154 



Terrestrial Magnetism. 



JVo. 11. Louisville,'' Kentucky, Lat. 38° 3' JV., Lon. 85° 30' W. Sept. 7, 1840. 



* The above observations were made on Corn Island, in the Ohio. At Jacob's 

 Woods, two miles south of the island, the dip was 69° 57'. 1. 



On August 31, 1839, the dip on Corn Island was . . 70° 08' 



Sept. 7, 1840, " " " . . 70° 04' 



March 11, 1840, the dip at Jacob's Woods was . 69° 57' 



Sept. 7, 1840, " " " . 69° 57' 



The above exhibits the greatest change of dip which I have ever noticed in so 



short a distance as two miles. 



