of Edinburgh, Session 1881 - 82 . 731 
surface of action, and would keep down the resistance of the cell 
from the first. 
« 
I tried to reduce the accumulation of resistance chemically by 
introducing small quantities of various zinc salts. I found nitrate 
of zinc had a wonderful effect in preventing an accumulation of 
resistance though put into the cell in very small quantities. I 
suppose the nitric acid set free on the coj>per surface kept it clean 
from the skin of cuprous chloride, to which the accumulation of 
resistance is no doubt due. Unfortunately it seems to demoralise 
the cell. It is impossible to get the charge put into the cell properly 
and entirely returned. Why this should be I do not know. When 
I found the introduction of the nitrate of no practical use, I examined 
no further into its action. I have therefore had to be content 
with the improvement produced by the porous copper and the wire 
gauze. When the resistance has increased to such an extent as to 
cause a serious waste of the charging current, I consider the cell as 
fully charged. And I would here say, that in secondary batteries as 
at present designed, one of two things seems to be inevitable, — gas 
is given off, or resistance accumulates. 
In the Plants cell the peroxide of lead formed is a conductor ; 
consequently, when the surface exposed is nearly all oxidised, gas is 
given off the oxidised surface ; to the modification of the Plants cell 
by M. Faure the same remarks apply. In my cell the substance 
formed is a non-conductor ; no gas is given off, there is not 
even a smell of chlorine ; but as the surface exposed is converted 
into cuprous chloride, resistance accumulates in the cell. These 
secondary batteries may simply be regarded as polarised plates, the 
amount of polarisation depending on the surface exposed. I am 
afraid, therefore, that it will be very difficult to store a large amount 
of energy in a cell of small surface and weight. The storage in the 
cells invented so far is miserably small, and mine is no better than 
the rest in this respect. 
Another difficulty in this battery has been depositing the zinc 
successfully. It has a tendency to form bunches of crystals, which 
reach across the cell to the copper plate, and form metallic connec- 
tion therewith. The charging current should not be too powerful, 
though a current of three or four times the EMF of the cell 
may be used, and it should be stopped when the resistance becomes 
