250 



J. A. POLLOCK. 



values of the thermal conductivities and viscosities given 

 by him, a relation appears to exist between the two factors 

 which can be expressed by an equation of the form 

 f _ a (y-1) 



where a and n are constants. The precise arithmetical 

 adjustment of these constants may well await further 

 measures; in the meantime, with numerical simplicity as 

 well as physical accuracy in view, the equation may be 

 written ^ 7*32 (y-1) 



f 



,1-3 



If, in the original expression, n, the power of y, is put 

 equal to unity, the equation, with an appropriate value of 

 the constant, quite well represents the experimental results 

 with the exception of those for the monatomic gases. This 

 leads, in the case of perfect gases, to the simple relation 



^^-° = constant, 



where m is the molecular mass. 



In the following table, with the zero temperature 

 measures of k and ^, taken from Eucken's paper, I give, for 

 the calculation of f , the experimental results for c p and y 

 instead of the values of c v . The figures given for f in column 

 2 of Table II, deduced from the equation k = fvc v /y, are 

 thus wholly dependent on the results of experiment. 



Table I. 



1 



2 



3 



4 



5 



6 



Molecule. 



ra 



& o xl0 6 



^ o xl0 6 



c v 



y 



He 



4 



336 



187-6 



1-260* 



1-63 



A 



40 



390 



210-2 



0-123 



1-667 



H, 



2 



397 



85 



3-422f 



l-402f 



N 2 



28 



56-6 



167-6 



0-2429f 



l-412f 



o 2 



32 



57-0 



192-2 



0-2173f 



l-402f 



Air 



29 



56-6 



171 



0-2376f 



1-4051 



01, 



71 



18-29 



123-7 



0-115 



1-3231 



CO 



28 



54-25 



167-2 



0-2502* 



1-401 



NO 



30 



555 



179-4 



0-232 



1-394 



