CHAPTER XXXIII 



MAGNETS AND CURRENTS 



304. In the twelfth century, there was introduced into 

 Europe from China a simple instrument which changed jour- 

 neying on the sea from uncertain wandering to a definite, safe 

 voyage. This instrument was the compass (Fig. 221), and be- 

 cause of the property of the compass 

 needle (a magnet) to point unerr- 

 ingly north and south, sailors were 

 able to determine directions on the 

 sea and to steer for the desired 

 point. 



Since an electric current is prac- 

 tically equivalent to a magnet (Sec- 

 tion 296), it becomes necessary to 

 know the most important facts 

 relative to magnets, facts simple in 

 themselves but of far-reaching 

 value and consequences in electric- 

 ity. Without a knowledge of the magnetic characteristics of 

 currents, the construction of the motor would have been 

 impossible, and trolley cars, electric fans, motor boats, and 

 other equally well-known electrical contrivances would be un- 

 known. 



305. The Attractive Power of a Magnet. The magnet best 

 known to us all is the compass needle, but for convenience 



328 



FiG. 221. The compass. 



