_£ s. d._
10- to 16-candle-power 0 16 0 per annum.
25- ” ” 1 0 0 ”
50- ” ” 1 10 0 ”
100- ” ” 2 0 0 ”
A discount is allowed off this meter charge, varying with the number of
hours the light is used in the year.
The cost of gas is about 4_s._ 9_d._ per 1,000 cubic feet, so the
electric light is slightly the dearer illuminant.
The Aron meter, Fig. 19, is usually employed as the recorder of the
electricity consumed. It consists of two pendulums, controlling two
distinct clockwork gears. One oscillates at a regular speed, but the
other has a permanent magnet, instead of a weight, and is variable in
speed. The entire current passes through the solenoid, which is
underneath the pendulum, with the magnet; the difference in speed
between the standard and variable clocks is given in direct
ampère-hours by a counter-gearing similar to the index of a gas-meter.
An electro-magnet starts each pendulum when the current begins to flow,
and immediately it ceases, two detents come into operation and hold the
pendulums stationary.
[Illustration: FIG. 19.]