Electric Lighting. 105 



amusement, churches, and large establishments, whilst 

 nearly every modern steamship has been, or is being, fitted 

 up with one of the systems. 



With respect to the economy of the incandescent lamp, 

 I think it can be shown that even at the present time the 

 cost of producing an equal amount of illumination will not 

 exceed that of gas. 



A ton of coal will, I believe, produce 10,000 cubic feet of 

 gas — enough to supply 2000 good gas burners for one hour. 

 A ton of coal burnt in the steam-engine will produce 

 748 horse-power and will support 74G0 incandescent lamps 

 of the same power as the gas burner for the same period of 

 time. I have only estimated the horse-power at 3 lbs. of 

 coal per hour, but in an extensive system of lighting to 

 take the place of gas the amount of coal used per horse- 

 power would not be so much. I think on board some of 

 the large, steamers from 1J to 2 lbs. of coal per horse power 

 per hour is all that is used ; but, as in the manufacture of 

 gas the residue of the coal yields products of great value. 

 I have quoted the larger amount as a set off. 



The cost of manufacture, wear and tear, &c, should not 

 be more in the one case than the other ; whilst the distribu- 

 tion would be in favour of the electric lamp ; whilst the 

 cost of renewals would not amount to anything like the 

 difference shown to exist between the two systems. 



Taking another example. Twenty-five cubic feet of gas 

 will produce one horse-power in a gas-engine for one hour, 

 and thus support ten incandescent lamps ; whilst the same 

 amount of gas burnt would only suffice for five burners of 

 equal illuminating power. I have not in this paper treated 

 on the subject of secondary batteries or accumulators, 

 neither having spare time to make any experiments in this 

 direction, nor information of a reliable nature to show that 

 their use in electric lighting has been extended beyond the 

 lecture-room or for experimental work. 



