570 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Peuckert, Zielinski and others who have written upon the subject, while 

 G. Wiedemann thought that his researches and those of Righi showed 

 that eddy currents in the iron, and alternating currents induced in 

 the exciting coil accounted best for the observed facts. In describing 

 experiments upon this so-called anomalous magnetization, Wiedemann 

 distinguishes between the permanent moment (P), that is, the remanent 

 moment after the current has ceased, and the total moment (7^), which 



Figure 31. The short coils of the magnet TP are in series with one 

 another and with a battery and an oscillograph. The current follows the Une 

 OCP or OESV according as the long coil of the magnet is open or closed on 

 itself. WTien at the point E the long coil which has been closed is suddenly 

 opened, the oscillogram is of the form ENQ which on account of the disturb- 

 ing effects of eddy currents is not like the upper part of the curve OCSP. 



is the moment when the current is steady at its highest value. This 

 last quantity is regarded as the sum of the permanent moment and a 

 moment ( V) which vanishes with the current. The suffix a attached 

 to P or T denotes that this moment has been reached after a gradual 

 change in the current, while the suffix / denotes that the current has 

 been suddenly opened or closed. According to Wiedemann, Ta is 

 always smaller than 7}, and Pf than Pg, but these differences are much 

 larger for short stout rods than for relatively long ones, where they 

 become insignificant. (Pa — Pf)/Pa is smaller in the case of a rod 

 made of a bundle of insulated soft iron wires than in the case of a solid 

 rod of the same dimensions. As C is made larger, Tf—Ta attains a 

 maximum and then sometimes decreases slightly. If the rod to be 

 magnetized is surrounded by a thick metal tube in which eddy currents 

 can be induced, Pf is slightly increased, especially if the current be 

 first slowly raised to C and then suddenly stopped. If shorter and 



