716 Experiments on the communication of £Sept. 



M. Bazin indeed admitted this freely, when he found that not one 

 of the electrical machines I placed at his disposal could by ordinary 

 manipulation be made to evolve the least sign of excitement. But 

 even effecting the excitement, which I have done by enclosing the 

 machines within a glass case hermetically sealed, and supplied with 

 air artificially dried, still it is impossible so to insulate the external 

 conductors, as to prevent the dispersion of the excitement outside the 

 apparatus. 



§ 2. — Telegraphs by Chemical decomposition. 

 In Steinheils' historical sketch we find that Soemmering, in 1807, em- 

 ployed a voltaic battery provided with thirty-five conductors, each termi- 

 nating in a gold pin set in a tube ; on completing the connexions the 

 water is decomposed and the ascent of bubbles of gas indicates the 

 signal. This system is, however, only available for very short dis- 

 tances, as the decomposing power of the termination of any pair of 

 conductors, the diameter being the same, diminishes rapidly by 

 lengthening the wire. The law of the diminution, Ritchie has attempted 

 to establish, but his experiments are not considered to be conclusive ; 

 its rapidity may be shewn by an experiment I performed in 1839. 

 A voltaic battery, the conductors of which were six feet long, decom- 

 posed water to the rate of forty cubic inches of oxygen and hydrogen gases 

 in three minutes. Conductors of the same diameter, but thirty -six feet 

 long were next employed; the battery then only evolved twenty-five 

 cubic inches of the gases ; with wires of 200 feet only eleven inches 

 were obtained ; still the battery was constant in its action, for with the 

 original conductors at the close of the experiments it still gave forty 

 cubic inches. Again in the experiments at the Botanical Garden in 

 1839, no chemical decomposition — even of the most yielding of all 

 compounds, the ioduret of potassium — could be performed at the 

 termination of one and a half miles, whereas other manifestations of 

 electrical action were readily procurable at the termination of twenty- 

 one miles of wires. 



§ 3. — Telegraphs by volta-magnetic deflection. 

 The next method employed is the deflection of the magnetic needle 

 by voltaic or magnetic electricity. I may remind the general reader that 

 whenever electrical vibrations occur in exceedingly rapid intervals in an 

 insulated wire surrounding and in the same direction with a ba- 

 lanced magnetic needle, the needle is deflected, either east or west 

 according to the order in which the ends of the surrounding coil are 



