i Velocity of the Galvanic Current in Telegraph Wires. 161 
of the case permits. The difference of temperature, at stations so 
distant from one another, makes it appear unadvisable to introduce 
any correction for temperature, even were such a refinement of 
: the same order of magnitude with the unavoidable errors of our 
ioe ‘measurements, and therefore congruous with their character. The 
temperature was, in all cases, as low as the freezing point—the 
insulation not being sufficiently perfect at other times to allow 
4 communication between very distant stations. The distances 
used are the following, in miles~ten per cent. having been added. 
re, 
Washington, Washington, 
172 Philadelphia, | 74 Harper's Ferry, 
881 209 New York, 165 91 Cumberlar 
850 469 260 Cambridge. 309 235 144 Wheeling, © 
4 413 269 Cincinnati. 
578 
Washington to Cambridge, through the ground, . . 380 
ashington to Cincinnati, ve is a vi ag aa 
The great length of wire assigned to the part between New 
York and Philadelphia is a consequence of the distance to which 
the line ascends the Hudson before finding a crossing-place. 
Date. | Terminus. Velocity. Prob. error. 
Sos sree os * if ae = 
1849 Jan. 23, | Cambridge, | 18000 | 150 
t. 31, Cincinnati, 18550 | 124 
1850 Feb. 4, St. Louis, 14900 10 
Seokeb. 6 Charleston, 16856 
The resultant is 15890 miles per second, as the most probable 
value, 
Mr. Walker’s experiment, 1850, July 8, with the Electro- 
chemical Telegraph,* gave for the velocity between Boston an 
New York (220 miles) 13333 milesa second. The wire of Bain’s 
Telegraph is however of a different size from the other lines, and 
18 Coated over to prevent oxydation. Should we assume the sig 
nals to have been transmitted through the ground, Feb. 5, and 
uly 8, we should obtain the respective velocities 10690 and 
10820 miles per second. 
In spite of the mutual confirmation of the several results by 
he another, and although the accordance is even remarkable, 
Considering the numerous obstacles and sources of error, it is 
hevertheless true that the observations might be still better repre- 
_ Sented by supposing the velocity to be different at different parts 
of the line. Is this assumption admissible? It is, if we have 
Teason to suppose that the velocity is dependent on the in- 
tensity of the current—for several batteries were interposed at 
sis late stations on the line. The most powerful battery was 
Usburg, consisting of fifty Grove’s cups, each holding a pint, 
comparison of the different velocities appears to indicate that 
: * Ast. Journ, i, p. 105. 
Serums, Vol. XI, No. 32—March, 1851. 
