[ i89 J 



and the upper a fouth pole. In the S. hemifpheie the under 

 end becomes a fouth pole. 



A EAR of iron not previoufly magnetic does not acquire this 

 difpofition in the flighted degree while lying in a horizontal or 

 nearly a horizontal difpofition, but if one end of it be raifed it 

 immediately acquires it in fome degree, as appears by ajiproach- 

 ing a magnetic needle to either end, becaufe in that diredlion it 

 is then expofed to the adivity of the polar ends of the great 

 general m.agnet. 



But if a bar of iron be heated, though only at one end, and 

 while hot fet in a vertical or nearly a vertical pofition, it will 

 acquire the magnetic power much more readily. 



So alfo if one end of a bar of iron not magnetic be ftruck 

 againfl the ground it will become in fome degree magnetic, the 

 lower end becoming a north pole, &c. and if afterwards the 

 other end be ftruck in the fame manner the poles will be re- 

 verfed. 



Hence it is evident that any motion communicated to the inte- 

 grant particles of iron placed in a proper fituation helps them 

 to aflume the magnetic difpofition already impreflfed upon them 

 by the great general magnet. 



If the oppofite poles of two magnets of equal power be ap- 

 proached to each other the power of both is increafed ; and 



if 



