TERRESTRIAL MAGNETISM. 65 



surface, and by the judicious combination of the observations 

 made at them, important and unexpected results have been 

 arrived at. The subjection of the manifestations of the 

 magnetic force, as displayed on the earth's surface, to 

 determinate laws, which subjection, in relation to all 

 forces, is the proximate, but not the ultimate object of all 

 scientific inquiry, has been already satisfactorily esta- 

 blished and investigated in several particular phases of the 

 phenomena. In the path of physical experimentation, on 

 the other hand, the discoveries which have been made of the 

 relations of terrestrial magnetism to electricity in motion, to 

 radiant heat, and to light ; the recent generalisation of the 

 phaenomena of diamagnetism, and the discovery of the 

 specific property of the oxygen of the atmosphere to acquire 

 polarity, all open to us the cheering prospect of a nearer 

 approach to the nature of the magnetic force itself. 



In order to justify the praise which I have ventured to 

 bestow on the magnetic labours, taken generally, of the 

 first half of the present century, I append a brief notice of 

 the more prominent among them, arranging them sometimes 

 singly in chronologiccil order, and sometimes, where they 

 appear to have called each other forth, in groups. ( 68 ) 



1803 1806. Krusenstern's Voyage of Circumnaviga- 

 tion, 1812. The magnetical and astronomical portion of the 

 work is by Homer. (Bd. iii. S. 317.) 



1804. Examination of the law of increase of the intensity 

 of the earth's magnetic force north and south of the mag- 

 netic equator, founded on observations made from 1799 to 

 1804. (Humboldt, Yoyage aux Regions equinoxiales du 



Nouveau Continent, T. iii. p. 615 623 ; Lametherie, 

 VOL. IY. F 



