176 THE INTELLECTUAL RISE IN ELECTRICITY. 



The next great discovery which Peregrinus notes is the 

 possibility of changing the magnetic poles. "If," he 

 says, "the south part of the iron which has been rubbed 

 by the north part of the stone be forced to meet the 

 south part of the stone; or the north part of the iron, 

 which has been rubbed by the south part of the stone, be 

 forced to meet the north part of the latter, then the virtue 

 of the iron will be altered; and if it were north, it will be 

 made south, and vice versa. And the cause of this is the 

 last impression acting, confounding, or counteracting and 

 altering the original virtue" Unless Peregrinus drew 

 some occult distinction, in his own mind, between the 

 influence of the heavenly sphere upon the magnet and 

 upon the needle receiving its virtue therefrom, it is diffi- 

 cult to perceive why this remarkable revelation of the pos- 

 sibility of destroying or reversing magnetic polarity did 

 not suggest to him that such influence must be of a strange 

 and inconsistent kind if it could be thus neutralized or 

 inverted. But this again is a nineteenth century criticism. 



Peregrinus does see, however, that the poles of the lode- 

 stone are apparently unstable, in a curious sort of way: and 

 he announces that the unlike poles of two magnets come 

 together not only to assimilate, but to unite and make one. 

 Then, to prove this, he cuts a magnet in two and shows 

 that each part has two different poles. And yet, when the 

 parts are brought together to reconstitute the magnet in 

 its original form, the polarity is the same as before the 

 cutting, and two of the four poles which the two frag- 

 ments possessed have seemingly vanished. That is the 

 first announcement of the persistence of polarity in the 

 separated parts of a lodestone, and it was a refutation 

 in advance of the later theory of two magnetic fluids 

 residing only in opposite ends of the stone. The ex- 

 periments 1 are stated in some detail, but, as they amount 



1 In the printed copy of Peregrinus' letter which the British Museum 

 possesses, Dr. John Dee, Queen Elizabeth's favorite astrologer, has cov- 

 ered the pages relating to them with underscorings and diagrams, as if 

 he regarded that part of the work as the most important of all. 



