The number of lights required to illuminate any room would vary very much, according to the style of decoration and position of the lamps. As a rule, a similar number of glow lamps are required as there would be gas burners. The former give a much higher standard of illumination, which, curiously enough, is generally expected with electric lighting on account of the purity of the atmosphere when the full light is being used, which is not the case with gas.
One 16 candle-power lamp will light an area of about 8 feet in diameter at 8 feet above ground; in ordinary situations allow, one lamp for 38 square feet.
Arc Lighting of Works.
External.—56. 2,000 CP. arc lights will illuminate 160,000 square yards, or one for each 2,800 square yards.
Internal.—43. 2,000 CP. arc lights will illuminate 31,500 square yards, or one for each 730 square yards.
Approximate Cost of Electric Light, Museum.
| Arc lighting, | ²⁄₅ gas; | with interest, | ²⁄₃. |
| Incandescent, | ²⁄₃ gas; | with interest, | ⁴⁄₃. |
Motive Power.
Compound engine 2 lbs. of coal per indicated horse-power per hour.