1 8 THE SCIENTIFIC PAPERS OF 



minated in gold points, under the inverted glass cups (or volta- 

 meters) and the rising of the gases of decomposition betrayed to 

 the attentive observer the passage of the current. 



The difficulty of dealing with so many wires suggested to the 

 mind of Schweigger the same expedient which Lomond had 

 recourse to with regard to static electricity, that of reducing the 

 number of line wires to a single metallic circuit, and the receiving 

 instrument to a single decomposing cell, having recourse to 

 repetition, and to differences in the duration of succeeding currents, 

 in arranging his telegraphic code. 



It seems not improbable that if electrical science had made no 

 further advances, the projects of Soemmering and Schweigger 

 would have gradually expanded into practically working chemical 

 electric telegraphs, such as have been proposed at a much later 

 period by E. Davy, 1838, Morse, 1838, Bain, 1843, and Bakewell 

 in 1848, which last is particularly interesting inasmuch as not 

 mere signals or conventional marks are received by it, but a fac- 

 simile of the message, previously written with a solution of shellac 

 upon a metallic surface. 



The discovery of Oersted in 1821, which under the hands of 

 Schweigger, Ampere, Arago and Sturgeon, soon expanded into 

 electro-magnetism, turned the tide of invention into quite another 

 direction. Ampere was the first to propose an electro -magnetic 

 needle telegraph consisting of 24 needles, representing each a letter 

 of the alphabet, and 25 line wires, the extra line wire being 

 intended for the metallic return circuit common to all. Eitchie 

 executed, in 1832, a model of Ampere's telegraph, with an essential 

 improvement, to the effect that each needle, by its motion, moved 

 a screen disclosing a letter of the alphabet. 



Another version of the same general arrangement was patented 

 by Alexander of Edinburgh, as late as 1837, Fechner of Leipzig, 

 and Schilling von Canstadt of Russia, proposed, in 1832, apparently 

 independently of each other, a single-needle telegraph with 

 deflection of the needle to the right and left ; and Fechner was 

 the first to prove, by calculation, the power of the galvanic current 

 to traverse a great length of line wire. 



Gauss and Weber, of G-oettingen, took up the subject of electric 

 telegraphs at about the same time, but had not proceeded far when 

 their attention was diverted by the great crowning discovery of 



