PEIRCE. — CHANGES IN INDUCTANCES OF ELECTRIC CIRCUITS. 569 



short steps. If, after the current has remained steady for a short time 

 at the strength C it be made to decrease to zero, the residual moment 

 of the bar will be less if the circuit be suddenly opened than if the 

 decrease be made slowly by introducing more and more resistance."* 

 If the soft iron bar to be magnetized was stout and relatively short, 

 von Waltenhofen was sometimes able to reverse the direction of the 

 remanent magnetism by a sudden break of the circuit. In one instance 

 where the length of the bar was about ten centimeters and the diam- 



FiGURE 30. The short coils of the magnet TP are in series with one an- 

 other and with a battery and an oscillograph. The current follows the line 

 OPR or the Une OLM according as the long coil of the magnet is open or 

 closed. When at the point P, the long coil circuit is suddenly closed, the cur- 

 rent in the battery follows the line PSN, which despite eddy currents is not 

 very unhke the upper part of OLM. 



eter about two centimeters, the magnetic moment while the current 

 was passing was about 45 units, and about —0.20 when the current 

 had been stopped. It seemed to von Waltenhofen that these phenom- 

 ena could not be due to the induced currents caused by the sudden 

 changes in the exciting current, and he explained them as consequences 

 of the inertia of the molecular magnets turning in a viscous medium. 

 This view seems to have been taken by Fromme, Auerbach, Ewing, 



* Von Waltenhofen, Poggendorff's Ann. 120, 1863; Fromme, Poggen- 

 dorff's Ann., Ergbnd. 7, 1876; Wied. Ann. 4, 1878, 5, 1878, 13, 1881, 18, 1883, 

 44, 1891; Bartoli and Alessandri, Nuovo Cimento, 8, 1880; Righi, Mem. 

 di Bologna, 1, 1880; Peuckert, Wied. Ann. 32, 1887; Auerbach, Wied. Ann. 

 14, 1881, 16, 1882; Winkelmann's Handbuch der Physik, Band 5; Wiede- 

 mann, Lehre von der Elektricitat, Band IV; Ewing, Magnetic Induction, §84; 

 Gumlich und Schmidt, Electrotechnische Zeitschrift, 21, 1905. 



