HENRY AND THE TELEGRAPH. " 269 



no means the trivial and inefficient one so often represented by modern 

 writers. On the contrary, but for the practical difficulty of perfect and 

 constant insulation, owing to the intense self repulsion of mechanical 

 electricity and the reaction and retardation from induction currents in 

 ]ong lines of coated wire, this method would really constitute an eco- 

 nomical and satisfactory medium of distant communication. 



Steinheil in reference to this subject remarks : "All these experiments 

 put it beyond a doubt that frictional electricity may be employed for 

 giving signals at any distances, and that when these signals are properly 

 contrived they ofler convenient means of telegraphic intercourse. Fric- 

 tional electricity has besides as Gauss has already observed, the great 

 advantage of not losing any of its force by increasing the length of the 

 conducting wire, inasmuch as the whole of the electricity of one coating 

 of the jar must traverse the entire length of the wire (be it what it may) 

 to neutralize that of the other coating." * 



II. — TELEGRAPHS BY GALVANISM. 



The introduction of the galvanic battery by Yolta at the commence- 

 ment of the i^resent century f led many to experiment with its peculiar 

 current as a means of telegraphing. The only practicable forms of 

 simple galvanic telegraphs, are those whose indications are given by 

 chemical decompositions, and which thus form the class commonly known 

 as the " electro-chemical " ; and as these chemical indications usually leave 

 permanent markings, the class is also one of recording telegrai)hs. 



1808. Br. Samuel Thomas von Soemmering, of Munich, appears to 

 have been the first to apply Volta's invention to this purpose. "As long 

 ago as in 1807, Soemmering erected in the apartments of the Academy 

 of Sciences at Munich a galvanic telegraph, of which he has pub- 

 lished a detailed description in the Philoso])liical Transactions of Ba- 

 varia. [Miinchner Denkachriften dcr Koniglichen Akademie dcr Wis- 

 senscJiaften filr 1809, 1810. Math. phys. Classe, p. 401.] He em- 

 ployed the energy of a i^owerful voltaic pile to bring about the 

 decomposition of water by means of thirty-five gold i^ins immersed in 

 an oblong glass trough." | Each of these gilt electrodes was in con- 

 nection with one of the thirty-five wires forming the line, and was cov- 

 ered with an inverted test-tube filled with water, resting on a snbmerged 

 shelf in the oblong trough, as a gas-receiver. These small receivers 

 with their inclosed gilt pins or electrodes arranged in a row, repre- 

 sented 25 letters and 10 numerals. Such being the disposition at the 

 receiving end, the thirty-five line wires at the transmitting end were 

 each secured to a separate perforated brass plate. On connecting the 



* Sturgeon's Annals of Eleciricitij, etc. March 1839, vol. iii, p. 446. 



t Volta's description of his battery is given in a "Letter to Sir Joseph Banha," 

 president of the Royal Society of Loudon. {Phil. Trans. B. S. read June 2(5, 18U0, vol. 

 xc, pp. 403-4:U.) 



t Sturgeon's Annals of Elccincity, etc. Mar. 1839, voh iii, p. 447. 



