8 



Professor Deivar 



[Jan. 20, 



conjunction with my friend, Professor J. A. Fleming, D.Sc, F.E.S. 

 The experiments are made by means of a resistance coil shown in 

 Fig. 5, consisting of a piece of notched mica coiled with the fine 

 wire to be tested, and of stout insulated copper-rod connections. 

 The coil and connection are immersed in liquid oxygen contained 

 in a vacuum test-tube, and the temperature of —200° C. can be 

 reached by exhausting the oxygen by means of a powerful air- 

 pump. The results point to the conclusion that absolutely pure 



Fig. 6. 



ZO 



+ TEMPERATURE — 



Electrical Resistance of Metals at Low Temperature. 



metals seem to have no resistance near the zero of temperature as 

 indicated by the above curves (Fig. 6) obtained by experiment. 

 With alloys there is little change in resistance, as indicated in 

 the curves (Fig. 7). The conductivity of carbon decreases with 

 low temperatures, and increases with high ones. At the tempera- 

 ture of the electric arc, carbon appears to have no resistance. 



The optical constants of liquid oxygen, ethylene, and nitrous 

 oxide have been so far determined, and in this matter my colleague, 

 Professor Liveing, has been associated with me in the conduct of 

 this work. The results obtained are given in the following table, 



