220 PHENOMENA DEPENDENT ON MOLECULAR PATHS 85 



which expresses the value of rj at the temperature = $ + a~ l 

 in terms of rj Q which corresponds to the freezing-point. 



With this formula Sutherland first succeeded in very 

 exactly reproducing the law of the observations which 

 Ho 1m an had made on the viscosity of atmospheric air at 

 different temperatures. Putting C = 113, he calculated the 

 following values of the ratio r)/7j Q which are put opposite 

 the corresponding observed values : 1 



Atmospheric Air. 



With the same value of C he was able to represent right 

 satisfactorily the ratios observed by Bar us. 2 



Atmospheric Air. 



There is a still better agreement between the formula 

 and Holman's 3 observations on the viscosity of carbonic 

 acid, if for this gas the larger value C = 277 is put. 



1 Proc. Amer. Acad. 1885, xxi. p. 13. 



2 Amer. Journ. of Sci. 1888 [3] xxxv. p. 408. 



3 Proc. Amer. Acad. 1885, xxi. p. 16. 



