54 HISTORY OF MAGNETISM. 



iron have the magnetic virtue, though in a weaker 

 degree than the magnet itself 8 , and he asserted 

 distinctly that the magnet is merely an ore of iron, 

 (lib. i. c. 16, Quod magnes et vena ferri idem sunt.) 

 He also noted the increased energy which magnets 

 acquire by being armed ; that is, fitted with a cap 

 of polished iron at each pole 9 . But we do not find 

 till a later period any notice of the distinction 

 which exists between the magnetical properties of 

 soft iron and of hard steel ; the latter being sus- 

 ceptible of being formed into artificial magnets, 

 with permanent poles ; while soft iron is only pas- 

 sively magnetic, receiving a temporary polarity from 

 the action of a magnet near it, but losing this 

 property when the magnet is removed. About the 

 middle of the last century, various methods were 

 devised of making artificial magnets, which exceeded 

 in power all magnetic bodies previously known. 



The remaining experimental researches had so 

 close an historical connexion with the theory, that 

 they will be best considered along with it, and to 

 that, therefore, we now proceed. 



8 Lib. i. c.9 13. 9 Lib. ii. c.17. 



