i879-1 
The Electric Light for India, 
303 
VII. THE ELECTRIC LIGHT FOR INDIA. 
® N the report on the results obtained by the eleCtric light 
experiments, instituted on behalf of the Board of 
w Directors of the East Indian Railway Company, Mr. 
Louis Schwendler states that in endeavouring to determine 
the quantity of light per unit of power, unit of speed, and 
unit of money, he tried four different dynamo-eleCtric ma- 
chines producing the eleCtric current in one direction, viz., a 
medium and a small-sized Siemens (Hefner von Alteneck) 
dynamo-eleCtric machines ; a dynamo-eleCtric machine, 
workshop pattern, as supplied by Messrs. Soutter and 
Lemonnier, of Paris ; and a dynamo-eleCtric machine with 
two sets of brushes, as supplied by the British Telegraph 
Manufactory. The trials have established that these four 
machines are all sufficiently practical for the production of 
the eleCtric light, and that the unit of light as produced in 
the eleCtric arc by any of the four dynamo-eleCtric machines 
is at least fifty times cheaper than the unit of light as pro- 
duced by combustion, considering the expenditure of power 
only. This represents an enormous engineering margin in 
favour of the eleCtric light. 
The Siemens medium dynamo-eleCtric machine, however, 
gives about double the quantity of light of any of the other 
three machines, and only about half as much power is ex- 
pended to produce the unit of light. This favourable result 
is principally due to the comparatively small internal resist- 
ance of the machine, and to its low speed. 
For use in India Mr. Schwendler proposes several altera- 
tions in the machine. 
With regard to lamps, Mr. Schwendler for practical use 
prefers the Serrin lamp, with the following alterations, which 
his own experiments have suggested : — 
1. All parts of the lamp, including clockwork, &c., to be 
made of gun-metal. No steel or iron is to be used except 
in the eleCtro-magnet and its armature. 
2. The carbons may be of any shape — round, triangular, 
or square. The carbon-holders, constructed as in the 
Siemens lamp, should be sufficiently large to hold a round 
carbon of 18 m.m. diameter. With 18 m.m. carbons the 
lamp should burn eight hours. 
3. The screw for regulating the tension of the spring or 
springs which aCt in opposition to the magnetism of the 
VOL. ix. (n.s.) x 
