RESEARCHES ON MAGNETOSTRICTION. 



387 



as for the length change. The experimental verification of these 

 conclusions will involve considerable difficulty. 



Besults in iron. — The experimental and theoretical results arc 

 widely discordant in iron- Making use of the measurement of strains 

 in the ovoid caused by magnetization, we find the following numbers 

 for le and ¥ :— 



Table. 3. 



The above table shows that ¥ and k" are of the same order of 

 magnitude as for nickel ; they are, however, for the most part of opposite 

 sign. The approximate relation h'-\ — q— =° does not llom f° r n ' on > 

 the quantity /> ; ' + ^- amounting to several thousands in low fields. Il 

 would therefore appear that the effect of hydrostatic pressure is 

 considerable, which is irreconcilable with the experiments already 

 cited. For the value- of à I in the 7th column, we see that for the 

 small elongation, there is rapid increase of magnetization in low fields, 

 which ultimately reaches the maximum in H=\0 nearly ; this point 

 evidently coincides with the Villari critical point. The magnetization 

 then begins to diminish very slowly bu! continuously till it becomes 

 less than in (he unstrained stale. This theoretical conclusion agrees 



