12 ART. 9. H. NAGAOKA, AND S. KUSAKABE : EFFECT OF 



increase between 630° and 620.° The increase, however, goes on 

 slowly when the metal is cooled below 600°, and the curve dis- 

 plays singular trends, at temperatures nearly coinciding with 

 those above mentioned. The magnetization below 380° becomes 

 greater than that on the heating course, so that on reaching 

 ordinary temperature, the difference between the final and initial 

 intensities of magnetization amounts to one-third of the total 

 intensity. In experiments in stronger fields (.sy=^118) the same 

 characteristics are shared by the heating and cooling curves as 

 shown in Fig. 10, PI. II. The corrugations are made more cons- 

 picuous and lie at somewhat higher temperatures. 



Nickel. The critical temperature of this metal lies far below 

 that of iron and cobalt, and the heating and cooling curves 

 assume smooth courses. The specimen tested was of nearly pure 

 nickel; the critical temperature for §' = 39 being about T)00°; it 

 rose to 580° for §' = 177, showing that the said temperature in- 

 creases Avith the field strength. On cooling, we notice that the 

 magnetization begins to recover at temperatures about 100° lower 

 than that at which it vanishes on heating, just as in iron and 

 steel. The difference in the magnetization after cooling down to 

 ordinary temperature is tolerably large in moderate fields, but 

 becomes smaller as the field strength is increased. An inspection 

 of the curve in Fig. 11, PI. II. will make these points clear. 



Cobalt. The general character of the curve of magnetization 

 plotted against temperature is the same as for other ferromagnetic 

 bodies, but as already noticed, the variation in the magnetization 

 of the metal surpasses all other sul stances thus far examined. 

 This remarkable difference can be easily traced in the curves, of 

 which three are given in Fig. 12, PI. II. e.g. fè'=39.3, 97.1, 

 and 186.7. 



