40 Dr. C. Chree. Investigations on 



37. A similar treatment of the entire number of observations with 

 these four thermometers viz., twenty-four with K 3 , twelve with K 7 , 

 ami twenty-one with both KI and KI making use of the individual 

 fundamental intervals only, gave the following results : 



Table XIII. 



As we shall see later, the thermometer KI has undergone a change. 

 Its pt s has risen, and the apparent smallness in the variation in its case 

 in Table XIII seems largely due to the fact that amongst the latest 

 experiments there was a preponderance of cases where the barometer 

 was below 760 mm. 



38. Tables XII and XIII prove, I think, beyond a doubt that the 

 Callendar-Griffiths reduction formula (10) assigns an appreciably too 

 small value to the variation of the temperature of sulphur vapour with 

 pressure near 760 mm. This is the conclusion to which the results 

 from every single thermometer point, and the phenomena are too con- 

 spicuous to be attributed to accident or to experimental errors. 



The agreement between the results in Tables XII and XIII is, I 

 admit, not all that might be desired, and any numerical conclusions 

 based on them are perhaps hardly likely to be final. Still I have 

 thought it worth while to see what these conclusions are, proceeding as 

 follows: 



Suppose that the Callendar-Griffiths formula (10) is defective in 

 omitting a term in (p - 760) 2 and in assigning an incorrect value to the 

 constant multiplier of the term in /> - 760. 



Then, supposing as before 8 = 1-5, we should replace (13) by 



pt =^+(0-0723 + x) (p- 760) + /(/> -760) 2 (14), 



where x and y must be determined from the experiments. As all the 

 observations had been already worked up applying (10), it seemed 

 simplest to take for data the values calculated in this way for ptg, 

 determining x and // by least squares from the observed differences 

 between the calculated values and their mean. 



