246 ELECTRIC LIGHTING. 



"Although under certain circumstances these two agents un- 

 doubtedly come into competition, they have two separate fields. 

 Hitherto gas been generally employed for lighting spaces of both 

 large and small dimensions, because a better source of light for 

 large spaces has not been procurable with economy. But for 

 lighting large spaces that are not subdivided by opaque objects 

 or screens, it is a want of economy to employ gas. If, in fact, a 

 gasworks were to be constructed simply for lighting large spaces, 

 as does occur in some extensive works, the disbursement neces- 

 sary to establish even a small gasworks would, compared with 

 that necessary to establish the electric light, be a considerable 

 multiple of the latter. Assuming light-power proportional to- 

 horse-power expended (although it increases at a greater rate),. 

 100 horse-power would give 150,000 candles light ; if this be dis- 

 tributed from three points, the cost of each lamp per hour would 

 not be more than js. 6d., or i 2s. 6d. per hour for the three, 

 each light centre giving an illumination which would enable 

 small print to be read at a distance of a i mile from the light. 

 A burner giving the light of 20 cafrdles consumes 6 cubic feet of 

 gas per hour, which may be manufactured at a cost of 2s. per 

 1,000 cubic feet. This gives 7,500 burners' light only, and 45,000 

 cubic feet of gas at a cost of 4. 105-. per hour, a ratio of 4 to i 

 in favour of electric lighting. Electric lighting, where adopted, 

 has been found to be generally more economical than gas light- 

 ing, but the economical ratios differ greatly, and are dependent 

 chiefly upon the price of gas and the motor power employed. 

 For large spaces the cost of electric lighting is about one-fourth, 

 or even one-fifth of that of gas lighting, when steam has been 

 used as a power, and wear and tear are reckoned. With a gas 

 engine as motor, the ratio has only been as I to 3, the greatest 

 economy having been with a turbine as motor. At 'Dieu's work- 

 shops at Davours the cost per hour for gas is 2s. o 632^. against 

 i s. j.2d. for electric lighting. Ducommun . finds, taking into 

 account wear and tear and interest, that gas costs 2*25 times 

 more than the electric light, which ratio increases to 7'i5 when 

 wear and tear and interest are left out of consideration. At 

 Siemens Brothers' Telegraph Works the cable shops are im- 

 perfectly lighted with 120 gas-burners. Each of these burners 

 consumes 6 cubic feet per hour, at a cost of $s. <)d. per 1,000 

 cubic feet The cost of fixing gas-pipes, including cost of pipes, 



