28 Mr. R. L. Wills on the Effects of Temperature 



Representing the results of experiment given in Table III. 

 by plotting permeability with respect to temperature for 

 fairly strong fields, the changes in the permeability shown in 

 figs. 12 and 13 are seen to take place comparatively suddenly, 

 the curves showing points of maximum permeability at tem- 

 peratures about 400° C. and 590° C. 



The relative values of the permeability at these maximum 

 points vary with the field. For magnetizing forces below 

 about 1 c.G.S. the maximum permeability occurs at tempera- 

 tures near the critical point, as in the case of iron. Under 

 forces between about 1 C.G.s. and 2*6 C.G.S. the maximum 

 permeability occurs at the higher maximum point, that is, at 

 about 590° C, and with magnetizing forces above 2*6 c.G.s. 

 the maximum permeability is reached at about 400° C. 



This lower maximum point agrees very closely with that 

 found by Richardson*. 



5 per cent. Nickel Alloy. 



Various investigations have shown that steels containing 

 certain percentages of nickel possess remarkable physical 

 properties. Hopkinson f investigated the effect of tempe- 

 rature on the magnetic properties of a steel containing 

 5 per cent, nickel, and gave curves showing the change in 

 induction with respect to temperature for different magnetizing 

 forces. At the ordinary temperature of the room the maxi- 

 mum magnetization of this specimen was greater than that 

 of wrought iron. 



Experiments of the same nature as those described above 

 were made on a steel containing about 5 per cent, nickel to 

 see the effect of temperature on the permeability in each of 

 the stages of the magnetizing process, and to ascertain the 

 relation between temperature and magnetic force in bringing 

 on the successive stages. 



The dimensions of the ring were as shown: — 



H 



— 7- 67 cms 



— ^ 



0-66 



c 2-57 



V 





* Phil. Mag. Jan. 1900, p. 137. 



f Proc. Roy. Soc. vol. xlviii. p. 6 (1890). 



