[ 35 ] 

 CHAP. VI. 



OF MAGNETISM. 



Of natural and artificial Magnet's. -Magnetic Powers. Attra8ion> 

 -"-Re tuition. Polarify.* Declination. Dipping of the Magnetic 

 Needle. Communication oft.be Magnetic Power. 



* I ^ H E properties of the magnet are illuftrative of* 

 JL fo many principles and laws of nature, that 

 though, perhaps, not ftriftly in order, I have deter- 

 mined to introduce the fubjeft before the conclufion of 

 this preliminary book ; as fome occafions may fhortly 

 occur, when a reference to this topic may probably be 

 ufeful, if not abfolutely neceilaiy. 



It is well known that every magnet is a ferrugineous 

 body, and that its attractive force is confined in a great 

 meafure to ferrugineous fubftances. Magnets are of 

 two kinds, natural and artificial. The natural mag- 

 n'et or loadftone *, is a bog ore of iron ; artificial mag- 

 nets are formed either by being touched with a natural 

 magnet, or by other different prccefles., which will pre- 

 fently be explained. 



The properly magnetic ores are calciform (refem- 

 bling a calx or cinder) and are moflly of a dull 

 brownifh black j-. There are reddifli magnt ts found 

 in Arabia ; but mod of thofe in Europe refemble 

 wrought iron in colour. Their hardnefs is juft furB- 

 cient to afford fparks with a fteel, and they are with 

 difficulty attacked by a file. They differ considerably 



* Load (Sax.) or leading flonc, probably from its being a guide 

 to mariners. Adams on Mag. p. 377. 



f Kirwan's Min. and Cavallo on Magnetifm, 



D 2 in 



