MAGNETIC DIP IN THE UNITED STATES. 



297 



Date. 



Hour. 





Needle. 



No 



Readings. 



Dip. 



1841, Sept. 10, 



10—12, A. 



M. 



Mean of No. 1, 





80 



73° 24'.9 



(< 



a 





No. 2, 





40 



33.9 



(< 



(( 





No. 2, poles reversed, 





40 



7,1 



(( 



(( 





Mean of No. 2, 





80 



20.5 



(( 



(( 





Mean of both needles, 





160 



73 22.7 



Mean of 320 readings 



of both needles. 



Sept, 9, and 10, - 



. 



. 



73 23.0 



Magnetic Dip at Platteville, Wisconsin. Latitude 42° 43' N.; Longitude 90° 14' W. 

 Place of observation a few rods south of the village. 



Date. 



Hour. 





Needle. 



No. 



Readings. 



] 



Dip. 



1841, Sept. 11, 



7—9, A. 



M. 



No. 1, 





40 



73° 



16'.1 



<< 



(( 





No. 1, poles reversed, 





40 





21.9 



(( 



(( 





Mean of No. 1, 





80 





19.0 



« 



(( 





No. 2, 





40 





0.5 



{( 



(( 





No. 2, poles reversed, 





40 





29.9 



<( 



(( 





Mean of No. 2, 





80 





15.2 



(1 



(( 





Mean of both needles, 





160 



73 



17.1 



Observations repeated six 



rods south of the last Station. 







Date. 



Hour. 





Needle. 



No 



Readings. 





Dip. 



1841, Sept. 11, 



9— 11, A 



M. 



No. 1, 





40 



73< 



= 22'.0 



(( 







No. 1, poles reversed. 





40 





15.1 



(t 







Mean of No. 1, 





80 





18.5 



(( 







No. 2, ■ 





40 





28.8 



< 







No, 2, poles reversed, 





40 





4,5 



(( 







Mean of No. 2, 





80 





16.7 



(( 



". 





Mean of both needles, 





160 



73 



17.6 



Mean of 320 readinj 



ys with both needles, 



• • • 



. 



, 



73 



17.4 



Magnetic Dip at Galena, Illinois. Latitude 42° 28' N.; Longitude 90° 13' W. 



Place of observation nearly the same as formerly. 



Date. 





Hour 





Needle. 



No. Readings. 





Dip. 



1841, Sept. 



13, 



2—5, P. 



M, 



No. 1, 



40 



72^ 



61'.9 











No. 1, poles reversed, 



40 





70,5 











Mean of No. 1, 



80 





66.2 











No. 2, 



40 





49.4 











No. 2, poles reversed, 



40 





77.2 











Mean of No. 2, 



80 





63.3 











Mean of both needles. 



160 



73 



4.8 



Mean of 480 readi 



ngs of both needles, 



. . * . . 



. . , 



73 



3.0 



