549 
iS73J 
Notices of Books. 
Thus under the most favourable conditions the Gramme ma- 
chine light is 300 times less expensive than the light of wax 
candles. It must be borne in mind, however, that interest and 
wear and tear ought to be charged upon the machinery. 
An exact comparison of the relative cost of gas and electric 
lighting is given in the following tables for a spinning-mill of 
800 looms. 
First, in the case of the gas-lighting 
Number of burners 415 
Number of hours of night-work per year 500 
Cost of introducing gas 12,000 francs. 
Price of cubic metre of gas 0*25 franc. 
Cost of gas per year 5486-85 francs. 
Interest 12,000 francs, at 10 per cent... 1200*00 ,, 
Maintenance of apparatus and contin- 
gencies 263*00 ,, 
Total cost of gas-lighting per year 6950*10 ,, 
The corresponding electric lighting requires : — 
Six Gramme machines, at 1500 francs ... 9000 francs. 
Six regulators of 300 burners, at 450 frs. 2700 ,, 
Wires and mounting 1300 ,, 
Twelve horse-power steam motor 8000 ,, 
Total cost of apparatus ... ... ... 21,000 ,, 
Working expenses : — 
Consumption of eledtric carbons, 
240 metres, at 2*5 francs 
Consumption of coal, 10 tonnes, at 30 frs. 
Interest on 21,000 francs, at 10 per cent 
Annual maintenance and contingencies... 
600 francs. 
300 
) > 
2100 
>> 
1600 
> 1 
Total cost of eledtric lighting per year 4600 ,, 
“ The eledtric light in this case costs annually 33 per cent less 
than that by gas, gives six times more light, and suppresses all 
danger of fire.” 
The light emitted by Geissler’s tubes has been found to be of 
such slight intensity that they are pradtically useless even for 
powder-mills and gunpowder-works. The divisibility of the 
eledtric light, as employed by Jablochkoff in 1877, will appa- 
rently lead to a greater introdudtiion of the use of this kind of 
light. “ By the term ‘ divisibility of the eledtric light ’ we do 
not mean the production of several intense lights by means of 
one machine or battery, but simply the maintaining of a few 
small luminous centres, each equal to 1 to 15 Carcel burners.” 
