In the cut P is the base board, M is a glass covered case containing the
magnetic needle, and sliding along the base board, being guided by the
central groove, C, is the coil. Between the coil and the needle is the
arched or bent controlling magnet. The long twisted connecting wires are
seen on the right hand.
Galvano-plastics.
The deposition of metals by electrolysis, a disused term replaced
by electro-deposition, electroplating, and electro-metallurgy.
Galvano-puncture.
An operation in medical electricity. (See Electro-puncture.)
Galvanoscope.
An instrument, generally of the galvanometer type, used for ascertaining
whether a current is flowing or not. Any galvanoscope, when calibrated,
if susceptible thereof, becomes a galvanometer.
Gas, Electrolytic.
Gas produced by the decomposition, generally of water, by electrolysis.
It may be hydrogen or oxygen, or a mixture of the two, according to how
it is collected. (See Gases, Mixed.)
Gases, Mixed.
The mixture of approximately one volume of oxygen and two volumes of
hydrogen collected in the eudiometer of a gas voltameter or other
electrolytic apparatus.
Gassing.
The evolution of gas from the plates of a storage battery in the
charging process, due to too high voltage in the circuit of the charging
dynamo.
Gastroscope.
An apparatus for illuminating by an incandescent lamp the interior of
the stomach, and with prisms to refract the rays of light so that the
part can be seen. The stomach is inflated with air, if desirable, to
give a better view. An incandescent platinum spiral in a water jacket
has been employed for the illumination.
Gassiot's Cascade.
A goblet lined for half its interior surface with tinfoil. It is placed
in the receiver of an air pump from the top of whose bell a conductor
descends into it, not touching the foil. On producing a good
rarefaction, and discharging high tension electricity from between the
conductor just mentioned and the metal of the machine, a luminous effect
is produced, as if the electricity, pale blue in color, was overflowing
the goblet.
Gauss.
A name suggested for unit intensity of magnetic field. Sylvanus P.
Thomson proposed for its value the intensity of a field of 1E8 C. G. S.
electro-magnetic units. J. A. Fleming proposed the strength of field
which would develop one volt potential difference in a wire 1E6
centimeters long, moving through such field with a velocity of one
centimeter per second. This is one hundred times greater than Thomson's
standard. Sir William Thomson suggested the intensity of field produced
by a current of one ampere at a distance of one centimeter
The gauss is not used to any extent; practical calculations are based on
electro-magnetic lines of force.