1879.] 
87 
L. Schwendler —On Electric Light Measurements. 
practical difficulties which still remain to be solved ; but, at the same time, 
gas companies should be aware that they have a formidable rival in the 
field, and bestir themselves to maintain the lead they hold by improving 
their own means of illumination and extending its application. 
Precis of the Report on the results obtained by the Electric Light Experi¬ 
ments instituted on behalf of the Board of Directors of the East 
Indian Railway Company.—By Louis Schwendlee, Superintendent 
Electrician of Government Telegraphs in India (on special duty in 
England), dated lsi November, 1878. 
Results obtained .—The questions which I set myself to answer by 
direct experiment were :— 
I.—Quantity op Light pee unit op powee, unit op speed, 
AND UNIT OP MONEY (PIEST OUTLAY). 
To solve this question I have tried four different Dynamo-electric 
Machines producing the electric current in one direction, viz.— 
A Medium size, 
13 Small, 
Dynamo-electric Machines 
as supplied by Messrs. Siemens, Brothers, of London (construction :—Sie¬ 
mens ; system :—Hefner von Alteneck). 
Dynamo-electric Machine C, workshop pattern, as supplied by Messrs. 
Soutter & Lemonnier, of Paris (construction :—Gramme). 
Dynamo-electric Machine D, with two sets of brushes, as supplied by 
the British Telegraph Manufactory (construction :—Gramme). 
Careful, severe, and long-extended trials, during the time of my ex¬ 
periments, have established that these four machines are all sufficiently 
practical for the production of the electric light, but that, as a rule, the 
statements of their actual efficiency were not found to be in conformity 
with the results obtained from my own experiments. The quantity of 
light produced by these dynamo-electric machines had been overrated, 
and the amount of power consumed underrated. 
This discrepancy between my results and those of others is probably 
to be explained by the difficulties which stand in the way of executing 
trustworthy photometric measurements. 
But, notwithstanding this, I find that the unit of light as produced in 
the electric arc ( disintegration ) by any of the four dynamo-electric ma¬ 
chines is at least fifty times cheaper than the unit of light as produced by 
combustion, considering the expenditure of power only. 
This represents an enormous engineering margin in favour of the 
electric light. 
