MOLECULAR AGGREGATION 261 



hypothesis we put forward in this book that 

 luminosity is thus merely the high frequency 

 radiation resulting from a catalytic process is 

 thus greatly strengthened by its bearing the 

 formation of large groups, even consisting of chains 

 of molecules which should by no means be broken 

 up as quickly as might at first be imagined, 

 when chemical interactions take place within the 

 groups themselves, and the linkage in such cases 

 would thus be sufficiently great to enable them to 

 hold together for a considerable time, the radiation 

 also being sufficient by its presence to mitigate 

 very greatly the effects of molecular collisions. 

 For it may be inferred from Professor Poynting's 

 results^ that spheres of molecular dimensions, by 

 radiating intensely, can so exert a repulsion on 

 each other so as to prevent themselves from doing 

 much damage by mutual collisions. 



These systems, however, may exist even when 

 such molecules are not actively radiating : but the 

 duration of their existence would doubtless be much 

 shorter. Such encounters as may last so long 

 that the colliding molecules can be looked upon as 

 systems differing from the separate or isolated mole- 

 cules are no obstacles in the way of the dynamical 

 theory of gases, although they are extremely few 

 and far between. They may be regarded as the 

 chosen few amongst the masses. 



It will be remembered that the results of Clerk 



1 " Eadiation in the Solar System," Philosophical Transac- 

 tions, 1903. 



