58 



M A G X E T I (' S D R V E V OF 1' B N N S Y L V A MA. 



.Inly 21, 

 on. 28, 

 April 26, 

 July 20, 



Oct. 



Nov. 

 July 

 Sept. 

 Sept 



Recapitulation of the observed Dip at Philadelphia. 



Means. 

 1840 . . 71°52'.6- 



9, 



1, 



20, 



0, 

 12, 



1840 

 1841 

 1S41 

 1841 

 1841 

 1843 

 1st 3 

 1843 



71 



71 

 71 

 71 

 71 

 71 

 71 

 71 



53.1 

 60.6 

 57.0 

 58.2 

 59.1 

 56.5 

 59., 

 57.6 ) 



"I 



71° 55'. 4 



71 58.1 



71 57.9 



Dec. 1840 



Oct. 1st I 



Aug. L843 



By means of the preceding results for horizontal intensity X, and dip 8, we find 



the total intensity $, as follows : — 



<p = X sec 8. 



1 From the 2d Vol. of the Girard College Uagnetical and Meteorological observations, we tiii'l the dip at Phila- 

 delphia .is follows : — 



1.1. 1, 71 5 '.'I. and LI. 3, 71 i:. - • 



hence resulting dip, 71° 50'. 5. 



1 Dip from 2'1 Vol. of Girard College observations. 



