80 



Determination of the difference of Longitude between Chicago and 

 the City of Rock Island, Illinois^ by electric signals for com- 

 parisons of time, Jidy 29th, 1859. 



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

 (at 19h. 53m. 36s. sidereal time), 1/t. 57m. 25s.94. 



Rate per sidereal day, + 7s.61 ; or per sidereal hour, -f 0s.317. 



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

 time (at llA. 36/;i. mean time), 1/t. 57m. 25s.94. 



Rate per mean solar day, — Os.755; or per mean solar hour, — 

 05.03146. 



1st. — Chicago signals recorded at both stations. 



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

 Rock Island, ______ 



n 46.227 



2d. — The City of Rock Island signals recorded at both stations. 



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



to Chicago, - - - - - - 11 46.23 



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



Rock Island, as above - - - - - 11 46.227 



Result: — Tiie centre of Wasliiiigton •Sqnare in the City of Rock 

 Island is west, in longitude, of Chicago observing Station 

 No. 3, by a mean of the two sets of signals, - -j- 11 46.228 



