366 



DR. J. A. BARKER ON TBE HIGH-TEMPERATURE STANDARDS 



STEAM-POINT; 3. April 16, 1903. 



Observer, J. A. H. 



XXI. Accuracy of Gas Thermometer Constant Determinations. 



As an example of the kind of accuracy attained in the determination of the 

 constants of the gas thermometer, the individual values of the zero- and steam-points 

 taken before the comparisons in Series TI. is given along with the readings taken in 

 one complete determination of each. 



For calculation of experiments of this kind, where no gradual systematic drift is 

 expected, instead of utilising for calculating the individual values of the a. the single 

 determinations of the ice-point, the mean of the ice-points is taken for this purpose. 



The difference between the value of a. found before and after the comparisons is 

 within the limits' of experimental error. It will be seen from the table appended, 

 which gives in an abridged form the calculation of the gas thermometer temperatures 

 in the 13 experiments of Series II., that the difference has, however, been treated as 

 real, and assumed to vary with the time. A more serious change has, however, taken 



