Volume 2

A manual of electricity, magnetism, and meteorology / By Dionysius Lardner.

  • Lardner, Dionysius, 1793-1859.
Date:
[1841-44]
Catalogue details

Licence: Public Domain Mark

Credit: A manual of electricity, magnetism, and meteorology / By Dionysius Lardner. Source: Wellcome Collection.

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    same manner as the slips of gold leaf in Bennett’s elec- troscope. The central wire passing through the small glass tube Bis attached above to the interior of a metal cap D, placed over the cylinder, which protects the upper part of the tube B when the electroscope is exposed to rain. The penetration of moisture to the interior of the apparatus is further prevented by coating the cylinder with wax or varnish. Cavallo’s Portable Electroscope. (252.) This instrument, represented in fig. 71., consists of a small glass tube A B, 3ths of an inch in diameter, and 34 inches in length ; C is a cork inserted in the lower end of the tube, so formed that either end of it may enter the tube. To this cork are attached two silver wires, bearing at their extremities delicate cones of cork or pith. In jig. 70. the wires are seen deposited in the glass tube as in a case, the instrument not being in use. In fig.'71. the cork is reversed, and the wires Fig. 70. Pig. (i. Fig. 72. presented downwards, the cones being represented as when similarly electrified. The glass tube forms a handle for the instrument, and is varnished throughout