Bkown — Mechanical Stress and Magnetisation of Nickel. 511 



A fresh No. 16 nickel wire was taken and prepared for experiment in 

 the usual way, without attempting to get any definite degree of hardness ; 

 the heating, liowever, left the wire in a state of magnetic softness lying 

 between Ho and Hj, of our arbitrary scale, judging from the values of the 

 twists subsequently obtained. The length of the wire was 226 cms. ; and 

 the longitudinal load on it during the tests was 0-5 x 10^ grammes per sq. cm.; 

 and four sets of observations were made when the current densities in the 

 wire were 50, 100, 150, and 200 amperes per sq. cm. respectively; the 

 results are shown in Table V, and as curves in fig. 5. 



Magnetic Field H. 

 Fig. d. — Wire with load and length constant and varying current density. 



[Taulk v. 



