ON MAGNETISM. 



ends. (The words, from their brevity, and their appli- 

 cability to the colour of the paint put on magnets, are 

 convenient : it has long been the custom of tradesmen 

 to paint with red the north-seeking end of a magnet.) 

 In the diagrams, the red end will be distinguished by a 

 cross-hatching and the blue end by a longitudinal 

 hatching. (It is usual for tradesmen to mark the north- 

 seeking end by a transversal file-mark.) 



Introductory Diagram explaining the representations 

 of Magnets. 



Poles of Ked Magnetism, seeking the North. 



Poles of Blue Magnetism, seeking the South. 



A horse-shoe magnet is merely a straight magnet 

 bent into the horse-shoe form : it will be shewn here- 

 after that the properties of the two ends differ in the 

 same manner as those of the ends of a straight magnet. 



8. Method of magnetizing steel bars, and of preserv- 

 ing their magnetic power. 



It is not easy to say how artificial magnets were 

 formed in the first instance. Probably they may have 

 been derived from the natural magnet ; whose attrac- 

 tive properties, and whose power of producing temporary 



