730 
Proceedings of the Royal Society 
cell greater tlian the legitimate electromotive force of the cell. But it 
is impossible to suppose so high an opposing electromotive force 
being set up as this explanation would require, and there is nothing 
in the chemical reactions of the cell to account for it. I have also 
observed a cell get very hot under the influence of a powerful 
current, no doubt on account of its great resistance. I set to work 
to remove this difficulty in the use of the cell as a secondary battery, 
both chemically and mechanically. To remove it mechanically I 
increased the surface of the copper plate by covering it with 
precipitated copper. This was a great improvement, the resistance 
accumulating with comparative slowness. I found that the nature 
of the precipitated copper had a great effect, and at last got the 
best results by the reduction of a paste of cuprous chloride covering 
the copper plate. I reduced it by replacing the other copper plate 
with a zinc plate, and running down the cell thus formed. A firm 
spongy surface of copper was thus formed, usually red in colour. 
A still further improvement was made by covering this copper 
surface with a sheet of copper gauze, the copper gauze being soldered 
by wires to the copper plate. The purpose of this gauze was to 
produce two surfaces of action, one on each side of the precipitated 
copper, also to steady the current flowing from the cell when it 
was charged, by preventing its internal resistance from changing so 
much as it would otherwise have done. I have curves showing 
the gradual improvement in charging capacity of the cell. These 
curves were plotted after each experiment. I attach great 
importance to this surface of wire gauze, both in the primary and in 
the secondary cell. 
The way I propose to use it in the primary cell is as follows : — 
Let us suppose a primary cell consisting of a jar containing cuprous 
chloride, with a copper plate round the inside as the one pole, and 
with a small porous pot in the centre containing a zinc rod and 
chloride of zinc solution. The resistance of this cell would be con- 
siderable at first, and as the cuprous chloride was gradually reduced 
from the copper plate in towards the centre, leaving behind it 
copper, the resistance of the cell would become less, and in this way 
a gradually increasing current would be supplied. But if we had 
a cylinder of copper gauze surrounding the porous pot, and in 
metallic connection with the copper plate, it would form another 
