A hand-book of materia medica and therapeutics : with twenty-nine illustrations : being a portion of An analytical compendium of the various branches of medicine / by John Neill and Francis Gurney Smith.
- John Neill
- Date:
- 1852
Licence: Public Domain Mark
Credit: A hand-book of materia medica and therapeutics : with twenty-nine illustrations : being a portion of An analytical compendium of the various branches of medicine / by John Neill and Francis Gurney Smith. Source: Wellcome Collection.
Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)
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![touching the resin and receiving some of its electricity, it will boob be repelled by it; but on the other hand, attracted by the glass. This experiment establishes the law that bodies similarly electri- fied, repel each other, but dissimilarly electrified they attract. Electricians divide bodies into electrics, or nonrconductors, as g] resin, sulphur, &c., and non-electrics or conductors, as the metals, water, &c. The essential parts of the electrical machine, arc, 1, the electric, which is usually a glass cylinder or plate, contrived so as to be capable of turning by means of a handle; 2, the rubber, which is a stuffed cushion covered with an amalgam of tin, zinc, and mer- cury, against which the electric is rubbed; 3, the prime conductor, which is a metallic cylinder armed with a number of points for the more perfect collection of the electricity. Both cushion and con- ductor should be insulated, that is, supported on a pedestal of glass which is a non-conductor. The cylinder, as it turns, becomes charged with positive (vitreous) electricity, by friction against the cushion, and is as quickly discharged, by the rows of points, into the prime conductor, which, as it is insulated, thus acquires a charge of posi- Fig. 8.' tiye electricity, which it will yield up on contact with any body, with a peculiar noise and spark. The maximum effect is produced when the rubber is made to communicate with the earth by means of a chain. If negative electricity be wanted, the conductor must be made to communicate with the earth, and the rubber insulated, the electricity being drawn from the latter.](https://iiif.wellcomecollection.org/image/b21143559_0022.jp2/full/800%2C/0/default.jpg)
