FIQ. 109. 



A magnetized needle or 

 bar takes a N-S position. 



CHAPTER VIII 



MAGNETS AND ELECTRICITY 



135. Magnets. It was known to ancient peoples that 

 certain specimens of iron ore could draw to themselves 

 bits of iron or steel. These specimens came to be called 

 magnets, from Magnesia, in Asia Minor, 



where they were found. Natural mag- 

 nets are also called lodestones, from 

 "lode/' a vein of 

 iron. When a lode- 

 stone is suspended 

 so that it can move 

 freely, it points north and south. 

 If a bar of steel is rubbed with a lode- 

 stone, it becomes magnetic itself, and 

 likewise points north and south when 

 suspended (Fig. 109) . A slender mag- 

 netized needle or bar is the essential 

 part of a mariner's compass. The _ ^^ 

 compass was known before the days of lEU-- -^*3f 

 Columbus (Fig. 110). FIG . m . 



Each end of a magnet 

 attracts iron filings. 



136. The Poles of a Magnet. If a 



magnetized steel knitting needle is dipped into iron filings, 

 the filings are attracted by the needle only at its ends 

 (Fig. 111). If the needle is broken in two, each piece is a 



125 



FIG. 110. 



The Thirty-two "Points" of 

 a Mariner's Compass. 



