634 



CONSTANTS OF MAGNETISATION. 



These results, calculated by M. Stoletow,* lead to values for 

 the coefficient of magnetisation which first increase and attain a 

 maximum of no or 120, corresponding to magnetising forces of 

 4 to 5 units. 



Stoletow himself used a ring of rectangular section ; he found 

 values increasing from 21-5 to 174*2; the maximum takes place 

 for a field equal to 3*21. The curve I (Fig. 245) represents the 



150 



100 



50 



10 



Fig. 245. 



coefficient k as a function of the field according to Stoletow ; the 

 curves II and III refer to the experiments of Quintus Icilius. 



Professor Rowland! has investigated, by the same method, 

 several kinds of iron and steel in the form of rings with a cir- 

 cular section. Curves I, II, III (Fig. 246) represent the total 

 magnetisation, the temporary magnetisation, and the permanent 

 magnetisation for good Norwegian iron. They show that the 

 increase of magnetisation is at first very rapid for small forces ; 

 that the magnetisation is at first simply temporary (and this effect 

 is still more marked for steel than for iron) ; lastly, that the maxi- 

 mum is attained more rapidly for the permanent than for the 

 total magnetisation. 



1205. Instead of representing the intensity of magnetisation, 

 or the coefficient , as a function of the magnetising force, Row- 

 land uses a mode of representation which seems far preferable ; 



* STOLETOW. Pogg. Ann., Vol. CXLVI., p. 442. 1872. 

 t ROWLAND. Phil. Mag. [4], Vol. XLVI., p. 140. 1878. 



