81 



Longitude of Chicago Station No. 3, 



h. m. s. 



Brought forward + 11 46.23 

 + 5 50 31.20 



2d Determination. July 29th, 18.59. 

 Longitude of centre of Washington Square, in the 



City of Rock Island, . - - - 6 02 17.43 



1st Determination, March 1st, 1859, - - 6 02 16.89 



Result, giving each Determination an equal weight: 



Longitude of the centre of Washington Square, in the 

 City of Rock Island, lUinois, vvestof the meridian 

 of Greenwich, - - - - 6 02 17.16 



Equal, in arc, to ... 90° 34' 17".4 W. 



Latitude of the same station, as before given, 41° 30' 37". 8 N. 



liy survey, departing from this station, based on an observed 

 azimuth of the sun on the 2d of March, 1859, for comparing our 

 courses with the true meridian, we obtained the positions of other 

 points, in the City of Rock Island, which may be useful for future 

 reference. We give them all in the following table, viz. — 



On the War Department map of 1857, the City of Rock Island is 

 laid down in latitude 41° 28' 39" N.,and longitude 90° 39' 13' W.; 

 which is 2 minutes of latitude less, and 4' 31" more, in longitude, 

 than our observations give. 



Note. — By applying a transcript from the Land Office Surveys, 

 contained in C. H. Stoddard's map of Scott county, Iowa, and Rock 



VOL. VII. L 



