660 



Messrs. K. Honda and S. Shiinizu 



the descending temperature is only 20 C.G.S. for a temperature 

 of W° 0., but it amounts to 200 for 20° 0., and at -60° C. 

 it increases to 790. Thus the magnetization o£ the specimen 

 displays a remarkable difference between the ascending and 

 descending branches of the curve. 



The above manner, in which the magnetization is changed 

 by temperature, is common to all other irreversible nickel- 

 steels. As the percentage of nickel decreases, the concave 

 portion of the ascending branch becomes fainter and fainter ; 

 and with 24'40 per cent, and 2404 per cent. Ni, it almost 

 vanishes for strong fields. Apparently, the forms of the two 

 curves for nickel-steels of 29'24 per cent, and 24"04 per cent. 

 Ni are widely different from each other ; but if we compare 

 the forms of the curves of two consecutive nickel-steels, we 

 can trace transition stages from one form to the other. 



The critical temperatures of the alloys for H = 400 C.G.S. 

 are given in the following table : — 



Alloys 



29-24 

 p. cent. 



29 

 p. cent. 



28-74 

 p. cent. 



28-32 

 p. cent. 



26-64 

 p. cent. 



24-40 

 p. cent. 



24-04 

 p. cent. 



Ascending branch . . . 



530°O. 



530°O. 



530°C. 



510°C. 



510°C. 



580°C, 



520°O. 



Descending branch . . . 



70 



140 



80 



50 



10 



130 



40 



Thus, in the ascending branch, the critical temperatures of 

 these irreversible nickel-steels are nearly equal, except with 

 the last but one. The above numbers fairly coincide with 

 those obtained by M. Osmond, except with 24*40 per cent. 

 .Ni. With this alloy the critical temperatures are greater, 

 in our case, by about 50° C. for the ascending branch and 

 100° C. for the descending, than in the experiment by 

 Osmond. The values given by L. Dumas for the first four 

 of these alloys are considerably less than those obtained by 

 us ; but for the remaining alloys the contrary is the case. 

 These discrepancies may probably be due to the previous 

 history of the alloys. 



It remains to mention a singular phenomenon. If at a 

 point in an ascending branch of the temperature-cycle, the 

 temperature be reduced to the ordinary, the path is utterly 

 different from the ascending one. If, however, the tem- 

 perature be again increased to its former value, the path 

 nearly coincides with the former one ; the further increase 

 of temperature diminishes the magnetization in such a 

 manner that the magnetization is not interrupted by the 

 cooling process. An instance is seen in fig. 1 j. Hence in 



