40 



FIEST YEAR SCIENCE 



opposite end of the magnet the opposite end of the needle 

 dipped. This same action is found when a magnetic 



needle is carried from north to 

 south upon the earth. If a 

 needle is carefully balanced and 

 then magnetized, it will be 

 found no longer to assume a 

 horizontal position. 



In the northern hemisphere 

 the north end will dip and in 

 the southern hemisphere the 

 south end. In the northern 

 hemisphere it is customary to 

 make the south end of the 

 needle a little heavier so that it 

 will stay in a horizontal posi- 

 tion. At the magnetic pole 

 the needle would stand verti- 

 cal. If a needle is accurately 

 balanced on a horizontal axis 

 and then magnetized, it will show the angle of dip in any 

 locality. Such a needle is called a dipping needle 

 (Fig. 15). 



20. The Mariner's Compass. In the 

 ordinary mariner's compass a magnetic 

 needle is arranged so that it will swing 

 freely in a horizontal plane. A circu- 

 lar card is divided into four equal parts 

 the dividing lines of which are marked 

 with the cardinal points of the compass, 

 the intervening spaces being divided 

 into eight equal divisions. The card is attached to the 

 needle and inclosed in a box called the binnacle. This 

 box is arranged so that it will always remain horizontal. 



Fig. 15. 



Fig. 16. 



