18 



AKT. 8.— H. NAGAOKA AN'D K. HONDA : 



The curves of the length change in iron or nickel, placed side by 

 side with those in nickel steel, present a singular contrast. As is well 

 known, nickel contracts, instead of expanding as in iron, the amount 

 of contraction being several times that of iron. The feature here pre- 

 sented by nickel steel is similar to nickel as regards the amount and 

 the character of the change, but as to the sense of elongation, it is 

 similar to iron in weak fields increasing instead of diminishing as in 

 nickel. It thus appears that the length change by magnetization is 

 not of a simple nature, and not to be easily determined from the per- 

 centaofes of the constituent metals. 



{e) Nickel steel wires in low fields (Fig. -1, PL I.). 



Urged by the questi(jn of the practical utility of the metal, we 

 made special investigations into the change of length in low fields, 

 such as may habitually occur in the neighbourhood of electric installa- 

 tion or in terrestrial magnetic field. The question will be of utmost 

 utility in deciding the effect of the terrestrial field ; as one instance, 

 we may mention that in using Jaderin's wires of nickel steel in 

 geodetic measurements. One may wonder from what has already 

 been described, if the effect of the magnetic field will not be of the 

 same magnitude as that of thermal expansion, which, as is well 

 known, is of very minute amount. Our results for low fields 

 are as follows : — 



