MAGNETISM". 307' 



selves with creeping round the coasts. In the 

 night, and when necessity obliged them to lose 

 sight of the shore, their only guides were the 

 heavenly bodies. 



While navigation continued so dangerous, men 

 never would have ventured upon such voyages as 

 those to the West Indies, America, and the South 

 Seas, and probably the existence of those countries 

 would have been still unknown to us. We cannot, 

 therefore, think too highly of this extraordinary 

 instrument, which has so much enlarged our stock 

 of knowledge, and procured for us so many new 

 enjoyments. 



The natural loadstone has the quality of com- 

 municating its properties to iron and steel; and 

 when pieces of steel properly prepared are touched 

 (as it is called) by the loadstone, they are deno- 

 minated artificial magnets. 



These artificial magnets are even capable of 

 being made more powerful than the natural ones ; 

 and as they can be made of any form, and con- 

 sequently are more convenient, they are now uni- 

 versally used. 



All magnets, whether natural or artificial, pos- 

 sess the following properties. 



They all attract iron. 



When a magnet is placed so as to be at liberty 

 to move freely in every direction, it turns so that 

 its ends point towards the poles of the earth, or 

 very nearly so: and each end always points to the 

 same pole. This is called the polarity of the mag- 

 net: the ends of the magnet are called poles, and 

 they are called north and south poles of the mag- 

 net, according as they point to the north or south 

 pole of the earth. When a magnet places itself in 

 this direction, it is said to traverse. 



