. . . |2s.6d.| Nil | Nil | 285 |
| | Large glow . . . . |2s.6d.| " | " | 360 |
| Electricity| | [5] | | | |
| | Tantalum . . . . . |7s.6d.| " | " | 172 |
| | Osram . . . . . . | 6s. | " | " | 96 |
|____________|____________________|______|_________|__________|_________|
[Footnote 1: Interest and depreciation charges on generating and
purifying plant = 0.15 penny. Purifying material and burner renewals =
0.05 penny.]
[Footnote 2: Mantle renewals as for coal-gas.]
[Footnote 3: Renewals of wicks and chimneys = 0.02 penny.]
[Footnote 4: Renewals and mantles (and chimneys) at contract rate of 3s.
per burner per annum.]
[Footnote 5: Renewals of lamps and fuses, at price indicated per lamp per
annum.]
The conventional method of making pecuniary comparisons between different
sources of artificial light consists in simply calculating the cost of
developing a certain number of candle-hours of light--_i.e._, a
certain amount of standard candle-power for a given number of hours--on
the assumption that as many separate sources of light are employed as may
be required to bring the combined illuminating power up to the total
amount wanted.
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