100 



<J> 



1, 



M, 

 0, 

 0, 



o, 

 o, 

 o, 

 o, 



Prof. A. W. Riicker on the Magnetic 



«ro> — lj —dm, 



MN« m; —fJbm, flm'SaCm, 



0, 1, «» r i» 



0, fi m -/i m Na m _i, 



0, 



— a 



= <£ A< 



This may be written 



<E> 



OL 



M 



M, 

 M, 



0, 



o, o, 



0, 0, ^N ai 



0, 0, «o 



0, 0, -AtiN« 



M, -M, 



■MN, -fji m , 



o, i, o 



o, 



0. 



•/*iN«o 



<£oA; 



whence, by subtracting the first from the second row, 



<£> 



a, 



M 



M, M, -M 



0, -M(N + 1), M-/* m , 



0, 



0, 



0, 







o, 



0, . . . — ^NOq 



= </><A 



.-. -^(N + IJM 





= <£ A. 



0, 0, 0, . . . -^Na 



Proceeding in the same way with the new determinant, 

 we finally get : — 



{-(N + l) m+1 4)a m a w _ 1 a M/^ w _i fr = (£ A. 



Next, putting <E> = 0, we get in like manner 



M^A = {— (N + l)} m+1 ^o a m«m-l .... «o/Wm-l • • • • fWotyo 5 



Hence if M=^ > *• *• if the permeabilities of the enclosed and 



