302 M.\(,\I:TI>M 



where / is the distance between the p -1 iil tend to make 



the needle dip in the direction of I. But the m-rdle max In- 

 horizontal at a place in the Northern magnetic hemisj 

 putting c towards the N end of it a dMaiuv t'rom (i Mich thai 

 is the weight of the needle zr.fG = wA7. The needle will tlun 



rnH 



rn 



rn 





w 



Fie 



remain horizontal even \\hen displaced from thi 



for the only other forces acting on it are mll IMH i/,,nt.il When 



so displan d i hoe forces will form a c-onp 



iit(dk- into the ina^netir meridian, ami it \\ill ultimately M-ttK- 



tiirn-. Kvcn it c i> not acvurahK jla. . 



needle will still settlr in tin- plain- <>t th< magnetic uu-ridian. 



I^et us Mippo.se that it m i^radua 



of which c is the ccntiv. and that \\t- knw tin- .U'-o^ra; \.rth 



point on this circle ; il\ioiisly the dtu-lination 

 circle between this point and the N end ol 



111 practice the magnet ic axis cannot 1 



with the axis of figure, \N 



ra H 



axis from the position^ of the a\ ;f the in tii>t 



suspended with one face npuanU, and is then turned over and 

 suspended with the other face upwards. Let (a), Fig. 223, be a 

 plan of the needle in the first case. We read the direction of AB 



