124 H. Nagaoka on Transient Electric Current produced 



the investigation of the effect of twist in the magnetization of 

 nickel and iron, I tried some preliminary experiments on the 

 transient current produced by twisting magnetized wires. 

 Thereby I hoped to trace some connexion between the transient 

 current thus observed and the reversal of polarity* produced 

 by twisting magnetized nickel wire, which is at the same 

 time subjected to longitudinal stress. Though nothing striking 

 was obtained in this direction, results not hitherto made known 

 by the researches of Matteucci f and Ewing \ were obtained. 

 The following is the description of the experiments made in 

 July and September, 1888. 



The wire to be examined was well annealed and hung in a 

 magnetizing solenoid, The coil was 30 centim. long and 

 wound in 12 layers of thick copper wire, giving a magne- 

 tizing field of 36*7 units for a current of one ampere. The 

 upper end of the wire was held fixed, while the lower was 

 attached to a twisting apparatus provided with a graduated 

 circle and a pointer. The two extremities of the wire were 

 electrically connected to a low-resistance ballistic mirror- 

 galvanometer. The transient current was measured by the 

 first swing of the galvanometer. The deflexion was read 

 after suddenly twisting the wire between two extreme limits 

 of twist. Generally, it was after a number of twistings in 

 both ways from the initial position of no twist, that the 

 transient current settled to its final value. 



Since the present investigation was undertaken with a 

 view to ascertain the relation, if such exists, between this 

 transient current and the reversal of polarity, the effect of 

 longitudinal stress on the transient current was also looked 

 into, as this played an important part in producing the re- 

 versal mentioned. 



A nickel wire 30 centim. long and 0'5 millim. in radius 

 was treated in the way above mentioned, the angle of twist 

 amounting to 60° in both directions from the initial position 

 of no twasting. The first experiment was performed under 

 no longitudinal stress ; the transient current produced by 

 suddenly twisting the wire in various magnetizing fields was 

 measured, the field being gradually increased from to 110 



* See " Effects of Torsion and Longitudinal Stress on the Magnetiza- 

 tion of Nickel," Journ. of the Coll. of Science, Imp. Univ., Japan, 

 vol. ii., or Phil. Mag. Feb. 1889 ; and also " Effect of Twist on the Mag- 

 netization of Iron and Nickel/' Journ. of the Coll. of Science, vol. iii. 

 At the end of the latter paper a short sketch of the results on the transient 

 current is given. 



t See "Wiedemann's Electricit'dt, Bd. iii. § 771. 



% Proc. Roy. Soc. vol. xxxvi. 1884. 



