Frying.
A term applied to a noise sometimes produced in a voltaic arc due to too
close approach of the carbons to each other. It has been suggested that
it may be due to volatilization of the carbon. (Elihu Thomson.)
Fulgurite.
An irregular and tubular mass of vitrified quartz, believed to be formed
by melting under the lightning stroke.
Fig. 175. CRUCIBLE, ELECTRIC.
Furnace, Electric.
A furnace in which the heat is produced by the electric current. It has
hitherto been practically used only in the extraction of aluminum and
silicium from their ores. The general principle involves the formation
of an arc between carbon electrodes. The substances to be treated are
exposed to the heat thus produced. Sometimes the substances in the arc
form imperfect conductors, and incandescence takes a part in the action.
Sometimes the substances are merely dropped through the arc.
[Transcriber's note: Silicium is silicon.]
Fuse Board.
A tablet on which a number of safety fuses are mounted. Slate is
excellent material for the tablet, as it is incombustible, and is easily
drilled and worked.
Fuse Box.
A box containing a safety fuse. Porcelain is an excellent material for
its base. No combustible material should enter into its composition.
Fuse, Cockburn.
A safety fuse or cut off which consists of a wire of pure tin running
from terminal to terminal, to whose centre a leaden ball is secured by
being cast into position. The connection with the terminals is made by
rings at the ends of the wire through which the terminal screws are
passed and screwed home. When the tin softens under too heavy a current
the weight of the shot pulls it apart.
Fig. 176 COCKBURN SAFETY FUSE.