108 



ADDITIONAL OBSERVATIONS OF THE 



Magnetic Dip at Princeton, New Jersey. Latitude 40° 22' N.; Longitude, 4h. 58m. TV. 

 Place of observation an open field, one hundred rods south of the colleges. 



Date. 





Hour. 



Needle. 



No 



Readings. 





Dip. 



1839, Sept. 21st, 



10- 



-12, A.M. 



No. 1, 





40 



72= 



47'.4 





( 





No, 1, poles reversed. 





40 





47.4 









Mean of No. 1, 





80 





47.4 





i 





No. 2, 





40 





52.9 









No. 2, poles reversed, 





40 





40.8 









Mean of No. 2, 





80 





46.8 









Mean of both needles, 





160 



72 



47.1 



Magnetic Dip at Philadelphia, Pennsylvania. Latitude 39° 57' iV.; Longitude 5/t. Im. W. 

 Place of observation the yard in front of President Bache's house. 



Dale. 



Hour. 



Needle. 



No. 



Readings. 



Dip. 



J 839, Sept. 23d, 



lOi— 12, M. 



No. 1, 





40 



72° 8'.6 







No. 1, poles reversed, 





40 



11 .3 







Mean of No. 1, 





80 



10.0 







No. 2, 





40 



71 58.9 







No. 2, poles reversed. 





40 



72 9.6 







Mean of No. 2, 





80 



4.2 







Mean of both needles, 





160 



72 7.1 



Magnetic Dip at Baltimore, Maryland. Latitude 39° 17' N.; Longitude 5h. 7m. W. 

 Place of observation the grove north of Washington Monument. 



Needle. No. Readings. Dip.' 



No. 1, 40 71° 54'.3 



No. 1, poles reversed, 40 46 .3 



Mean of No. 1, 80 71 50.3 



Date. 



Hour. 



839, Sept. 25th, 



7—8, A. M 



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