of Steel, Nickel] Cobalt, and Nickel-Steels. 65 



(c) Longitudinal magnetization produced by twisting a 

 circularly magnetized wire. 

 The longitudinal magnetization produced by twisting a 

 circularly magnetized wire presents the same character as the 



C{amp 



transient current above described. The experiment is very 

 difficult on account of the heating of the wires. To avoid 

 the rise of temperature, the iron and the nickel wires were 

 covered with uruslii (Japan lac) which has the special property 

 of being a very good insulator while, at the same time, the 

 melting temperature is comparatively high. The wire thus 

 insulated was stretched in the axial line of a secondary coil, 

 whose diameter was .1*0 cm. and whose total number of turns 

 was 540, -and a current of cold water was kept flowing 

 about it to keep the temperature of the wire uniform. Thus 

 maintaining the electric current in the wire constant, it was 

 twisted and the induced current in the secondary circuit due 

 to the longitudinal magnetization thereby developed was 

 measured by the ballistic method. 



As will be seen from the curve (fig. 15, p. 66) , the longitudinal 

 magnetization developed by twisting a circularly magnetized 

 iron wire attains a maximum when the mean circular field is 

 about 10. It then decreases, but in spite of the constant stream 

 of water, the heating due to electric current prevented the 

 experiment from being pushed to the point where the direction 

 of the current is reversed. To judge from the course of tho 

 curve, the tendency is such that there is a reversal. In nickel 



Phil. Mag. S. 6. Vol. 4. No. 19. July 1902. F 



