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PROFESSOR J. A. EWING AND MR. G. C. COWAN 



After the same piece of wire was annealed, a precisely similar set of experiments 

 was made, with results which are given below, and shown in fig. 4. 



ANNEALED Nickel Wire. 



To exhibit more fully the effect which the presence of tensile stress has in reducing 

 the magnetic susceptibility of nickel, the same piece of wire (namely, that of the full- 

 line cycle in fig. 2) was again tested under various loads ranging from to 12 kilos. 

 The results are shown in fig. 5, Plate 16, and from the curves drawn there the 

 following values of the maximum susceptibility K have been measured : 



The value of $ which corresponds to the maximum of susceptibility becomes higher 

 as the load is increased ; with 12 kilos., in fact, the maximum appears not to be reached 

 even when < is 115. By comparison with the full-line cycle of fig. 2, the no-load test 

 in this group shows that the wire had lost some of the susceptibility given by 

 annealing, probably because the load of 12 kilos, which had been applied after the 

 cycle of fig. 2 had been completed, and before these observations were made, had 

 produced a slight permanent hardening effect. 



To examine the effects of applying and removing stress in a constant magnetic 

 field another piece of the same nickel wire was softened by heating, and was then 



