The Magnetic Properties of almost pure Iron. 36^ 



Table III. 



Date. 



Kesistance at atmospheric 

 temperature in ohms. 



1st November, 1897 



3rd „ „ .... 



13th „ „ 



20th „ „ .... 

 » » >»•••• 



4th January, 1898 



» 5> >J .... 



-4625 

 0-4590 

 -4592 

 0-4589 

 r 3 = -2269 

 r 4 = 0-2270 

 r 3 = -2275 

 r 4 = -2277 



The strip was mounted on November 1, 1897, and submitted to 

 currents varying from 100 amperes downwards. On November 20, 

 1897, it was adjusted for r 3 , r 4 . The results show that there is an 

 initial diminution of resistance, and that then the resistance remains 

 practically constant. This is worth noting, as this material is 

 largely used at the present time, on account of its low temperature 

 coefficient. The manganin strip is unvarnished and exposed to the 

 atmosphere of the engine room. The conditions are therefore not 

 the best to secure constancy of resistance, but in all probability the 

 initial diminution is due to the brazing. 



Messrs. C. J. Evans and H. H. Hodd have given me valuable 

 assistance, not only in the experimental part of this paper, but also 

 in the working out of the results. Messrs. Simpson, Greenbank, 

 and Davey, the present Student Demonstrators in the Siemens 

 Laboratory, have also helped me. I wish to acknowledge this, and 

 to tender my thanks to these gentlemen. 



" The Magnetic Properties of almost pure Iron." By Ernest 

 Wilson. Communicated by Dr. J. Hopkinson, F.R.S. 

 Received January 11, — Read January 27, 1898. 



One of the two rings of almost pure iron supplied by Colonel Dyer, 

 of the Elswick Works, to Sir Frederick Abel, K.C.B., F.R.S., by 

 whom they were sent to Dr. John Hopkinson, F.R.S., has already 

 formed the subject of a communication,* and is herein referred to as 

 Pure Iron I. As this pure iron has not been directly tested for dis- 

 sipation of energy due to magnetic hysteresis, and the second ring- 

 was available, the author thought it would be interesting to examine 



* « Eoy. Soc. Proc./ vol. 52, p. 228. 



