PEIRCE. — ANOMALOUS MAGNETIZATION OF IRON AND STEEL. 653 



upon what happens in a core magnetized in lines which are often closed 

 within the metal, after the magnetizing current has been removed and 

 the changes which come from the rapidly changing demagnetizing forces 

 from the ends of the core itself are going on. We may content ourselves 

 at present, therefore, by showing that, so far as we know, oscillations 

 are always present in the circuit of the exciting current when anomalous 

 magnetization is afterwards to be detected in the core. We must not 

 close our eyes, however, to the fact that the demagnetizing forces due 

 to the magnetic distribution itself complicate the problem. 



Residual Magnetization in Bundles of Fine Iron Wire. 



The remanent magnetism in a bundle of fine iron wire so shellacked 

 as to prevent electric flow from one wire to the next, should be inter- 

 esting because the effects of eddy currents in the core itself are nearly 

 avoided. Fromme's work in this direction seems not to have been con- 

 clusive, and it will be instructive to consider two or three experiments. 



Two similar solenoids were placed horizontal with their common axis 

 perpendicular to the meridian, and with their nearer ends about 15 

 centimeters apart. These solenoids were so connected in series that a 

 current sent through the circuit did not affect the needle of a magneto- 

 meter between them. A bundle of fine, varnished iron wire forming a 

 cylinder 12 centimeters long and 3 centimeters in diameter was then 

 introduced into one of the solenoids and tested to make sure that it 

 had been properly demagnetized. A small current was next sent 

 through the circuit and the wire put several times through the cycle 

 corresponding to this current. Then the circuit was suddenly broken 

 so as to bring the current from its full value to zero and the needle 

 deflection caused by the residual magnetism was observed. This pro- 

 cess was then repeated for a series of currents of increasing strengths. 

 The results of the work are given in Table III. H represents the 

 strength which the current would cause in the solenoid if the disturb- 

 ing effects of the iron itself were not present. D shows the deflections 

 of the needle on its scale caused by the residual moments. It is evident 

 that there was nothing here similar to the abnormal magnetization of a 

 soft iron solid cylinder of the same dimensions under similar conditions. 



