| Price for electric light. | Equivalent price for gas of equal light. | ||||||
|---|---|---|---|---|---|---|---|
| s. | d. | s. | d. | ||||
| 1 | 0 |  | per Board |  | 6 | 10 | per 1000 cubic feet. |
| 0 | 9 | of | 5 | 1½ | ”” | ||
| 0 | 7¼ | Trade | 4 | 2 | ”” | ||
| 0 | 6 | Unit. | 3 | 5 | ”” | ||
Comparison of Cost of Gas and Electricity.
These prices, of course, include the manufacturer’s profit as well as the loss in transmission through the mains and expenses of connecting up to the consumer. The actual manufacturing cost of a station maintaining 10,000 lights should not be more than 3d. per Unit, or equivalent to gas at 1s. 8½d. per 1000 cubic feet.[2]
As petroleum lamps are used for the street lighting of many foreign and colonial towns, the question arises, “Will it pay to substitute the electric light?” Comparing the light given by a kerosene or petroleum lamp with that from the incandescent electric lamp, the cost is greatly in favour of oil; and, in fact, where the price of kerosene is under 1s. per gallon, electricity cannot compete if labour is cheap. On the other hand, the trimming, lighting, and keeping in order of a number of lamps scattered over a large area greatly augments the working cost, to which must be added the breakages of chimneys, expense of wicks, also the danger of fire. It is the safety of electricity which has caused it to supplant oil both for public and private lighting in American cities; even where the price of kerosene is not more than 6d. per gallon there is a demand for the electric light, which is by far the dearer illuminant, after making a liberal allowance for labour in cleaning, filling, and lighting the oil lamp, also for depreciation of the burners.
Arc and Incandescent or Glow Lighting.
Fig. 3.
Electric lighting can be obtained by means of arc or incandescent lamps. The arc light is now well understood to be caused by the extremely high temperature of the end of one or both the carbon electrodes. The voltaic arc, [Fig. 3], is formed by the minute particles of carbon in a high state of combustion which the current appears to break off and carry from one electrode to the other, the light, however, being mainly due to the incandescence of the crater shown in [Fig. 3] on the upper carbon. In the incandescent or glow lamp light is produced by the passage of a current of electricity through a continuous fine thread or filament of carbon which becomes white-hot, the destruction of the filament being prevented through its enclosure in a glass bulb from which the air is exhausted. Figs. 4 and 5.
The first method is suitable for the lighting of streets where a high-class illumination is required; also will be wanted for the external lighting of shops, public-houses, and places of amusement, so that arrangements must be made for arc lighting. The usual plan is to charge at the same rate per Unit by meter as the incandescent lamps, but to make an additional charge of 5s. to 7s. 6d. per lamp per quarter for rent, and a further charge of 3s. per week for cleaning and trimming.