An essay on electricity : explaining the principles of that useful science, and describing the instruments, contrived either to illustrate the theory, or render the practice entertaining : illustrated with six plates. To which is added, a letter to the author, from Mr. John Birch, surgeon, on the subject of medical electricity / by the late George Adams.

  • Adams, George, 1750-1795.
Date:
1799
Catalogue details

Licence: Public Domain Mark

Credit: An essay on electricity : explaining the principles of that useful science, and describing the instruments, contrived either to illustrate the theory, or render the practice entertaining : illustrated with six plates. To which is added, a letter to the author, from Mr. John Birch, surgeon, on the subject of medical electricity / by the late George Adams. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    negative electricity. Though this in many cases holds trae with respect to silk ribbons, yet Mr. Bergman says, that if the ribbon. A, be black, it will never become positive, unless B be black likewise. With pieces of glass the effect is con- trary; for, if they are both equal, the piece. A, which is drawTt across the piece, B, becomes ne- gative; and B, which suffers the greatest friction, becomes positive. Heating by fire produces the same effect as the greater friction. If one piece of glass be thicker than the other, the former be- comes positive, the latter negative. Coloured glass, even when heated, becomes negative, if rubbed with common white glass. If a piece of blue glass is rubbed against a green one, the blue glass becomes strongly positive, &c. Bergman^ Swedish Tran. 1765. The electricities produced by hair and glass rubbed together seem to balance each other, and * are therefore different according to the manner of rubbing and the quality of the hair. Hair of a living animal, or hair newly cut, when rubbed with a glass tube lengthways, is positive; atid here the glass, which suffers the greatest fric- tion, is negative. But, if the glass tube be drawn across the animal’s back, or across a skain of hair newly cut, tlie glass becomes positive. Old dry hair, rubbed bn glass or on living hair, always Uecomes negative; but, if the hair is a little