80 Resistivity of Mercury at the temperature of Liquid Air. 



FIG. l. 



Temperature in Platinum Degrees. 



S3'14 C.G.S. units per degree rise of temperature on the platinum 

 scale ; between 108'4 and 57'6 the mean increase in resistivity in 

 C.Gr.S. units per degree is 109*6 ; in the liquid condition between the 

 temperature 35'2 and the mean increase in resistivity in C.Gr.S. 

 units per degree is 83*2; temperature measurement being on the 

 platinum scale as above denned. It may be stated here that tem- 

 peratures defined by this platinum scale do not differ by more than 

 about 0'5 from the Centigrade scale down to temperatures of 100, 

 but that the temperature of boiling liquid oxygen which, on the 

 Centigrade scale is denoted by 182, is, on the platinum scale 



