2o8 
the telegraph. 
ness, thus, A, then a portion only of the current will pass the 
upper point, and the rest will take the shorter path, and the 
total amount passing will also be greater than before. If the 
cross-piece forms an equilateral triangle w T ith the other parts, 
tr.en that cross-piece will convey two-thirds of the total current, 
and only one-third will pass through the vertex. This is the 
principle of derived currents or “ shunts.” 
A single voltaic cell being usually incapable of producing the 
required effects, it is necessary to connect several cells in order 
to obtain the desired results, and the effects will vary according 
