1 88 THE SCIENTIFIC PAPERS OF 



could be done by comparing the results obtained by the Trinity 

 House engineers, with the well-known facts as regarded gas light. 

 The electrical machine produced, with 1 HP., 1250 candle power, 

 at the South Foreland. What, then, was the amount of coal used 

 in generating that amount of light ? It would in an average 

 engine be 3 Ibs. of coal. Therefore, 1 Ib. of coal elicited by the 

 electric machine 417 candle power. In lighting by gas 6 cubic 

 feet of gas gave 18 candle power if the gas was fairly good, so 

 that 417 candles would be equal to 139 cubic feet of gas. A 

 ton of coal yielded 10,000 cubic feet of gas, so that 30 Ibs. of 

 coal would represent the 139 cubic feet of gas necessary to furnish 

 the same amount of light afforded by the electric candle with 1 Ib. 

 of coal. There was, therefore, apparently a comparison of 30 to 1 ; 

 but with gas, after allowing for the heating of the retorts, &c., 

 half the weight of fuel might be considered as returned in the 

 form of coke ; therefore 15 Ibs. of fuel were actually consumed in 

 producing the amount of luminous effect that could be obtained 

 in the case of the electric light with 1 Ib. of fuel. He did not 

 say that practical illumination could at once be effected at that 

 enormous difference of cost. The authors of the paper had given 

 the data of actual working results, which were already sufficiently 

 favourable. Hitherto, however, the light had been exhibited on 

 a small scale : but, in order to institute a fair comparison, it 

 should be carried out on a somewhat similar scale to that of gas 

 lighting. He believed in time electric light stations would be 

 established within squares and large blocks of houses. A 

 100 HP. engine would be sufficient to supply conductors for a 

 large number of lights, and they could be increased indefinitely. 



The second question brought forward in the paper was that of 

 the transmission of power, which, although new and untried, was 

 one of considerable interest. By electrical transmission of power, 

 an amount of from 40 to 50 per cent, was recovered at the end 

 of the line. By putting one such machine to work with an ex- 

 penditure of, say 3 HP., a power could be produced and utilised 

 at a distance not exceeding half a mile or a mile, according to 

 the size and length of the conductor, equal to nearly one-half that 

 amount. If at certain stations, 100 HP. were so exerted, it 

 would be possible to distribute over a town power which would 

 be exceedingly convenient and free from the dangers and troubles 



