204 
THE TELEGRAPH. 
bent into a cylindrical shape. It is carefully amalga¬ 
mated, to prevent its rapid solution. A plate of red 
copper, rivetted to the zinc, forms the negative electrode 
of the arrangement. This plan is preferred to the use 
of a screw pressing strongly on the zinc, p is the porous 
vessel, in which a square prismatic block of retort coke is 
placed. The top of this piece of coke is covered with a layer 
of electrolytically deposited copper, to which a strip of red 
copper is fixed. The porous vessel is filled with nitric acid 
diluted with water, and into the stoneware jar containing the 
Fig. 141. Fig. 142. 
zinc, water acidulated with 10 or 12 percent, of sulphuric add 
is poured. 
In the Leclanche battery the outer vessel is square, with a 
neck into which the porous vessel fits rather closely, so as 
to considerably diminish the evaporation (fig. 143). This 
neck has a longitudinal enlargement to allow a rod of zinc to 
pass through it, and liquids to be poured down. The zinc is of 
drawn metal, with an electrode of galvanized iron wire fixed 
into its upper end. The porous vessel is filled with powdered 
retort carbon and peroxide of manganese in equal quantities. 
In the middle of it is a plate of coke, on which a leaden head is 
cast to form the negative electrode of the cell. The outer 
vessel is only half filled with water, and then chloride of 
ammonium is added. 
