150 PHYSICAIi GEOGBAPHY OF THE SEA, AND ITS IMETEOROLOGY. 



broken, they will arrange themselves as in Fig. 2. The earth it- 

 self^ or the atmospheric envelope by which it is surrounded, is a 

 most powerful magnet, and the lines of force which proceed whether 

 from its interior, its solid shell, or vaporous covering, are held ta 



Fig. 1. 



'^\J'- 



llli 



be just such lines as those are which surround artificial magnets ; 

 proceed whence they may, they are supposed to extend through the 

 atmosphere, and to reach even to the planetary spaces. Many 

 eminent men and profound thinkers, Sh David Brewster among- 

 them, suspect that the atmosphere itself is the seat of terrestrial 

 magnetism. All admit that many of those agents, both thermal 

 and electrical, which play highly important parts in the m.eteor- 

 ology of our planet, exercise a marked influence upon the magnetic 

 condition of the atmosphere also. 



347. Now, when, referring to Dr. Faraday's discovery (§ 345), 

 The TBagnetic influ- and the magnetic lines of force as shown by tli& 

 Tthe air a^d^f^e Irou filhigs (§ 346), WO comparo the particles of oxy- 

 spots on the sun. ggj^ gg^g j^q tliesc miuuto bits of fcrruginous dust that 

 arrange themselves in lines and curves about magnets ; when we 

 reflect that this great magnet, the earth, is surrounded by a para- 

 magnetic gas, to the molecules of which the finest atom from the^ 

 filels in comparison gross and ponderous matter; — that the entire 



