198 
THE TELEGRAPH. 
and in order to prevent the sulphate of zinc getting mixed with 
the paper pulp, a thick cloth separator is placed below the paper. 
These cells have too great a resistance to be used for local 
batteries, but they are well suited for using with long lines. 
No others are employed on the Indo-European line between 
London and Teheran. 
The Minotto battery is the one used in British India, and at 
nearly all the stations of the submarine cable companies. It is 
Fig. 133. Fig. 134. 
formed (fig. 134) of a gutta-percha vessel, at the bottom of 
which is placed a disc of copper having a gutta-percha covered 
wire attached to it to form the + electrode. Upon the plate 
of copper crystals of sulphate of copper are placed, and above 
them a separator of porous paper or cloth. Above the 
separator damp sawdust, b, is piled up, and upon this rests the 
zinc z provided with its electrode. This form of battery is 
very portable, and therefore it is preferred for sending to 
distant stations. It remains constant without any special 
care. Its internal resistance is about 20 ohms, when it is in 
good condition. It is always used for testing submarine cable 
at sea, and olten on land also. The advantage of having for 
