VOLTAIC CURRENT. 



Fig. l. 



difference, however, that the electric fluid moves along the wire 

 more freely, in an almost infinite proportion, than does either 

 water or gas in the tubes which conduct them. 



If, then, a wire, coated with a non-conducting substance, 

 capable of resisting the vicissitudes of weather, were extended 

 between any two distant points, one end of it being attached 

 to one of the extremities of a galvanic battery, a stream of 

 electricity would pass along the wire -provided the other end of 

 the wire were connected by a conductor with the other extremity 

 of the battery. 



21. How the fluid transmitted to a distant station is made to 

 produce the effects by which messages are expressed will be 

 explained hereafter, meanwhile it will be necessary first to explain 

 the form and principle of the voltaic batteries used for tele- 

 graphic operations, and secondly the expedients by which the 

 current is transmitted and suspended, and turned in one or 

 another direction at the will of the operator at the station from 

 which despatches are transmitted. 



To comprehend the principle of the voltaic battery, let us 

 suppose that two strips cut, one z z from a sheet of zinc, and the 

 other cc (fig. 1) from a sheet of cop- 

 per, are immersed without touching 

 each other in a vessel containing 

 water slightly acidulated. To the 

 upper edges P and x of the strips let 

 two pieces of wire P p and N n, be 

 soldered. In this state of the appa- 

 ratus no development of the electric 

 fluid will be manifested ; but if the 

 ends p and n of the wires be 

 brought into contact, an electric 

 current will set in, running on the 

 wires from p, the point where the 

 wire is soldered to the copper c c, 

 to x, the point where the other wire 

 is soldered to the zinc z z. This 

 current will continue to flow so long 

 as the ends j9 and n of the wires are 

 kept in mutual contact, and no longer. The moment the ends p 

 and n are separated, the current ceases. 



22. The commencement of the current upon the contact of the 

 wires, and its cessation upon their separation, are absolutely 

 instantaneous ; so much so, that if the ends^ and n were brought 

 into contact and separated a hundred times in a second, the flow 

 and suspension of the current being simultaneous with the 



121 



