26o THE ORIGIN OF LIFE 



do not last long enough to enable the absorption 

 which takes place during these intervals to be 

 appreciable. The collisions, therefore, in the 

 present instance probably last for a considerable 

 time, so long that during these intervals the 

 molecules in collision may be regarded as distinct 

 but unstable molecular groups or aggregates, which, 

 as we have endeavoured to show, ought to occur in 

 fluorescent and other luminous bodies. 



There can therefore be little doubt, from these 

 results also, that the formation of unstable groups 

 is one of the conditions of luminosity. 



From consideration as to the specific inductive 

 capacity of gases, it can be deduced from a 

 formula of Lorenz ^ that in a luminous gas the 

 spectral lines are not given out by every molecule, but 

 only by a comparatively small number of molecules, 

 and that the systems which give out one line 

 may be different from those which give out the 

 others. 



These points are in strict agreement with our 

 views on the subject which were arrived at in- 

 dependently in other ways, chiefly from consider- 

 ations bearing upon the phenomena of the change 

 of absorption during fluorescence, which involve 

 the temporary formation of new molecular aggrega- 

 tions to which the new emission and absorption 

 spectra of fluorescent substances are due.^ The 



1 J. J. Thomson, Archives Nierlandaises, 1902. 



2 British Association, Bradford, 1900, and Belfast, 1902. 

 Phil. Mag., 1901. 



