12 AKT. Il -li. NAGA0KA & K. HONDA. 



50xl0 -6 in a "field of 1600 Gauss. We noticed a slight decrease 

 of volume for 70.32 per cent Ni. specimen in weak fields. 



Plotting the volume change in constant fields (Fig. (>) against 

 the percentage content of nickel, we notice a sudden ascent for 25 per 

 cent to 29 per cent, and then a sudden descent to about 40 per cent. 

 The decrease in the volume change becomes gradually less as the alloy 

 approaches pure nickel. 



On several occasions, we have remarked that the volume change 

 by magnetization is of a differential nature, since 



Volume change in ovoid = elongation parallel to magnetization. 



+ 2. elongation perpendicular to magnetization. 

 Generally, the elongation in the direction of magnetization is of opposite 

 sign to that in the direction perpendicular to it. In iron and nickel, 

 the sum of these elongations representing the volume change nearly 

 vanishes, while in nickel steels, this is by no means the case. The sum 

 of these respective elongations is maximum in 29 per cent Ni., in which 

 the position of maximum effect is very prominent. The phenomenon 

 is the more remarkable as this point nearly coincides with the corre- 

 sponding points for magnetization and elongation by magnetization. 

 The border line which marks the transition of nickel steel from acier 

 dur to acier doux is also little short of the same percentage, which will 

 probably explain the existence of the maximum change of volume, 

 considered as a differential effect. 



Connexion villi other physical properties of nickel steel. — When we 

 examine various other physical properties of this valuable alloy, we 

 cannot but be struck with the singular coincidence of the changes 

 attending the magnetization in the neighbourhood of 29 per cent Ni. 

 with those attending the elastic and thermal behaviour as the metal is 

 transformed from acier dur to acier doux. Vor the said percentage con- 

 tent of nickel, the resistance to rupture is least, but the elongation on. 



