PEIRCE. 



RESISTIVITY OF HARDENED CAST IRON. 



199 



••• 



shown by Figure 4. After this rod had been demagnetized as well as 

 possible in a solenoid by the use of a series of currents alternating in 

 direction and gradually decreasing in intensity, and then had been 

 magnetized again to satu- 

 ration in a solenoid as • * *C * * • 

 before, Diagram A came • * * 

 back again. ^ • , 



Another unequally , 



hardened steel rod of the , K 



same kind gave the filing 

 diagram shown in Figure 

 C, and in this case the 

 distribution of magnetism 

 was that indicated in 

 Figure 5. 



Figure 6 shows in the 

 curve HYU, of which the 

 horizontal line through E 

 is the base, the resistivity 

 of a rod of cast iron of 

 the dimensions of the 

 specimens used in this 

 investigation. For this 

 particular piece the resis- 

 tivity at one end corre- 

 sponded to the annealed 

 state and at the other 

 end to glass-hardness. 

 After this rod had been 

 magnetized in a solenoid, 

 the distribution of mag- 

 netism in it was that 

 represented by the dotted 

 curve GZX. This rod 

 when magnetized irregu- 

 larly on the motor gave A B 

 the diagram LCK, but Figure 6. 

 when the rod was demag- 

 netized and again magnetized in the solenoid, the distribution GZX 

 returned. It is interesting to notice that in the cases shown in 

 Figures 4 and 6, the motor gave a smooth distribution of B while the 

 solenoid gave an irregular one. When real consequent poles are pres- 



-E 



