70 



MAG N E T I C S U 11 V B V O P 1' E N N S V L VANIA. 



mination of curvature of fee isoclinal Hues; and, finally, the following expression 



was adopted : — 



7= 73°.25 + 0.912 JL — 0.069 dM cos L. 

 This equation represents fee observations as follows: — 



The isoclinal lines of 71°, 72°, 73°, 74.°, and 75°, pass through the following 



Comparison of the Observed and Computed Dip. 



(All stations where the dip has been found indirectly only, by means of the Lloyd needles, are marked with an 

 asterisk ; 27 in number. Total number of stations, 48.) 



Group I. 



Observed dip. 



Computed dip. 



Diff. observed. 

 — computed. 



New York 



I la -ton 

 ♦Princeton 

 ♦Doylestown 

 * Reading 



Philadelphia 



* Frenchtown 



Haiti! 



Washington 

 Harrisburg 

 Near Mercei 



72°. 66 

 72.65 

 72.64 



72.39 



72.51 

 71.95 



Gkoi p 1 1. 



rsbu 



rg 



71.67 

 71.57 

 71.26 

 72 34 

 71.79 



72°. 93 

 72.80 

 72.51 

 72.44 



72.42 

 72.14 



— 0°.27 

 —0. 1 5 

 + 0.13 

 —0.05 

 + 0.12 

 —0.19 



