350 



Ath. 1858, Septemher I8th. 



Time stars, u Andromedrc, east, and « Coronaj Bo- 

 realis, west. Also, eqiial altitudes oi" cc Pegasi. 



Latitude of Station: 

 By 15 circum-meridian altitudes of cc Aquila?, south, 

 combined with 26 circum-meridian altitudes of 

 y Cephei, north, 41° 53' 46" 



5th, — Same Night. 



By 28 circum-meridiam altitudes ofce Aquarii, and 22 

 circum-meridian altitudes ofli Aquarii, both south, 

 and a mean from which was taken as one quantity, 

 combined with 18 altitudes of Polaris (ctUrsse 

 Minoris), 41° 53' 45".8 



Mean ;— or latitude of station No. 3, by giving the oh- 



servations on each pair of stars an equal weight, 41° 53' 46". 3 



Reduction to the centre of the dome of the City 



Hall, or Court House of Chicago, - - - — 40". 1 



Latitude of the dome of the City Hall, or Court House 



of Chicago, from this series, - - - 41° 53' 06". 2 



Extreme difference in the 5 results - - - 1".7 



The result of this series gives the latitude 3". 5 less than was report- 

 ed in my letter of the 2d of April last. As they were hastily made 

 to answer a call upon me by some of the citizens of Chicago to know 

 the approximate latitude of the place, I do not propose to give them a 

 weio-ht here, but I would offer the result from the five sets of observa- 

 tions made in August and September as a close approximation. 



I would adhere to the longitude of this position as given in my let- 

 ter of April 2d, namely: 5^. 50m. .32s.08=87° 38' 0r'.2 west of the 

 meridian of Greenwich. 



From these determinations, and our connections by triangulation, 

 we obtain the positions of other stations in the city of Chicago, and as 

 I am obliged, from peculiar circumstances, to use sometimes one and 

 sometimes another, for the purpose of making chronometric compari- 

 sons, in order to determine the longiludes of other important places in 

 the west, I beg leave to present them here in a tabulated form for 

 future convenient reference. They are: — 



