Volume 2

A manual for students preparing for examination at Apothecaries' Hall, or other medical examinations / by John Steggall.

  • Steggall, John, 1795?-1871.
Date:
1838
Catalogue details

Licence: Public Domain Mark

Credit: A manual for students preparing for examination at Apothecaries' Hall, or other medical examinations / by John Steggall. Source: Wellcome Collection.

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    depends more upon the rubber than on the glass or the resin. A thread in a known electrical state is used as a test of the quality of the electricity in another body. The cat’s back is said to be positive to all known substances, and glass stands next to it in order. Sealing-wax is negative to most light subtances, but to the metals it is a positive electric. All bodies contain electricity in a latent or qui- escent state, that is, the two fluids are supposed to be in a state of neutralization. When electri- city is evolved the balance is disturbed, or a separation of the fluids is supposed to take place. This separation is accomplished in various ways, as by friction, change of temperature, form, con- tact, chemical action, &c. When two substances, if conductors and insu- lated, be rubbed together, each containing posi- tive and negative electricity, it is supposed that the fluids are separated, and that all positive electricity collects in one and negative in the other. If, however, the substances thus rubbed be either both non-conductors, or one a non-con- ductor, the electric action is not manifested when they are kept in contact, and only when such bodies are separated. . A copious supply of electric fluids is obtained by the aid of the electrical machine, which con- sists of a cylinder or plate of glass, with a rubber, the latter made with leather stuffed with horse- hair or wool, and coated with some amalgam. The cylinder or plate revolves onan axis, and is raised from the ground by wooden pillars, or a support ;