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MR, G. T. WALKER OK REPULSION AND ROTATION 
Thus (i.), when h (b -f- b')} is positive, and greater than d/6 the couples are both 
negative. 
Eig. 18 . 
(ii.) When 6h is numerically less than d, the signs are . 
(iii.) When 6h is negative and numerically greater than d, the couples are both 
positive. 
Pig. 21. Fig. 22. 
If we take two spherical shells in the presence of a small magnet of moment 
K cos pt , whose axis cuts the line joining the centres of the spheres at angle a, we find 
for the couple on the a, b shell 
~ K 3 
2,l'jr‘p }, oda i crcr l . 
2A, a', ,<vv s * ( “’ y ’ 7)( 
where </> (a, y, y) is written for 
