APPLICATION OF THE ELECTRIC TELEGRAPH. 361 



On the 8th of July, 1850, Mr. Walker tried a variety 

 of experiments, for the purpose of testing, by means of 

 the chemical telegraph, the velocity of propagation of 

 the electric current indicated by the Morse telegraph lines. 

 These experiments were performed on the line from 

 Boston to New York, on a circuit of 407 miles in length, 

 220 of which were of iron wire in the air, and 187 

 were through the ground. The marks were recorded on 

 paper, previously moistened with a solution of ferro- 

 cyanate of potassa. As there was no astronomical clock 

 in connection with the line, Mr. Walker tapped at in- 

 tervals of two seconds on the make-circuit key, and thus 

 graduated the chemical disc of paper at Boston and New 

 York. The operator at the New York office imprinted 

 in every third interval, between the marks of the grad- 

 uated scale, three short marks, which were also recorded 

 at both stations. These experiments, 63 in number, 

 indicated a difference of the New York marks on the 

 Boston time-scale, of about one second for every 12,000 

 miles.* 



The experiments made in July and August, 1852, be- 

 tween Washington and Petersburg, Ya., indicated a 

 velocity of the electric current equal to 9,800 miles per 

 second.f 



Numerous experiments have been made in France by 

 MM. Fiseau and Gounelle in 1850, and by MM. Bur- 



* Astronomical Journal, vol. I., p. 108. 

 f Coast Survey Report for 1852, p. 26. 



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