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



feront diameters ; nor is there for those needles a real function 

 of temporary magnetism ; and we have just seen that, between 

 certain limits of thickness, the ratio of the two quantities of 

 magnetism depends on the diameter — a result perfectly incom- 

 patible with the existence of these two functions. Yet if, 

 tempering a series of needles of the same diameter, we after- 

 wards reduce them to different diameters by the action of an 

 acid, we know already that there is a well-determined function 

 of permanent magnetism ; and there is also a function of tem- 

 porary magnetism: the ratio r becomes independent of the 

 diameter ; it retains for all the needles the value corresponding 

 to the diameter of the mother needles according to formula (3). 

 The following Table refers to needles of initial diameter equal 

 to 1-178 millim.:— 



Current. 



1 



Difference. 



Mean yalue. 



Calculation. 



19-55 

 27-91 



'3625 

 45-50 



2323 

 1-862 

 1 -609 

 1-498 



2 449 

 1-786 

 1-556 

 1 442 



-01 26 



+ 0076 

 +0053 

 +0-056 



The second column gives the mean of the values of r ob- 

 tained with superficially corroded needles reduced to 1*088, 

 0-348, 0-854, and 0-762 millim. 



We can also assure ourselves directly that the function of 

 temporary magnetism is constant, as we have that the function 

 of permanent magnetism is so. The curve T (fig. 3) was ob- 



Fig. 3. 



