300 



OBSERVATIONS OF THE 



Date. 



Hour. 





Needle. 



No 



Readings. 



Dip. 



1841, Sept, 25, 



2-4, P, 



M. 



Mean of No. 1, 





80 



69° 45'.3 



(( 



(( 





No. 2, 





40 



59.1 



(C 



(C 





No. 2, poles reversed. 





40 



35.9 



(< 



C( 





Mean of No. 2, 





80 



47.5 



(C 



(( 





Mean of both needles. 





160 



69 46.4 



Mean of 320 readii 



igs of both needles, , 



.... 



. 



, , 



69 45.7 



Magnetic Dip at Edwardsville, Illinois. Latitude 38° 50' N,; Longitude 89° 53' W, 

 Place of observation a few rods west from tlie court house. 



Date. 



Hour. 





Needle. 



No 



Readings. 



Dip. 



, Sept. 23, 



10—12, 



M. 



No. 1, 





40 



69° 57'.6 





(( 





No. 1, poles reversed, 





40 



46.4 





(( 





Mean of No. 1, 





80 



52.0 





(( 





No. 2, 





40 



63.9 





(( 





No. 2, poles reversed. 





40 



62.9 





« 





Mean of No. 2, 





80 



63.4 





(( 





Mean of both needles, 





160 



69 57 .7 



No. Readings. 





Dip. 



40 



69 



° 37.9 



40 





49.0 



80 





43.4 



40 





53.5 



40 





56.1 



80 





54.8 



160 



69 



49.1 



Magnetic Dip at Bunker Hill, Illinois. Latitude 39° 4' N.; Longitude 89° 53' W. 

 Place of observation one mile north of the village. 



Date. Hour. Needle. 



1841, Sept. 24, 12—2, P. M. No. 1, 



No, 1, poles reversed, 

 Mean of No. 1, 

 No. 2, 



No. 2, poles reversed, 

 Mean of No. 2, 

 Mean of both needles, 



Magnetic Dip at Monticello, Illinois. Latitude 38° 57' N.; Longitude 90° 5' PF. 



Place of observation near the Female Seminary. 



Date. Hour. Needle. 



1841, Sept. 25, 9—11, A. M. No. 1, 



" " No. 1, poles reversed, 



" " Mean of No. 1, 



" " No. 2, 



" " No. 2, poles reversed, 



" " V Mean of No. 2, 



" '* Mean of both needles. 



No. Readings. 





Dip. 



40 



69 



° 50'.2 



40 





34.8 



80 





42.5 



40 





20.4 



40 





50.1 



80 





35.2 



160 



69 



38.9 



