§347. 



EASTING OF THE TRADE-WINDS, ETC. 



151 



Fig. 1. 



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Fig. 2. 



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self, or tlie atmospheric envelope by which it is surrounded, is a 

 most powerful magnet, and the lines of force which proceed wheth- 

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

 to be just such lines as those are which surround artificial mag- 

 nets ; 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. Sir David Brewster 

 among them, suspect that the atmosphere itself is the seat of ter- 

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

 thermal and electrical, which play highly important parts in the 

 meteorology of our planet, exercise a marked influence upon the 

 magnetic condition of the atmosphere also. 



347. Kow, when, referring to Dr. Faraday's discovery (§ 845), 

 The magnetic influ- ^^^l thc maguctic liucs of forcc as shown by the 

 oJ^lairanJrffhe i^on filings (§ 346), wc compare the particles of ox- 

 ppots on the sun. ^^^^ g^g ^^ ^j^ggg j^inutc bits of fcrrugiuous 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 file is in comparison gross and ponderous matter— that the en- 

 tire mass of this air is equivalent to a sea of mercury covering the 

 earth around and over to the depth of 30 inches, and that this 



