Effect of a Magnetic Field on Metallic Resistance. 731 

 Conclusion. 



In conclusion I wish to acknowledge the assistance of 

 Mrs. Perkins in making the capacity adjustments and re- 

 cording the beat of the pendulum at which deflexions began 

 for actinium emanation, also to express my indebtedness to 

 Prof. Sir Ernest Rutherford for his continued interest in the 

 progress of the investigation, and to Mr. Marsden for many 

 helpful suggestions. 



LXXXIV. On the Effect of a Magnetic Field on Metallic 

 Resistance. By Walter A. Jenkins, M.Sc, 1851 Exhi- 

 bitioner, Research Student of Emmanuel College, Cambridge* . 



[Plate X.] 



THE following experiments were carried out in order to 

 obtain further evidence on the above effect. Nickel was 

 the metal used, as the author had previously carried out 

 experiments on the elongation of nickel under a longitudinal 

 magnetic field and, as will appear later, in all probability 

 there is some relation between the two effects. 



Apparatus. 



The nickel resistance consisted of a short piece of very fine 

 wire soldered at right angles to the ends of two thick 

 copper wires. The copper wires fitted tightly into rather 

 wide capillary tubing, attached rigidly to a block of wood. 

 This arrangement allowed of the placing of the resistance in 

 any desired position between the poles of the electromagnet. 



The nickel wire— supplied by Hartmann and Braun, 

 Frankfort — was about *5 cm. long and '0015 cm. diameter. 

 Its resistance at 18° 0. was 3'5173 ohms. 



An electromagnet was used for supplying the magnetic 

 field and, as the resistance was of very small dimensions, 

 fairly large fields could be employed. The cross-section of 

 the pole- pieces was large enough to ensure fairly uniform 

 fields round the resistance. The resistance was measured 

 by a Wheatsfcone bridge method — a compensating nickel 

 resistance and two manganin resistances in oil formed the 

 other three arms of the bridge. Deflexions of the galvano- 

 meter were noted instead of obtaining a balance every time 

 and, as the galvanometer was calibrated before and after 

 the experiments, this method proved quite satisfactory. 

 There was a slight creep of the spot of light owing to 



* Communicated by Sir J. J. Thomson, O.M., F.R.S. 



