Gimbals.
A suspension used for ships' compasses and sometimes for other
apparatus. It consists of a ring held by two journals, so as to bc free
to swing in one plane. The compass is swung upon this ring, being placed
concentrically therewith. Its journals are at right angles to those of
the ring. This gives a universal joint by which the compass, weighted
below its line of support, is always kept horizontal.
Fig. 191. COMPASS SUSPENDED IN GIMBALS.
Glass.
A fused mixture of silicates of various oxides. It is of extremely
varied composition and its electric constants vary greatly. Many
determinations of its specific resistance have been made. For flint
glass at 100° C. (212° F.) about (2.06E14) ohms --at 60° C (140° F.)
(1.020E15) (Thomas Gray) is given, while another observer (Beetz) gives
for glass at ordinary temperatures an immeasurably high resistance. It
is therefore a non-conductor of very high order if dry. As a dielectric
the specific inductive capacity of different samples of flint glass is
given as 6.57--6.85--7.4--10.1 (Hopkinson), thus exceeding all other
ordinary dielectrics. The densest glass, other things being equal, has
the highest specific inductive capacity.
Gold.
A metal, one of the elements; symbol Au. c .; atomic weight, 196.8;
equivalent, 65.6; valency, 3; specific gravity 19.5.
It is a conductor of electricity.
Annealed. Hard drawn.
Relative Resistance (Annealed Silver = 1), 1.369 1.393
Specific Resistance, 2.058 2.094
Resistance of a wire at 0° C. (32°F.)
(a) 1 foot long, weighing 1 grain, 57.85 58.84 ohms
(b) 1 foot long, 1/1000 inch thick, 12.38 12.60 "
(c) 1 meter long, weighing 1 gram, .4035 .4104 "
(d) 1 meter long, 1 millimeter thick, .02620 .02668 "
Resistance of a 1 inch cube at 0° C.(32° F.) .8102 .8247
Approximate increase in resistance per 0° C., (1.8° F)
at about 20° C. (68° F.), 0.365 per cent.