Dr. E. Bouty on the Magnetization of Steel by Currents. 127 



Initial diameter 1*178 rnillim. 



Current. 



Diameter. 



Mean. 



]mm.08S. 



Omm.948. 



ram -854. 



0mm. 762. 



19-55 

 2791 

 3625 

 45-50 



01800 

 0-3709 



0-6298 

 0-8697 



01722 

 03764 

 0-6424 



0-8863 



01202 

 03350 

 0-6078 

 0-9078 



0-3783 

 0-6821 

 0-8712 



01631 

 0-3663 

 0-6424 



0-8881 



To avoid the errors which might result from an inaccurate 



valuation of the diameter*, this Table contains, opposite to 



each value of the current-intensity, the fraction of the extreme 



quantity of magnetism attained by each group of needles. 



These numbers should be equal in one horizontal line, if there 



really exists a magnetizing-f unction. 



M 

 Here are, besides, the values of the quotients fju — ^ : — 





M 



D. 



D 2 ' 



millini. 



rnillim. 



1-088 



0-1346 



0-948 



0-1291 



0-854 



0-1095 



0-762 



0-1125 



Mean 0-1214 



The slight decrease in fju is to be attributed to the valuation 

 of the last two diameters being a little too high, as explained 

 in the note. 



The results relative to the magnetizing-function of tempered 

 steel have been confirmed by the study of bars of 7-10 mil- 

 lims. initial diameter. 



Distance of the Poles from the Extremities. — The following 

 Table gives the double distance of one pole from the nearest 

 extremity for needles of 0*553 rnillim. diameter: — 



* The corroded needles present microscopic holes, minute solutions of 

 continuity ; the estimation of their diameter, made with the spherometer, 

 is therefore a little too high. 



