QUADKANTAL EFFECT OF INDUCED MAGNETISM. 139 



62. Effect of the combination of two masses of iron, 

 in opposite azimuths : and of two masses of iron, in 

 azimuths differing 90. 



One curious consequence of this law, easily verified 

 in experiment, is, that if a mass similar to the first mass 

 be placed on the opposite side of the compass, carried 

 by the same frame so that in revolution it is always 

 opposite to the first mass, it doubles the disturbance ; 

 but if it is placed afc 90 either to the right or to the left 

 of the original mass, always retaining that relative posi- 

 tion, it neutralizes the disturbance. For, the original 

 disturbance being a sin 20, that of an opposite mass will 

 be a sin 2 (0 + 180) 



= a sin 20, 



the addition of which doubles the first : but the disturb- 

 ance produced by a mass 90 to right or left will be 

 a sin 2 (0 + 90) 



= a sin 20, 

 the addition of which neutralizes the first. 



63. Simplest form of theory for explanation of the 

 phenomena of induction. 



In Figure 51 conceive the first line of circles to 

 represent particles of a mass of iron, or at least so 

 many of the particles as contain united portions 

 of red magnetism and blue magnetism, in a line 

 extending through a mass of iron. And conceive 



