4 



On M. Hansteen's recent Magnetic 



observed ; and those in dotted lines exhibit the supposed com- 

 pletion of the curves, in parts of the hemisphere where the 

 intensity has not been as yet examined. The portions which 

 arrange themselves around the point in Hudson's bay are 

 chiefly laid down from observations made by myself in two 

 voyages of North-west discovery, those of 1818, and of 1819- 

 1820 ; — in a voyage in 1822 to the equatorial shores of the 

 Atlantic, and to several of the islands in the Atlantic and Carib- 

 bean seas, — and in a fourth voyage, in 1823, to Greenland, 

 Spitzbergen, and Norway. Their prolongations around the 

 point in Siberia are from the recent observations of M. Han- 

 steen and the gentlemen who accompany him. A brief notice 

 of each of the curves in succession will enable me to point out 

 generally the places which have furnished their respective 

 authorities. 



