358 Dr. T. Ewan and Mr. Haldane Gee on 



readings of air thermometer and the platinum thermometer 

 with even greater accuracy than Callendar had supposed. 



Under these circumstances we thought it desirable to 

 elaborate a method which would allow of the platinum 

 thermometer being standardized and then used for com- 

 parison with mercury thermometers, and especially to find 

 what degree of accuracy could be attained without the use 

 of elaborate precautions or special apparatus. 



To determine the fixed points on the scale of the plati- 

 num thermometer we immersed it in the vapour of water 

 boiling under diminished pressure. The same apparatus 

 served for the comparison with the mercury thermometer. 

 Regnault's tables of the pressures of aqueous vapour 



