Dr. E. Bouty on the Magnetization of Steel by Currents. 193 



X 



2 



them to the action of the same magnetizing force ; let ~ be 



the distance from one pole to the near extremity in any needle ; 

 m, m' } m", ... the observed moments; we shall have 



VI 



l-X~l'-X 



(1) 



These equations permit us to verify that X is constant, and to 

 obtain its approximate value. It is found that X does not 

 vary, whatever may be the intensity of the magnetizing force. 



For needles of 0*920 millim. diameter -^ =10*33 millims. 



has been found; and in the same needles tempered hard, 



X 



_ =4*6 millims. Therefore the quantity X is connected with 



a 



the state of the steel ; it depends on its magnetic conductivity, 

 as will be seen in the course of this memoir. 



The Temporary-Magnetism Function. — The polar distance 

 being known, the curve which represents this function can be 

 constructed, just as in the case of hardened needles. The fol- 

 lowing Table was obtained for needles of 0*526 millim. dia- 

 meter. The second column refers to the temporary magnetism, 

 the third to the permanent ; the last gives the value of the 

 ratio r of these two quantities. 



Current. 



T. 



P. 



r. 



3-87 



1-003 



0-300 



3-343 



5-44 



1-589 



0-871 



1-867 



6-57 



2-416 







8-00 



3-375 



2-297 



1-891 



9-87 



3-702 







1156 



4-434 







14-84 



5017 



3-073 



1-633 



2025 



5487 



3-265 



1-681 



32-50 



6-704 



3-731 



1-796 



4375 



6449 







6037 



7543 



3-819 



1-975 



The preceding Table gives occasion for numerous remarks. 

 In the first place, we observe that the magnetization, whether 

 temporary or permanent, begins to be sensible at very low 

 values of the magnetizing force, which did not take place in 

 the case of the very hard-tempered steel ; the point of inflec- 

 tion of each curve is also nearer the origin ; and beyond it 

 the curves, especially those which relate to the temporary 

 magnetism, approach their asymptote much more slowly. In 

 a word, the variation of the quantities of magnetism takes 



Phil. Mag. S. 5. Vol. 3. No. 17. March 1877. O 



