MAGNETISM. 419 



lu what posi- 789. When a magnet is supported in such, 

 net" rreeiy^sut ^ ^^7 ^^ to movc freely, it will rest only in 

 pendedrest? q^q position, viz., with its poles, or extremi- 

 ties directed nearly north and south. 



If drawn aside from this position, it will continue to 

 vibrate backward and forward, until it again rests in the 

 game position. 



^^^^ are th "^^^ polc, or cxtrcmity of the magnet thrl; 



north and south constautlv points toward the north, is called 



poles of a mag- •' ^ ' 



net? the North Pole, and the one that points to- 



ward the south, the South Pole of the magnet. 



790. That property of a magnet which will 

 What, is mag- causc it, wlicn suspended freely, to constantly 



netic polarity ' i: J ' •' 



or directive tum tho samo part toward the north pole, 



power r . r j 



and the oj)posite part toward the south pole 

 of the earth, is termed magnetic polarity, or directive 

 power. 

 ^^ . When a mas-net, being free to move, places 



when IS a mag- . _ . . 



net said to tra- itsclf after dcflcction in a nearly north and 



verse? , ,. . . 



south line, it is said to traverse. 



The attractive force of the loadstone, or natural magnet, can not be consid- 

 ered as of any great amount. Native magnets, in their rude state, will sel- 

 dom lift their own weight, and, with some rare exceptions, their power ia 

 limited to a few pounds. 



791. When two bodies possessing magnetic 



What is the . ^ . ^ ^ . , 



general law of properties are brouo-ht near, or in contact with 

 tractions and cach Other, the like poles will repel, and the 



repulsious? ,., , ■"■ '■ 



unhke attract each other. 

 Thus, the north or the south poles of two magnets re- 

 pel each other ; but the north pole of the one will attract 

 the south pole of the other. 



792. Magnetism may be excited most read- 

 in what sub- .,..'-', , ^ 



stances may ily m irou aud stecl. lu stccl tho magnetic 



ma,'nuti,sm be "^ i • i i • 



most easily ex- property, w^icn induced, remains permanent; 

 but soft iron loses its power as soon as it is re- 

 moved from the influence of the exciting magnet. Brass^ 

 nickel, and cobalt may also be rendered magnetic. 



