142 THE NORTHERN MICROSCOPIST. 

the production of light. But the vapours of hypo-nitric acid, which 
it gives off together with the difficulties of charging it, are a great 
bar to its introduction, save in the open air, or in a laboratory where 
little account is taken of these inconveniences. The Bunsen bat- 
tery, therefore, as arranged by the German chemist cannot be 
recommended to micrographers, but there is now a very good 
modification of it, which not only does away with almost all the 
above mentioned inconveniences, but also allows the production of 
the light at a price much less than when the ordinary Bunsen 
battery is used. It is that contrived by M. Tommasi, and is manu- 
fuctured by the Societé universelle d’electricité Tommast, at Paris. 
This battery is mounted in a very simple manner upon a kind of 
wooden trestle, and is composed of fifty cells, of which each one 
comprises :— 
1. An exterior stoneware jar. 
2. A porous jar containing another vessel of glass, in the bottom 
of which a hole is so contrived as to facilitate the flow of the liquid 
coming in to supply the place of that which has become useless, 
and which gradually escapes by the pores of the jar. 
The glass bottle, and consequently the porous jar, are filled with 
a mixture formed with two parts of a saturated aqueous solution of 
nitrate of soda and three parts of sulphuric acid solution, acidulated 
to 45° B. 
Besides these a carbon conductor is plunged into the porous jar. 
As the exhausted liquid flows away by the pores of the porous 
jar it is replaced as we have just said by the unused supply in the 
glass bottle. 
The exterior jar encloses a copper wire support, having on its 
upper part a platinum claw intended to grasp the carbon conductor 
of the next cell. 
About the porous jar and in the exterior one are arranged four 
zinc rings, one centimetre thick, which rest upon the support we 
have just mentioned. 
The exterior jar is filled to the brim with water acidulated to 
4 p.c. with sulphuric acid, and which is introduced into it in the 
manner now to be described. 
The exterior jars communicate with each other in series of five, 
by means of glass tubes provided with caoutchouc coverings and 
placed at the lower part of each jar. By means of this arrange- 
ment the charging of the battery is accomplished in the twinkling 
of an eye by the aid of ten taps mounted upon two leaden rails set 
in communication with the central box, previously filled with 
acidulated water. 
To charge the battery therefore it is only necessary to open the 
ten taps, of which each serves a series of five cells. ‘The battery 
is thus prepared for operation instantaneously. 
