86 
L. Schwendler— On Electric Light Measurements. [March, 
trie light is constituted by the practical necessity that lamps, of what¬ 
ever construction they may be, have a resistance inherent to their nature 
in addition to the resistance of the arc. For instance, in an ordinary lamp 
with an electromagnet, the resistance of the lamp consists of the resistance 
of the electromagnet plus the resistance of the two electrodes when metal¬ 
lically closed. This resistance, although small, is by no means nil, and 
cannot be neglected against the resistance of the arc, especially when 
strong currents are used. In other words, when producing the electric 
light in n points instead of one point, we are unable to fulfil practically 
the condition, that the sum of the resistances of the n arcs is equal to 
the resistance of one arc to have the same current, i. e., the former must 
be made smaller than the latter on account of practical construction-reasons. 
We may therefore sum up as follows : The economical solution of the 
division of the electric light is theoretically quite possible, but practically 
difficult to obtain. The division can never become unlimited, but ingeni¬ 
ous inventors may nevertheless solve the problem practically. 
Any attempt by inventors to solve the question is therefore perfectly 
legitimate. If their attempt cannot lead to a perfect solution, they may 
nevertheless do so -approximately, and by it tend towards real progress in 
illumination, inasmuch as by their attempts the electric light may pro¬ 
bably become more and more a successful general rival to gas, which at 
present it certainly is not. 
Before I conclude, I must briefly advert to a paper on “ the Electric 
Light” by Mr. W. H. Preece, published in the Philosophical Magazine 
for January 1879, in which the author believes that he has demonstrated 
from dynamical considerations that the division of the electric light is 
impossible. This it certainly is under the conditions introduced by Mr. 
l’reece, viz., that the resistance of each voltaic arc, or each incandescent 
wire, is maintained constant. But it is unfair to the electric light to 
introduce this condition, especially as it does not at all represent the 
question at issue. 
When a number of lights are connected in series, the resistance of 
each must be diminished, and when a number of lights are joined parallel, 
the resistance of each must bo increased, in proportion to their number, 
so as to maintain the total external resistance constant. If Mr. Preece 
will introduce this condition into his equations he will find that theo¬ 
retically the division of the electric light is quite possible, i. e., that, 
theoretically, however the lights be arranged, the unit of light will always 
be produced by the same expenditure of energy. Inventors should not 
therefore be down-hearted. On the other hand, investors in gas need not 
hasten to get rid of their shares, for there are many questions involving 
