PEIRCE. — ANOMALOUS MAGNETIZATION OF IRON AND STEEL. 



663 



specimens were made 12 centimeters long so that our observations 

 might be more easily comparable with some which von Waltenhofen 

 and Fromme made. 



We have seen that if in a combination of a shell and a core the 

 exciting current be gradually reduced to zero, the residual magnetiza- 



FiGURE 17. The forma of some of the test pieces. 



tion of the shell is usually normal and that of the core reversed. If, 

 however, the current is suddenly broken, the magnetization of the 

 shell is often reversed and that of the core is normal. These facts may 

 be proved by removing the specimen from the solenoid and testing the 

 two pieces which then seem to be strongly magnetized, separately with 

 a compass or magnetometer. The separation of the members of the 

 system alters the polarization in each, however, and the process is not 

 to be recommended in accurate work. 



It is very difficult to study the residual magnetism in a very short, 

 stout soft iron cylinder, whether this be normal or anomalous, by the 

 use of iron filings, for since so many lines of polarization are closed 

 within the metal, the external action of the magnetization is usually 

 small. In the case of a combination of a shell and a core, where the 

 gap prevents the arrangements of polarization from being what they 

 would be in a solid cylinder of the same dimensions, it is often practi- 



