194 Dr. E. Bouty on t lie Magnetization of Steel by Currents. 



place with much less steepness, and the curves referring to it 

 present less analogy with simple broken lines, such as would 

 be given by the old theory of the coercive force. This cha- 

 racter also presents itself most distinctly in the curves given by 

 Rowland for various sorts of iron, contrary to the results fur- 

 nished by Bessemer steel. 



Let us also notice that the ratio r, which we have found de- 

 creasing towards a certain limit when the intensity of the 

 magnetizing force increased indefinitely, presents in the case 

 of soft-tempered steel a very definite minimum, beyond which r 

 augments very sensibly. Although this minimum presents 

 itself here for the first time in my experiments, its existence 

 appears to be pretty general ; I find it in all the experiments 

 made by Rowland upon iron, steel, nickel, and cobalt — although 

 with special characters, according to the state and the nature 

 of the substance * : — 



F. r. 



C 0-2673 3-875 



Norway iron, magnetic ... < 0*9305 1*350 minimum. 



( 36*86 2-099 



C 0-1456 3-823 



Burden's "best," normal... < 1*655 1*366 minimum. 



( 36*60 2*073 



( 0*553 2*193 



Burden's " best," burnt ... -I 1*317 1*243 minimum. 



( 51*03 1*511 



I 0-1356 18*176 



Bessemer steel, normal ...< 7*495 1*358 minimum. 



( 38*99 1*523 



C 1*084 12*47 



Stubb's steel wire < 20*54 1*519 minimum. 



( 38-64 1-692 



C 2-136 2*394 



Cast nickel, normal < 5 -900 1*472 minimum. 



( 82*92 2*227 



f 3*925 7*160 



Cast cobalt, normal < 21*06 2*452 minimum. 



(117*00 3*244 



The limits within which are comprised the magnetizing 

 forces employed by me are narrower than those attained by 

 the American savant; and it appears to me very probable 

 that the minimum of r would have been clearly marked, even 

 in the case of very hard-tempered steel, if the upper limit of F 



* The values of r have been calculated from the numbers given by 

 Rowland in the two papers published in the ' Philosophical Magazine,' 

 August 1873, and November 1874. 



