COST OF ELECTRIC LIGHTING. 243 



under the most favourable conditions, be 2*4 centimes, and 

 under the most unfavourable, 3*4 centimes per hour for each 

 Carcel lamp, which would nearly correspond with the cost of 

 gas at Paris. 



With the new machines the cost is greatly reduced, as the 

 figures given by various engineers for the Gramme machine 

 will show. If this machine is used only where there is a 

 large space to be lighted, ancl where there is a motor so 

 powerful that the addition of one or more machines does 

 not interfere with its regular run for the workshop, the cost of 

 the electric light is surprisingly small. 



"Under these conditions," says Fontaine, "a Gramme ma- 

 chine mounted on a pedestal costs 1,600 francs, a Serrin regu- 

 lator 450 francs, and the price of the conductors is according to 

 their length, and about i or two francs per metre. The carbons 

 of the regulator cost about 2 francs per metre, and their con- 

 sumption is 8 centimetres per hour. Now, 500 hours a year of. 

 lighting, and 4 apparatus in the same establishment, the annual 

 expenses if a steam-engine is used are : 



4,000 kilos, of coal at 35 fr. per ton 



1 66 metres of retort-coke carbons 



Working the machines at o fr. 50 c. per hour 

 .Sinking of 10,000 fr., at 10 per cent, per annum 



Total 



'" If hydraulic power can be used these expenses are reduced 

 to 1,570 francs. 



u For a single lamp we must reckon 30 centimes of mainten- 

 .ance per hour, which increases a little the proportional cost. On 

 the other hand, for 8 lamps the maintenance does not exceed 

 75 centimes, and the proportional price is lessened. Adopting 

 as a basis of calculation 525 francs for each apparatus per year 

 for 500 hours of lighting, we may be certain of being within the 

 mark. 



" With the new Gramme machines (form of 1 877) and the 

 Gauduin carbons, the cost of the unit of light per hour is reduced 

 tby 40 per cent. 



'*' 16 c 



