296 OBSERVATIONS OF THE 



Date. Hour. Needle. No. Readings. Dip. 



1841, Sept. 8, 1—3, P. M. No. 2, poles reversed, 40 73° BO'.O 



" " Mean of No. 2, 80 68 .6 



" " Mean of both needles, 160 74 8.3 



Mean of 320 readings of both needles, 74 6 .5 



Magnetic Dip at Campbell's, Wisconsin. Latitude 43° 1' N.; Longitude 89° 26' W. 



Fifteen miles from Madison; ten miles from Blue Mounds. 



Date. 



Hour. 





Needle. 



No. 



Readings. 





Dip. 



, Sept. 9, 



5—7, A. 



M. 



No. 1, 





40 



73 



'31'.8 









No. 1, poles reversed, 





40 





25.0 









Mean of No. 1, 





80 





28.4 









No. 2, 





40 





42.3 









No. 2, poles reversed, 





40 





13.3 









Mean of No. 2, 





80 





27.8 









Mean of both needles, 





160 



73 



28.1 



Between this place and Madison, distant only fifteen miles, and near the 

 same parallel, the difference of dip is 38'. 4, whereas they might have been an- 

 ticipated to have nearly the same dip. There seems to be powerful local at- 

 traction near Madison. Iron ore has been found on the lake shore, close to the 

 village, and the surveyor who laid out the town complained that the direction 

 of his compass needle was exceedingly irregular. 



Magnetic Dip at BickoFs, Wisconsin. Latitude 42° 58' N.; Longitude 89° 47' W. 



Ten miles from Blue Mounds; nine miles from Dodgeville. 



Date. 





Hour. 





Needle. 



No. 



Readings. 





Dip. 



1841, Sept. 9, 



11- 



-1, P. 



M. 



No. 1, 





40 



73 



= 35'.0 



(( 









No. 1, poles reversed. 





40 





45.7 



(( 









Mean of No. 1, 





80 





40.4 



(i 









No. 2, 





40 





26.2 



(C 









No. ,2, poles reversed, 





40 





51.2 



(( 









Mean of No. 2, 





80 





38.7 



(( 









Mean of both needles. 





100 



73 



39.5 



Magnetic Dip at Mineral Point, Wisconsin. Latitude 42° 51' N.; Longitude 89° 58' W. 

 Place of observation a few rods back of Franklin House. 



Date. Hour. Needle. No. Readings. Dip. 



1841, Sept. 10, 10—12, A. M. No. 1, 40 73° 27'.8 



" " No. 1, poles reversed, 40 21 .9 



