306 



If the sample has the form of a thin slab normal to the lines 

 of force 



B,-l=~ — —^ . . . (17") 



l + 2<7 q' 



Space lattice of spherical holes. 

 From (J 4") we get for this case to within the second power 



of («o-ir 



g — \ ■::2i j 



i+f;^-i)-p5-y(N-i)' 



where p' is the same function of h as c[. The corresponding formula 

 for the space lattice of spheres is 



i+|(«.-i)-|(«.-ir 



The term ^ thus tends to reconcile the two expressions. However 



for the case of touching spheres or touching holes the space lattice 

 of holes has a higher e than the space lattice of spheres even though 

 q is made the same for both. This means that the continuous path 

 of the flux between the holes contributes to a high value of the 

 effective g. It thus becomes apparent that q and e, alone do Jiot 

 suffice to determine g even if the structure is on the average isotropic. 

 The correction in (e, — 1)' ma}' therefore be never applied with 

 certainty and an estimate of its amount is all that the present theory 

 can offer. 



SUMMARY. 



1. The consideration of the effects of the demagnetizing field for 

 various models of the powder shows that to within the first order 

 terms the correction is the same for all models considered and may 

 be expressed by the fact that the force on a sphere of the powder 

 is equal to the force which would be exerted on the material if it 

 were moulded into a solid sphere instead of being powdered. 



2. Different models give results differing in the second order terms 

 in the demagnetizing field. 



