ON MAGNETOSTRICTION. I7 



The curves of the length change are plotted in Fig. 3. 



All the nickel steels indicate increase of length in fields up to 

 about H='2000. The character of the change for 4:6% ^i resem- 

 bles that for nickel with opposite sign, inasmuch as the curve of 

 elongation has great similarity to that of magnetization. The 

 elongation in very weak fields takes place slowly, but in fields of 

 about 30 units, the rate of change is most rapid and soon reaches an 

 inflexion point, after which the increase in length takes place only 

 very slowly and in an asymptotic manner. 



With the 36% Ni, we observe similar features in the curve of 

 elongation. The inflexion point lies in higher field, but the elonga- 

 tion is less than in 46% alloy. After this stage is passed, the 

 ovoid o^oes on increasins: in leno;th at an almost constant rate, which 

 is greater than for 4:6% Ni. Although the field, at which the curves 

 for 46% and 36% Ni intersect has not yet been reached, we can easily 

 infer that if the field be sufiiciently increased, the elongation in o6% 

 Ni, which is the least expansible by rise of temperature, will exceed 

 that for 46% Ni. The contrast between 4:6% and 36% Ni is similar 

 to that between 36% and 29%, so that what has already been remarked 

 with respect to the two former alloys, equally applies to the relation 

 between the two latter metals. It is also remarkable to observe that 

 the 29% Ni, which will apparently indicate the largest increase in 

 length, if the field be made sufficiently strong, is the least susceptible 

 of the three nickel steels. AVith the 25% Ni, we could not detect 

 any change, Avhich is within the scope of measurement now attainable 

 with the present arrangement. 



The nickel steel wires, in the annealed state, present changes in 

 length as similar to those of the ovoids. In the hard drawn state, 

 the change is decidedly less than in the annealed. 



