MAGNETlZATlOxX AND MAGNETIC CHANGE OF LENGTH. 



29 



NICKEL STEEL 24.04^ 



The efîëct of cooling on the magnetic elongation in nickel 

 steels is exactly parallel to the same effect on magnetization. In 

 nickel steels containing percentages of nickel greater than 28.74^, 

 the elongation is diminished in weak fields and increased in the 

 strong, by cooling them in liquid air ; with other nickel steels, 

 the initial decrease of elongation vanishes. 



The ratio of the elongation in liquid air to that at ordinary 

 temperature increases in strong fields, as the percentages of nickel 

 decreases. In 36?^ Ni, it amounts to about 1.6 in H =500 

 C.G.S. ; and in 28.32^/^ Ni, to 3.7, and in 24.40^/ Ni to 160 for 

 the same field. 



For reversible nickel steels, the elongations after and before 

 cooling coincide with each other. The elongation of other nickel 



