72 



OBSERVATIONS TO DETERMINE THE MAGNETIC DIP, ETC. 



Magnetic Dip at Streetsboro, Ohio. Latitude 41° 15' N.; Longitude 81° 20' W. 

 Place of observation a quarter of a mile west of the village. 



Date. 



Hour. 



Needle. 



No 



Readings. 





Dip. 



1840, Oct. 16th, 



9— 11, A.M. 



No. 1, 





40 



72' 



' 46'.2 







No. 1, poles reversed, 





40 





55.8 







Mean of No. 1, 





80 





51.0 







No. 2, 





40 





52.6 







No. 2, poles reversed. 





40 





57.4 







Mean of No. 2, 





80 





55.0 







Mean of both needles, 





160 



72 



53.0 



Magnetic Dip at TaUmadge, Ohio. Latitude 41° 6' N.; Longitude 81° 26' W. 

 Place of observation the same as formerly. 



Date. 



Hour. 



Needle. 



No 



Readings. 





Dip. 



1840, Oct. 31st, 



2— 3i, P. M. 



No. 1, 





40 



72 



' 53. 5 







No. 1, poles reversed. 





40 





44.1 







Mean of No. 1, 





80 





48.8 







No. 2, 





40 





47.6 







No. 2, poles reversed, 





40 





47.5 







Mean of No. 2, 





80 





47.5 







Mean of both needles. 





160 



72 



48.2 



This result is almost identical vv^ith the former observation, indicating that 

 the effect of the iron key was scarcely appreciable. 



The preceding observations, as w^ell as those which I have formerly made in 

 Ohio and Michigan, are tolerably well represented by parallel, straight, and 

 equidistant isoclinal lines, running from N. 80° W. to S. 80° E.; and the line 

 of 73° passes five or six miles south of Cleveland. 



