CHAPTER IV. 
SOURCES OF ELECTRICITY. 
Danielfs, Thomson’s, Siemens’ and Minotto’s Batteries—Thomson’s Trough 
Battery ; Callaud’s, Meidinger’s, Bunsen’s, Grove’s and Leclanche’s 
Batteries — English Telegraph Battery — Arrangement of Batteries — 
Electro-magnets. 
The supply of electricity required for working telegraph 
apparatus may be obtained in several ways. Ohm reasoned 
on electricity from its analogy with heat passing along a bar 
heated at one end and cooled at the other, and we have thermo¬ 
electric as well as hydro-electric batteries. There are also 
other sources of electricity, namely, machines like the 
Gramme machine, that are capable of giving the same effects 
as a battery. 
Here, however, we shall consider only those batteries that are 
used in practical telegraphy. 
Volta was the originator of the arrangement that was named 
after him, the voltaic pile or battery. This pile dates from 
1800, and was used for all the voltaic experiments made during 
the earlier part of the present century. 
De la Rive, observing the chemical effects produced on strips 
of two metals (zinc and platinum) immersed in acidulated water, 
has given us what may be called our present form of battery. 
Although the experiments of De la Rive, of Jacobi, and of 
Moride had electro-plating for their immediate object, they gave 
Daniell the idea of his battery, which is merely a simple form of 
an electro-plating apparatus. 
Danielfs first battery was very complicated (fig. 130). 
Possessed with the idea of giving the apparatus perfect con¬ 
stancy, the inventor filled it with siphons to remove the 
saturated saline solutions, and supply fresh water, so that a 
