Meters are charged as follows:—
| £ | 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 4s. 9d. 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.
Fig. 19.