78 



Determinalion of the difference of Longitvde between Chicago and 

 the City of Rock Island, by electric signals for comparisons of 

 time, March 1st, 1859. 



Sidereal Chronometer No. 2557, fast, of Rock Island, sidereal 

 time (at Sh. 55m. 42s. sidereal time), Ih. 38m. 42s.43. 



Rate per sidereal day, + 3.S.93; or per sidereal hour, + 0s.l637. 



Mean solar Chronometer No. 141, slow, of Chicago, mean solar 

 time (at 10/t. 29:^. 44s. mean time), 4m. 43s.50. 



Rale per mean solar day, — Os.008; or per mean solar hour, — 

 Os.0003. 



1st. — Chicago signals recorded at both stations. 



1st Mean. — Electric signals sent from Chicago to the City of 

 Rock Island, __-__- 



11 45.687 



2d Mean. — Electric signals sent from the City of llock Island 



to Chicago, - - - - - - 11 45.690 



1st Mean. — Electric signals sent from Chicago to the City of 



Rock Island, as above, - - - - - 11 45.687 



Result: — llock Island Station is west, in longitude, of Chicago 

 observing Station No. 3, l>y a mean of the two sets of 

 signals, - + 11 45.69 



