CHAP, ur.] ELECTRIC TELEGRAPHY. 545 



signals agreed upon and produced at the other station, that is, at the 

 opposite extremity of the conducting wires, by the successive inter- 

 ruption of the current. 



A new advance in the science, namely, the discovery of the action 

 of currents on magnetized needles (OErsted, 1820), was the starting- 

 point of new researches which led at last to the desired end. Even 

 in the same year as this fundamental discovery Ampere defined this 

 end and indicated in these terms the means of attaining it. 



" We could," says this illustrious physicist and philosopher, " by 

 means of as many conducting wires, and of magnetized needles, as 

 there are letters, establish, by the aid of a battery placed at a distance 

 from the needles, and which could be made to communicate alternately 

 by its two extremities with those of each conductor, a sort of telegraph 

 which might write all the details we wished to transmit, over the 

 intervening space, to the person charged to observe the letters placed 

 over the needles. By fixing above the battery a key-board whose 

 keys denoted the same letters, and by establishing the communication 

 by their depression, this means of correspondence could be easily carried 

 out, and would require no more time than that necessary for touching 

 the key at one place, and reading each letter at the other." 



Ampere's idea was not realized in the shape in which he formulated 

 it. The number of galvanometers, each of which was to correspond 

 to a single letter of the alphabet and to each further sign to be 

 transmitted would have been too great, but we shall see in time, when 

 we describe the needle electro-magnetic telegraph, that it is the same 

 principle that dictates its construction. It is to Wheatstone that we 

 owe the improvements and simplifications which have given to 

 Ampere's conception all its practical importance. 



But before it arrived at a complete realization, this conception was 

 applied in various ways, by Schilling in 1833, by Gauss and Weber in 

 1835, by Piichtie and Alexander in 1837. The first of these applied 

 his system at St. Petersburg, but on a small scale. " Five platinum 

 wires were inclosed in a cable of silk each joined by one of its 

 ends to a multiplier, and by the other to a key-board like that of a 

 piano. On sending the current of a battery through one of these wires, 

 by putting down the key corresponding to it, the needle deviated to 

 one side or the other according to the direction of the current. This 

 formed with the five needles ten different signs. Messrs. Piichtie and 



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