THE INTENSITY OP TERRESTRIAL MAGNETISM. 263 



manner of producing telegraphic signs, by means of galvanic 

 currents. 



As soon as it was known that the action of a A-^oltaic pile pro- 

 pagated itself through a very long chain, the inference seemed 

 obvious that these natural forces might be employed for tele- 

 graphic purposes; and, thirty years ago*, when but a small 

 portion of the galvanic actions were known, Sommering pro- 

 posed the evolution of gas for the purpose. The magnetic ac- 

 tions of galvanic currents, which were subsequently discovered, 

 are far better adapted for complicated signals ; yet it is sur- 

 prising, that since Oersted's discovery, many years elapsed be- 

 fore any one seems to have thought of applying them to this 

 purpose. It is true that it was not possible to fonn a well- 

 grounded opinion of their applicability on a large scale, with- 

 out an accurate quantitative knowledge of the decrease in force 

 of galvanic cuirents, resulting from the length and quahty 

 of the conducting wires ; on which subject, before Ohm and 

 Fechner, very imperfect and erroneous notions were entertained. 

 With a view chiefly to the performance, on a large scale, of si- 

 milar experiments on the law of the force of galvanic currents 

 under different circumstances, a connecting wire was establish- 

 ed in 1833 between the Astronomical Observatory and the 

 Physical Cabinet ; the merit of the execution of this difficult 

 project is due to Prof. Weber. This chain was from the first 

 frequently employed for telegraphic signals ; not merely for 

 simple ones in the daily compaiison of the clocks, but compli- 

 cated signals were also tried for the sake of experiment, and the 

 possibihty of communicating letters, words, and whole phrases, 

 was even then an ascertained factf. In these experiments an 

 hydro-galvanic current was employed, excited only by very weak 

 means, viz. a single or a double pair of plates, and unacidulated 

 water ; I shall not, however, stop here to describe the method 

 then employed, as I have since substituted for it one entirely 

 different. In the first method there was this inconvenience; 



* I have learnt from a note communicated to me by von Humboldt, that 

 B^tancourt had, ten years ago, laid down a wire from Aranjuez to Madrid, by 

 means of which telegraphic signals could be effected by the discharge of a 

 Leyden flask. Although no detailed account of the result appears to be known, 

 there can be no doubt of the success of such an experiment, if properly per- 

 formed ; but such a method must always have been limited to conveying an af- 

 firmative or negative reply to a few previously-concerted questions. 



t The first public notice of these experiments is in the GiJtt. gelehrten Anzeige, 

 1834, p. 1273. See Schumacher's Jahrbuch for 1836, p. 38. 



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