GEOLOGY. 161 



of iron, renders it therefore magnetic ; thus electricity, 

 unequal calefaction and a blow, whereby it is thrown into 

 a state of vibration. An iron bar planted perpendicu- 

 larly becomes magnetic, because it is then a radius to the 

 earth. From the same reason it becomes magnetic, if 

 placed in the magnetic meridian. 



e. TERRESTRIAL MAGNETISM. 



771. If all metals are in idea magnetic ; so must the 

 metallic veins, as products of magnetism, be magnetic 

 lines. Every vein has a north and a south pole. 



772. As every vein is a magnetic line or magnetic 

 needle upon a large scale ; so must two veins abutting 

 against each other represent likewise a magnetic tension. 

 A mountain of ores is a net of numerous magnets inter- 

 lacing each other. As one vein is related to the other, so 

 must one metalliferous mountain be related to the other ; 

 and thus two mountains of this character stand in mag- 

 netic polarity with each other. The whole earth is sur- 

 rounded by a magnetic i^et. 



~^773. As every metal, every vein, every rock is in 

 miniature a magnet, so must the earth be a magnet 

 upon a large scale. There is a Terrestrial magnetism. 



774. This magnetism belongs only to the earth only 

 in so far as it possesses a metallic quality, for magnetism 

 is only the spirit of the metals, not of the other terres- 

 trial bodies, as the earths, Inflammables, and salts. 



775. Magnetism is no general character of the earth, 

 still less of the whole solar system, except in so far as 

 the metallic principle lies at the basis of every thing 

 earthy. Magnetism does not operate outwardly over the 

 earth. 



776. The determinants of terrestrial magnetism are 

 the metallic veins, or the metallic beds in the crust of the 

 earth. 



777. Terrestrial magnetism has not been produced or 

 determined by a magnetic nucleus ; since a metal in the 

 middle of the earth is a contradiction. All determina- 



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