20 THE ELECTRIC TELEGRAPH. 



tion of this telegraph, will illustrate the foregoing. A A is a 

 sectional view of the glass reservoir. A B c .... 8 9 are 

 the thirty-five gold points of the voltameter arrangement, 

 passing through the bottom of the glass reservoir. The 

 lower ends of the thirty-five gold points were soldered to insu- 

 lated copper wires passing through the tube E to the trans- 

 mitting station. Here the wires, marked with the respective 

 letters and numerals, were insulated on a wooden support, K K. 

 The ends of the terminals were furnished with holes, i, to 

 receive the poles B and c of the voltaic pile p N. 



The construction of this telegraph the first in which 

 voltaic electricity was employed involved an outlay which, 

 in conjunction with the slowness of working, would have 

 prevented its commercial utility even if the science had not 

 advanced by any of those astonishing strides which marked 

 its progress a few years afterwards. 



25. An improvement on the system of Sommering was 

 published by Schweiger, of Halle, in an appendix to his 

 memoir of Sommering. He suggested that, for the alarm, it 

 would be possible to employ a pistol by the connection of a 

 battery to the pile. In addition to this, he proposed to 

 diminish the number of wires used in Sommering' s telegraph 

 to two, by using two galvanic piles of unequal power, so 

 that the amount of gas given off in a certain time by the one 

 battery would be much more than by the other, and by 

 varying the time of development of the gas and of the inter- 

 vals, he proposed to form a code of signals. 



26. About the same time that Sommering invented his 

 telegraph, the same system was suggested by Professor Coxe, 

 of Pennsylvania, and described by him in a paper published 

 in Thomson's "Annals of Electricity," 1810. Coxe had 

 the idea also of telegraphing by means of the decomposition 

 of metallic salts. His systems were, as he described them, 

 considered, however, impracticable. 



