APPLICATION OF THE ELECTRIC TELEGRAPH. 359 



velocity of 18,000 miles per second, and from the ex- 

 periments of October 31st a velocity of 18,330 miles per 

 second.* 



On the 12th of November, 1849, Professor Mitchell 

 performed a series of experiments on the line between 

 Pittsburg and Cincinnati, the circuit being formed by a 

 wire from Cincinnati to Pittsburg, and a second wire from 

 Pittsburg to Cincinnati, constituting a length of 607 

 miles. The wave time deduced from these experiments 

 was Os.02128, corresponding to a velocity of 28,524 miles 

 per second, f 



The importance of an accurate determination of the 

 velocity with which signals travel along the wires of the 

 electric telegraph, induced the superintendent of the Coast 

 Survey to undertake a very extensive series of experi- 

 ments for this purpose. On the night of February 4th, 

 1850, the telegraph lines from "Washington to Pittsburg, 

 from Pittsburg to Louisville, and from Louisville to St. 

 Louis were all united, so that signals were transmitted 

 directly from "Washington to St. Louis, and recorded on 

 the registers of the four telegraph offices. The length 

 of the wire constituting the telegraph line was 1049 

 miles, and the shortest distance between the extreme 

 stations through the ground was 742 miles. The tem- 

 perature was at zero of Fahrenheit from Pittsburg to 

 St. Louis, and at eight degrees at "Washington. The 

 insulation was so perfect, that each station could receive 



* Proceedings Am. Assoc, at New Haven, p. 97. 

 f Astronomical Journal, vol. L, p. 16. 



