Lectures on electricity / by James Ferguson, F.R.S.

  • James Ferguson
Date:
1825
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on electricity / by James Ferguson, F.R.S. Source: Wellcome Collection.

    37/112 (page 31)
    EXPERIMENT VII. Drawing off Streams of Electric Fire. 48. Hang the thin brass-plate X (§ 19,) upon the prime conductor, and darken the room. Then turn the glass globe of the machine by the winch, and hold your knuckles near the edge of the plate ; and you will see streams of fire issuing from the plate to your knuckles, and feel it like a gentle wind. If you move your hand round the edge of the plate, the fire will follow your hand, and come to it. The knuckles, being conductors, draw oft the fire from the electrified plate.18 EXPERIMENT VIII. Dancing of Electrified Bran, Images, fyc. 49. Set the brass-plate Y (§ 19,) directly under the plate X, and about two or three inches from it, as you will soon find by experience what distance is best. Then put a little dry sand, bran, or pollard upon the plate Y. This done, turn the globe by the winch ; and the sand or bran will move up and down with a surpris- ing rapidity between the plate, so that you cannot dis- tinguish the particles, but the whole will look like a white mist. Note 18. Several amusing experiments depend on this property of pointed bodies, to transmit the electric fluid. If a plate of tin be cut into the form of a star, and be supported on its centre by a wire project- ing from the prime conductor, as soon as the wheel of the machine is turned, and this apparatus electrified, a flame will appear at the ex- tremity of every a^gle of the star, which will be very beautiful; and if the star be made to turn swiftly on its centre, an entire circle of fire will be seen in the dark. This experiment will appear very surprising toper- sons unacquainted with electricity, if the operator now and then privately touch the prime conductor, which may easily be managed, as the experi- ment is performed in the dark ; for by this means he may command the appearance or disappearance of the star, or circle of fire, at pleasure.