

148 THE NORTHERN MICROSCOPIST. 


from M. F. Carré and Sir W. Thomson improvements which ren- 
dered its internal resistance very small. It was, therefore, already 
shewn that batteries of this kind, without exceeding suitable dimen- 
sions, gave effects of quantity; little was wanting for them to 
become, by the aid of accumulators, convenient generators of 
electricity for laboratories and domestic use. 
It is this little that we have supplied in simplifying the service 
of the battery, and reducing, within certain limits, its daily expense. 
The receiver is of copper, and acts the part of the positive elec- 
trode, the zinc, of rectangular form, is enveloped by a porous case 
of paper-parchment, made in the same way as those of our former 
battery, but much narrower. The zinc fills this porous case almost 
entirely, and this case we shall call the partitioning. A fine canvas 
sewn underneath protects the paper. 
A zinc thus partitioned off, and steeping in a sulphate of copper 
solution, forms, with the sides of the receiver, a constant couple 
with little resistance. 
In the narrow compartment, which holds the zinc, sulphate of 
zinc is formed at first by local action, at the expense of the elec- 
trode and of a small quantity of sulphate of copper which reaches 
it through the partition. The couple places itself therefore in its 
normal condition of operation. The excess of sulphate of zinc 
which eventually finds its way out at the fastening of the circuit 
will be diffused towards the outer compartment. ‘This action of 
osmose is sufficiently rapid, favoured as it is by the great solubility 
of the salt, and by a phenomena of transport effected from the 
negative to the positive in the interior of the couple by the current 
itself. Thus the osmose becomes powerful just when it becomes 
necessary that it should be so. 
We have not, therefore, to occupy ourselves about the zinc com- 
partment ; the service of the apparatus is practically that of a battery 
with a single liquid. 
Again, the renewing of the sulphate of copper is a work of the 
most simple kind. It consists in lowering the caoutchouc tube 
with which each couple of the battery is provided, to allow a por- 
tion of the exhausted liquor to flow away, then raising these tubes 
again to add ordinary water, and putting a previously weighed 
charge of copper sulphate into a wicker case suspended in the 
upper part of the receiver. 
To diminish the interior resistance we can throw into the couple 
a few grains of a conductive mixture, composed of several neutral 
or acid salts, which are soluble and very cheap, such as chlorides 
and sulphates of potassium and sodium, sulphate of ammonia, 
nitrate and bisulphate of soda, &c. 
Once a month the battery is taken down to change the enclosed 
zincs and to collect the reduced copper, which is deposited in thick 

