THE ELECTRIC TELEGRAPH. 



is then poured into the vessel v v, and concentrated nitric acid 

 into v v. The electric fluid issues from a wire connected with the 

 charcoal, and returns by one connected with the zinc. 



Messrs. Deleuil and Son, of Paris, have fabricated batteries on 

 this principle with great success. I have one at present in use 

 consisting of fifty pairs of zinc and carbon cylinders, the zinc being 

 2 1 inches diameter, and 8 inches high, which performs very 

 satisfactorily. 



The chief advantage of Daniel's system is that from which it 

 takes its name, its constancy. Its power, however, in its most 

 efficient state, is greatly inferior to that of the carbon or platinum 

 systems of Bunsen and Grove. A serious practical inconvenience, 

 however, attends all batteries in which concentrated nitric acid is 

 used, owing to the diffusion of nitrous vapour, and the injury to 

 which the parties working them are exposed by respiring it. In 

 my own experiments with Bunsen' s batteries the assistants have 

 been often severely affected. 



In the use of the platinum battery of Grove, the nuisance pro- 

 duced by the evolution of nitrous vapour is sometimes mitigated 

 by enclosing the cells in a box, from the lid of which a tube 

 proceeds which conducts these vapours out of the room. 



In combinations of this kind, Dr. O'Shaugnessy substituted 

 gold for platinum, and a mixture of two parts by weight of 

 sulphuric acid to one of saltpetre for nitric acid. 



The method of producing the electric fluid by the mutual action 

 of magnets and bodies susceptible of magnetism will be described 

 hereafter. 



35. Although each of the simple combinations described above 

 would produce an electric current, which, being transmitted upon a 

 conducting wire, would be attended with effects sufficiently distinct 

 to manifest its presence, such a current would be too feeble in its 

 intensity to serve the purposes of a telegraphic line ; and as no 

 other simple voltaic combination yet discovered would give to a 

 current the necessary intensity, the object has been attained by 

 placing in connection a series of such combinations, in such a 

 manner that the currents produced by each of them being trans- 

 mitted in the same direction, on the same conducting wire, a 

 current having an intensity due to such combination may be 

 obtained. 



Such a series of simple voltaic combinations, so united, is called 



a VOLTAIC BATTEBT. 



128 



