ELECTRIC LIGHT APPLIED TO MICROSCOPICAL RESEARCH. I4I 


THE ELECTRIC LIGHT APPLIED TO 
MICKOSCOPICAI RE SEA Ee 
By Dr. HENRI Van Heurcx. 
A Paper read before the Microscopical Society of Belgium. 
|i spite of the perfection of homogeneous immersion objectives, 
which easily shew up fine details, it often happens that the com- 
plete study of diatoms, especially of the more minute forms, is very 
wearisome, both on account of the difficulty experienced in resolv- 
ing the striz, and the almost impossibility of counting them with 
the aid of only a medium magnification. 
Recourse must then be had to high magnification, sometimes 
even to the mono-chromatic light, but the sun by its non-appear- 
ance often renders the work impossible, especially in winter. 
For some time past we had been thinking of the electric light for 
the illumination of the microscope, but only thought of obtaining 
the mono-chromatic light. . Our recent experience, however, has 
shewn us that the incandescent light fulfils par excellence the 
demands of the micrographer. 
It is proposed, then, in the present article to examine into the 
means that the micrographer can employ for the utilization of the 
electric light, and the advantages to be obtained from its employ- 
ment. 
I. PRODUCTION OF THE ELECTRICITY. 
Everything at present goes to shew that in a not far off future the 
inhabitants of large towns will be able to receive electricity in their 
houses by means of a subterranean or aérial communication with 
the place where it is generated. It would therefore be unnecessary 
for us to occupy ourselves with the production of electricity, were 
it not for those dwelling in the country or in small centres who 
would wish to avail themselves of the advantages offered by 
electrical illumination. 
There are at present two means of producing electricity ; 
dynamo-electric machines and batteries. Dynamo-electric machines, 
of which the most common is that invented by our countryman, 
-M. Gramme, produce electricity at a cheap rate. Unfortunately 
they are costly themselves and require a gas or steam motor much 
more costly still, which brings the total cost to a considerable sum. 
A micrographer will therefore seldom have recourse to one of these 
for observations at irregular intervals, when a small battery will 
enable him to obtain the desired illumination at a slightly higher 
cost but almost without trouble. : 
The number of forms of batteries existing at the present day is 
very considerable, but as yet Bunsen’s is unrivalled, especially for 
