252 J. A. POLLOCK. 



In this second table, the values of f, derived from the 

 expression f = 7*32 (y - l)/y 13 , are entered in column 3. 

 An idea of the physical accuracy of the calculated results 

 may, therefore, be obtained from a comparisou of these 

 figures with those in column 2. There are certainly large 

 differences between the calculated and observed values for 

 some gases, but the experimental determinations cannot 

 be considered in all cases as final. 



The last column of Table II contains the values of 

 wiyJcJr} o . As prevously mentioned, with the present experi- 

 mental results, constancy of the value of the ratio is only 

 to be expected in the case of perfect gases with molecules 

 of an atomicity greater than 2. The approximate similarity 

 of the figures in some number of instances is, therefore, 

 perhaps more remarkable than the divergencies in the 

 other cases. 



It is interesting to note the rise that has taken place in 

 the values of the thermal conductivities. For many years 

 the determinations of f for diatomic gases were cited in 

 support of Meyer's well known theoretical deduction, f = 

 1*6027. Now, from Eucken's measures of the thermal con- 

 ductivities, the value of f for these gases is 1*9. 



