208 



i .'. .-iiiil K. 'I'. .' 



" On the Change of Resistance in Iron produced by Magnetisation." 

 I'y ANDREW GRAY, LL.D., F.R.S., Professor of Natural Philo- 

 sophy in the University of Glasgow, and EDWARD TAYI.OI; 

 JONES, D.Sc., Professor of Physics in the University College 

 of North Wales. Received May 30, Read June 21, 1900. 



The experiments described below were made with the object of 

 determining simultaneous values in a specimen of soft iron wire of the 

 magnetising force, the magnetisation, and the change of resistance due 

 to magnetisation. In all the measurements hitherto made of magnetic- 

 changes of resistance no attempt seems to have been made to deter- 

 mine at the same time the magnetisation ; in fact, the results which 

 have been obtained for bismuth might appear to indicate that there is 

 but little, if any, connection between magnetisation and change of 

 resistance. The results herein described, on the other hand, indicate 

 that there is a somewhat close connection between the two phenomena, 

 and make it clear that further measurements on similar lines would 

 have some value. 



Mo'.<nrcment of Resistance. 



Preliminary trials showed that great difficulty would be experienced 

 in determining the magnetic change of resistance in iron unless great 

 precautions were taken to eliminate the effects of rise of temperature 

 in the wires due to the passage of even feeble currents. In the 

 arrangement finally adopted, two coils of soft iron wire P, Q (fig. 1) 



FIG. 1. 



L 



M 



