
150 THE NORTHERN MICROSCOPIST. 


light of any degree of brilliancy, working without an accumulator. 
Some valuable notes in this direction by Dr. J. M. H. Munro may 
be found in the present number.—Ep. 

BATTERY POWER FOR SWAN LAMPS. 
By Dr. MuNRo. 
(From the Mechanical World.) 
OR the benefit of those of your readers who wish to experiment 
with or exhibit the electric light, and who are yet unable to 
understand the jargon of volts, ohms, and amperes, I will relate 
my own experience as to the battery power necessary. I feel sure 
from the number of queries that appear on the subject, and the 
' discordant replies elicited, that many will be glad of the informa- 
tion. A few days ago I wished to exhibit the electric light, and 
had at my disposal forty Grove cells of the usual size, three Swan 
lamps of 25 to 50 candle power (sold at first at 25s. each, and 
lately at 12s. 6d. each), and a Serrin arc lamp, in which the 
approach of the carbons is regulated by clockwork. I was assured 
by the local vendor of one of the Swan lamps that fifteen Grove 
cells were guaranteed sufficient to work the same. The dealer 
from whom I procured the loan of the other two Swan lamps, 
however, stated that less than 4o cells would give an unsatisfactory 
result, even with one lamp, but that 40 cells would be quite 
sufficient for one, two, or three lamps. I first tried one Swan lamp 
with 10 Grove cells, with no visible result ; 15 cells gave a red glow 
with one lamp, which diminished to a very dull red when three 
lamps were tried together; 25 cells gave a fairly good light with 
one Swan lamp, considerably diminished when two or three were 
brought into circuit; 40 cells produced a light of wonderful brilli- 
ance and steadiness with one lamp (quite equal to any incandescent 
light I have seen produced from the currents of a dynamo machine), 
and with two or three lamps in circuit the result was perfectly 
satisfactory, although there was a distinct falling off in the light 
from each lamp taken separately. In all these cases the battery 
was coupled in simple series (¢.e., intensity fashion), and the lamps 
when arranged in multiple arc (¢.e., each lamp was independently 
connected with the two poles of the battery). When the Serrin 
lamp was also introduced into the arrangement (being also con- 
nected independently with each pole of the battery) the 40 cells 
were found sufficient to give a brilliant light, when the carbons 
were approached to the proper distance, the three Swan lamps 
simultaneously falling off to a barely visible glow. By simply sepa- 
Ti 

