BIFILAR MAGNETOMETER. 195 



assumed position of the points of attachment : Figure 

 57 is an end view. These views shew that the two 

 wires are not in one plane: (the angle of crossing is 

 very much exaggerated in the diagrams.) Figure 58 



Fig. 58. 



represents the view from above, or the projection 

 of the whole upon a horizontal plane: this will 

 give the means of computing the torsion-strain pro- 

 duced by the weight of the magnet. 



Let the distance EF of the upper points of attach- 

 ment be 2a, and the distance GH of the lower points 

 be 26 : and let them make the angle </> : also, let the 

 length of each suspension- wire be l\ and the weight 

 of the magnet W. The torsion of each cord will be 



W 



sensibly ; and the resolved part of this in the direc- 

 & 



tion EGf, Figure 58, will be ^ ; and the momen- 

 tum of this to turn the magnet will be 







KL being the perpendicular from K upon EG. But 



132 



