186 ELEMENTS OF STATIC ELECTRICITY. 



ances, are the result of corresponding disturbances in 

 these electric movements. 



OBSERVATIONS ON TELEGRAPH LINES. The tel- 

 egraph affords special facilities for observing many of 

 the phenomena pertaining to terrestrial and atmospheric 

 electricity, by means of its long lines of nearly uniform 

 conductivity, insulated in the air, having earth con- 

 nections at points remote from each other, and extend- 

 ing, in the United States, chiefly, either at right angles 

 to the magnetic meridian, or parallel with it. 



These facts have been recognized; and, within the 

 last five years, observations have been made, on a 

 limited scale, in the United States, and in Europe. 

 These observations have been somewhat desultory and 

 local ; no general, extended, well established system 

 having yet been instituted. 



During the fall and winter of 1883-84, a series of 

 observations was made on a line belonging to the 

 Postal Telegraph Co.; extending, at first, from New 

 York City to Meadville, Pa.; 509 miles by wire, 325 

 direct; but subsequently completed to Chicago; 1058 

 miles by wire, 725 direct. The observations from Oct. 

 18 to Nov. 20, 1883, were between New York and Mead- 

 ville; and the subsequent observations, which were con- 

 tinued during November and December, 1883, and part 

 of February, 1884, were between New York and Chicago. 



The line consisted of a large copper wire having a 

 steel core ; thus combining conductivity and strength ; 

 and the object of the observations was to ascertain the 

 relations of the electric current to difference of temper- 

 ature. They were made daily, at both ends of the line, 

 at the hours when it was least occupied with other 

 business, 8 to 8.30 A.M., 5 to 5.30 and 11 to 11 30 P.M. 



