176 The Rev. H. Lloyd on the mvtucU Action of permanent Magnets. 



and substituting, 



sin* a cos a = ^^ P ; 



from which the angle a is determined. This arrangement is represented in 

 Fig. 7. 



The conditions of equilibrium are here satisfied independently of Q. As 

 to P, it cannot exceed the limit determined by making the first member of 

 the preceding equation a maximum. This gives tan a ■=. 2; and, for the 

 greatest value of P, ^^^^ = 3.155. 



