MAGNETS. 193 



dipping needle makes with a horizontal line is called 

 its inclination or dip. At the magnetic poles the 

 inclination is 90; at the magnetic equator there is no 

 inclination. The inclination at any given place is not 

 greatly different from the latitude of that place. 



319. Declination or Variation. The magnetic 

 needle, at most places, does not lie in a north and south 

 line. The angle which the needle makes with the 

 geographical meridian is its declination or varia- 

 tion. A line drawn through all places where the needle 

 points to the true north is called a Line of no Variation. 

 Such a line, nearly straight, passes near Cape Hatteras, 

 a little east of Cleveland, through Lake Erie and Lake 

 Huron. It is now slowly moving westward. At all places 

 east of the Line of no Variation, the end of the needle 

 points west of the true north ; at all places west of the 

 Line of no Variation, the variation is easterly. The fur- 

 ther a place is from this line, the greater the declination 

 it being 18 in Maine and more than 20 in Oregon. 



320. Magnetization. A common way of magnetizing a 

 steel bar is to draw one end of a strong magnet from one end of the 

 bar to the other, repeating the operation several times, always in the 

 same direction. A second method is to bring together the opposite 

 poles of two magnets at the middle of the bar to be magnetized, and 

 simultaneously drawing them in opposite directions from the mid- 

 dle to the ends. A third method, represented in Fig. 132, is known 

 as "the double touch." The opposite poles of two magnets are 

 kept at a fixed distance from each other by means of a wooden block 

 placed between them. The magnets thus held are moved from 

 the middle toward one end of the bar, thence to the other end, 

 repeating the operation several times, and finishing at the middle 

 when each half of the bar has received the same number of fric- 

 tions. But better than any of these can give are the effects produced 

 by electro-magnetism. ( 394) 



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