32 ART. 8.-H. NAGAOKA AND K. HONDA: 



2. In cobalt, the character of the change is différent in the cast 

 and in the annealed state. 



(a) Cast cobalt contracts in low fields and attains the minimum 

 leno-th in IT=loO. whence it returns to its former leno-th in H=750, 

 and goes on elongating at a slow rate, as the field is increased (re- 

 sult already obtained by liidwell). This stands in reciprocal relation 

 with the effect of mechanically elongating cast cobalt on magnetiza- 

 tion. 



(A) Annealed cobalt contracts without showing a minimum 

 length up to 7^=1800. The character of the change is similar to that 

 of iron after passing the maximum elongation. This stands in 

 reciprocal relation with the effect of mechanically elongating annealed 

 cobalt on magnetization. 



o. Xickel steel elongates by magnetization. The character of 

 the chano-e is similar to that of nickel, but the sense is different. The 

 rate of change {-ttt) i^^ high fields is greater in 29% Xi than in 36% 

 Ni, in which it is again greater than in 46% Ni. The amount of the 

 change is in inverse order up to H=2000. 



Nickel steel elongates to a greater degree in the annealed than in 

 the hard drawn state. 



4. The elongation of nickel steel in very low fields (comparable 

 with the terrestrial magnetic field) is generally less than 10"^ 



Change of \'olnine In/ Magnetization. 



1. Iron, steel, and nickel show increase of volume by magneti- 

 zation, but cobalt (cast and annealed) shows contraction. 



2. (rt) Cast cobalt contracts at a rapid rate in low fields, but 

 above iî= 100, the rate becomes less and the contraction reaches a 

 maximum in H=dOO, whence to return gradually with further in- 

 crease of the field. 



