118 DIKECT PROPERTIES OF MOLECULES 331 



had to do with magnitudes which are capable of direct 

 measurement. But since these magnitudes are much 

 smaller than the smallest that is microscopically visible, 

 and since a knowledge of them is attainable only in 

 roundabout ways by the use of many kinds of measures 

 and uncertain conclusions, we must rejoice and, at least 

 provisionally, be content that we have found values which 

 differ only so little from each other that they, in all cases, 

 are of the same order of magnitude. 



We shall be able to form a judgment with greater 

 certainty as to the trustworthiness of these figures when we 

 shall have compared them with the values deduced from 

 different speculations ( 122). But we may now attempt 

 to decide the question, which method of determining the 

 absolute magnitude of the molecules deserves preference 

 over the other. The answer can scarcely be doubtful if 

 we remember that the determination by means of the 

 mechanical measurements cannot give too small, but only 

 too large values of the molecular diameter. The smaller 

 of the values found is therefore to be looked upon as the 

 more credible, and I therefore use the value 

 s- = O2 x 10~ 7 cm. 



in some further conclusions as to the state of gaseous 

 molecules. 



But there is still a further reason which we may give 

 for preferring the values calculated from the dielectric 

 capacities and the refractive indices. The equality of the 

 path- volume ( 69), which the former values failed to give 

 ( 116), comes into view when the latter are employed in the 

 calculation, as is proved with sufficient accuracy by the 

 following values of the product s\/L calculated by Dor n : 



Air 1-55 



Carbonic acid . . . .1*42 



Hydrogen . . . . 1'84 



Carbon monoxide . . . 1'86 



Nitrous oxide . . . . 1*50 



Ethylene .... 1'56 



Marsh gas .... 2'12 



