298 



OBSERVATIONS OF THE 



Magnetic Dip at Peru, Illinois. Latitude 41° 23' N.; Longitude 89° 5' W. 

 Place of observation near the landing. 



Date. 



Hour. 





Needle. 



No 



Readings. 



Dip. 



1841, Sept, 16, 



1—3, P. 



M. 



No. 1, 





40 



71° 55'.9 



(( 



(( 





No. 1, poles reversed. 





40 



47.1 



(( 



(( 





Mean of No. 1, 





80 



51 .5 



(( 



(t 





No- 2, 





40 



67.4 



(( 



(( 





No. 2, poles reversed, 





40 



39.3 



<( 



(( 





Mean of No. 2, 





80 



53.3 



<( 



(( 





Mean of both needles, 





160 



71 52.4 





Observations 



repeated 



on the hill hack of the Landing. 





Date. 



Hour. 





Needle. 



No 



Readings. 



Dip. 



1841, Sept. 16, 



3—5, P. 



M. 



No. 1, 





40 



71°41'.3 



(( 



(( 





No. 1, poles reversed, 





40 



52.7 



(( 



(( 





Mean of No. 1, 





80 



47.0 



(( 



(( 





No. 2, 





40 



38.6 



(t 



i( 





No. 2, poles reversed, 





40 



66.3 



(C 



(( 





Mean of No. 2, 





80 



52.5 



l( 



(( 





Mean of both needles. 





160 



71 49 .8 



Mean of 320 read 



ings with both needles, 



• • • • 



^ 



; 



71 51 .1 



Magnetic Dip at Pekin, Illinois. Latitude 40° 35' N.; Longitude 89° 36' TV. 



Place of observation a few rods below the steamboat landing. 



Date. 



Hoar. 



Needle. 



No 



Readings. 





Dip. 



, Sept. 18, 



9—11, 



A.M. 



No. 1, 





40 



71 



= 12'.9 



(( 



<< 





No. 1, poles reversed. 





40 





9.3 



(( 



<< 





Mean of No. 1, 





80 





11 .1 



(( 



(( 





No. 2, 





40 





29.9 



<( 



(( 





No. 2, poles reversed, 





40 





0.8 



K 



(( 





Mean of No. 2, 





80 





15.3 



t( 



<( 





Mean of both needles, 





160 



71 



13.3 



Magnetic Dip at mouth of Copperas Creek, Illinois. Latitude 40° 30' N.,- Longitude 89° 48' W. 



Date. 



Hour. 



Needle. 



No. Readings. 



Dip. 



1841, Sept, 18, 



2—3, P. M. 



No. 1, 



40 



70° 56'.4 



The observations were here interrupted, but from a comparison of preceding 

 and following observations at Pekin and Alton, the dip at Copperas Creek may 

 be inferred to be 71° 4'.0. 



