PEIRCE. — ANOMALOUS MAGNETIZATION OF IRON AND STEEL. 647 



suddenly destroyed. OMNL shows the remanent magnetism after 

 currents which have caused negative moments. The first curve indi- 

 cates that the residual magnetism was reversed in sign, but this was 

 never the case after negative currents. In Figure 8 similar curves are 

 shown for the shorter specimen and it appears that some of the nega- 



Figure 8. Magnetic bias in a rod of cold-rolled shafting which the de- 

 magnetizing process used could not remove. 



tive currents left anomalous residuals. Annealing removed the bias 

 from the first piece almost completely. 



Apart from details the observations recorded in this section are in 

 general agreement with much that has been written upon this subject 

 as given ^ in Wiedemann's EleMricitdt. Wiedemann denotes by T the 

 total magnetic moment of a bar when exposed to the action of a mag- 

 netizing field and by P the residual moment after the field has disap- 

 peared. He uses the suffixes a and / to denote that the moment of 

 which he is speaking has been reached by a gradual change in the 

 exciting field or by a very sudden one. He says that Tf is always 

 larger than Ta and Pa than Pf, algebraically considered, but these 

 differences are only large in short rods. Pf is slightly increased if the 

 rod to be magnetized is surrounded by a thick tube of nonmagnetic 

 metal. {Pa — Pf) /Pa is smaller for bundles of insulated soft iron wire 

 than for solid rods of the same dimensions. Inversion comes with 

 longer rods when the exciting field is weak than when it is strong. 

 Some of these statements will need to be discussed in the light of ex- 

 periments upon divided cores. The statement copied by Wiedemann 



* Bd. iv, §§ 338-340. 



