48 THE INTELLECTUAL RISE IN ELECTRICITY. 



magnetic current flowing through the rings and its effect 

 exerted upon the space around the magnet is also drawn, 

 for in addition to the continuing current, Lucretius says 

 that there streams from the stone "very many seeds, or a 

 current, if you will, which dispels, with blows, all the air 

 which lies between the iron and the stone," thus produc- 

 ing, as he imagines, a vacuum in front of the iron, into 

 which the air pressure "thrusts and pushes it on, as the 

 wind a ship and its sails ;" and on this theory he accounts 

 for attraction. Furthermore, as Lucretius describes his 

 "streams" as continuously circulating around the lode- 

 stone, the vortex magnetic theory of Descartes is here 

 curiously foreshadowed, if not actually suggested. 



Up to this time, as we have seen, there is nothing in the 

 ancient authors indicating any knowledge by them of the 

 repulsive effect of the magnet. It is always spoken of as 

 drawing the iron. When, however, two magnets are 

 brought together, attraction occurs only when their &;zlike 

 poles are presented to one another the north pole attract- 

 ing the south, and vice versa. But if like poles are 

 approximated, just the opposite result happens, and the 

 magnets mutually repel. It is immaterial whether two 

 lodestones, or one lodestone and a magnetized piece of iron, 

 or two magnetized pieces of iron, such, for instance, as 

 two compass needles, be employed ; the result is always 

 the same. Hence, as iron that has been brought into con- 

 tact with the lodestone (as was the case with the Samo- 

 thracian rings) very readily becomes magnetized by 

 induction from the stone, it is evident that there was a 

 possibility of two rings having become magnetized in this 

 way, being accidentally approximated with their like poles 

 facing one another, and under conditions when one or the 

 other of them might be free to move under the repulsive 

 force. Whatever may have been observed as to this at an 

 earlier time is not known ; but an unmistakable and, prob- 

 ably, the first recorded recognition of the phenomenon ap- 

 pears in the poem of Lucretius. 



