506 Transactions. — Miscellaneous. 



3,000,000 per second, but whether the increase of impedance 

 is due chiefly to an increase of K or of L, or both, cannot be 

 definitely settled ; but from experiments of the great absorp- 

 tion of energy of iron cylinders it is most probable that the 

 increase of the impedance is due to an increase in E, and not 

 to an increase in L. 



A far more delicate arrangement for detecting differences 

 of resistance and inductance in circuits was used in further 

 experiments. A differentially -wound solenoid was used with 

 one coil in one branch and a similar coil in the other, such 

 that when the currents in each branch were alike in amount 

 and phase there was no effect on the " detector " placed in 

 the solenoid. If a metal core was introduced into either 

 solenoid the balance was greatly disturbed, and in this way 

 the results of previous experiments were confirmed. The 

 method offered a very convenient means of determining the 

 resistance of iron wires, and the values obtained were quite in 

 accordance with previous results. 



VIII. Circular Magnetization op Iron Wires. 



"While experimenting on the resistance of iron wires which 

 passed close to the magnetometer, it was observed that the 

 deflection of the magnetometer varied very considerably with 

 the direction of the discharge, and also with the number of 

 discharges. The reason was at first not clear, but subsequent 

 investigation showed that it was due to the magnetization of 

 a neighbouring part of the wire by the transient current that 

 passed through it. When the wire was quite straight no 

 effect was observed, but if a slight bend was made near the 

 magnetometer the deflection varied according to the direction 

 of the discharge. The effect was very marked both in soft- 

 iron and steel wires, and shows what heavy momentary 

 currents must be circulating in the wires, for a steady current 

 of 10 amperes did not affect the deflection appreciably. The 

 effect of discharges through a short wire magnetized longitudi- 

 nally was then investigated. The discharge always reduced 

 the magnetization, whether the wire was of soft iron or steel. 

 This apparent demagnetization of the iron was due to the 

 surface -skin being "circularly' magnetized by the longi- 

 tudinal current through the wire. The heavier the transient 

 current the greater was the fall of magnetization. 



The following are examples of a few of the experiments on 

 the fall of deflection when the frequency of discharge was 

 3,000,000 and the value of the maximum current about 100 

 amperes : — 



(1.) Thin soft-iron wire, 0-01in. in diameter : Completely 

 demagnetized. 



