the excitation and collection of electricity. The term is only applied to contrivances in which friction is the immediate cause of the electrical disturbance; those which act through chemical force, magnetism, or heat, being known by various distinctive names, as ‘voltaic battery,’ ‘electro-magnetic machine,’ ‘induction-coil,’ ‘thermo-electric pile,’ . The electrical machines in common use are composed of a hollow gla cylinder, or circular plate of gla , turning on an axis, and rubbing against two or more leather rubbers covered with silk, the electricity being collected by sharp points fixed in a metal rod standing on a gla pillar. A description of these instruments, however, would be out of place in the present work, which does not aim at giving information that may be easily obtained from other sources. Cylinder machines are seldom made of greater size than 13 inches by 9, and are about as powerful as an 18-inch plate machine. The latter are commonly made up to 3 and 4 feet diameter, and will, with a suitable condenser, give 15 inch sparks in air.