

The Electrical Resistance of Metals and Alloys, 271 



not been able to get over, and one which greatly decreases 

 the actual output of the machine, is caused by the warping of 

 the ebonite disks, which, although | inch thick, will not stand 

 true after being turned up, but move just sufficiently to throw 

 them out of balance and prevent their being driven at any- 

 thing approaching a high speed. The ebonite, moreover, is 

 not a sufficiently good insulator, and not only prevents my 

 getting a long spark but also reduces the possible efficiency 

 of the machine by becoming an increasingly good conductor 

 as the potential rises. 



XXYI. TJie Electrical Resistance of Metals and Alloys at Tem- 

 peratures approaching the Absolute Zero. By James Dewak, 

 LL.D., F.R.S., Professor of Chemistry in the Royal Insti- 

 tution, S)-c, and J. A. Fleming, M.A., D.Sc, F.R.S., Pro- 

 fessor of Electrical Engineering in University College, 

 London, fyc* 



[Plate II.] 



§ 1. FN the autumn of last year we published a short 

 A account f of experiments made by us during the 

 previous summer on the electrical resistance of metals, non- 

 metals, and alloys taken at the temperatures produced by the 

 evaporation of liquid oxygen when boiling under normal or 

 under reduced pressures. These experiments, which were 

 merely preliminary, revealed, however, the nature of the 

 difficulties to be overcome in repeating and following out this 

 work. During the past year a much more extended series of 

 investigations have been carried out by us on the same sub- 

 ject, but with more complete appliances for the production of 

 the large quantities of the liquid gases necessary as refrigera- 

 ting agents, and with greater care in the preparation of the 

 metallic wires used and in the physical measurements to be 

 made. 



This inquiry is still far from complete ; but the results are 

 of considerable interest as far as they have gone, and we con- 

 sider it may be desirable to place on record a portion of the 

 conclusions at which we have arrived. The general object of 

 this research may be stated to be the determination of the 

 Specific Electrical Resistance of Metals and Alloys between 

 the limits of temperature of about 200° C. and the lowest 

 obtainable temperatures approaching the absolute zero. We 

 particularly desired to investigate the variation of resistance 



* Communicated by the Authors. 



t Philosophical Magazine, October 1892, p. 327. 



