302 



H. E. J. G. du Bois on Magnetization in 



without any magnetic observations having been made. In 

 fact these are quite out of question in the present case ; and 

 accordingly no absolute data have ever been given for mag- 

 netite or loadstone that I am aware of. 



III. Conclusion. 



§ 15. There can be no doubt that the curves of fig. 2, 

 especially those for cobalt and nickel, show a tendency to 

 a limiting value of magnetization. This of course can never 

 actually be observed, but the values of 3 can hardly exceed 

 1630, 1200, 530 C.G.S. respectively for the steel, cobalt, 

 and nickel used (at 100°). Though, as explained in § 12, iron 

 unfortunately happened to give the least trustworthy results, I 

 may infer from my observations that the value 1750 cannot 

 be far from the truth (also at 100°). As regards the im- 

 portant question whether the approach is an asymptotic one, 

 or whether 3 reaches a maximum with finite values of .0, 

 thence to rediminish *, I cannot pretend to decide it any 

 more than Messrs. Ewing and Low. The apparent slight 

 decrease in the case of nickel (see Table I. ; 3 = 525) is within 

 the range of experimental error. 



NP 



Accordingly the general type of the well-known suscepti- 

 bility curves fc = hmct. (3) has the point of inflexion I, as 

 was indeed first shown for iron by Fromme and Haubner 

 (see § 1, footnote). Its continuation beyond the final ex- 

 perimental point P is a matter of inference. If there be an 

 asymptotic limit to 3, the curve will cut the axis of abscissae 

 in a point Q, and the shape of the end P Q will depend on 

 the law of approach of 3 ; e.g. if the approach be like that 



* See Maxwell, Treatise, ii. § 844. It may be well to observe that even 

 in a field of 35,000 O.Gr.S. the magnetization of bismuth, the most 

 diamagnetic metal known, would reach but — '5, i. e. — y 1 ^ per cent, of 

 the limiting value for nickel, so that its superposition on the latter would 

 probably escape observation. 



