330 THE ORIGIN OF LIFE 



been described as the result of careful quantitative 

 experiments, has led up to the theory of fluorescence 

 herein put forward. The question has been discussed 

 as to whether the change of absorption can be the 

 result of the increased amplitudes of the vibrations 

 of the fluorescent light, or whether it is due to the 

 formation of free periods — not previously existing in 

 the molecules which give rise to the absorption, but 

 brought about by the conditions which excite fluor- 

 escence. The conclusion the author has arrived at 

 is that the results of observation can only be ex- 

 plained by the formation of new molecules under the 

 action of the violet or ultra-violet rays. 



Investigations in various fields of research like- 

 wise show that a lowering in the refrangibility 

 of the spectrum of a body is accompanied by 

 the existence of heavier molecules. 



The problem also presents itself to account for 

 the growth of these molecular aggregates under 

 the influence of light and other sources of fluores- 

 cence. 



The experiments of Stokes and Becquerel on 

 the destructive influence of the infra-red and less 

 refrangible rays of the visible spectrum on phos- 

 phorescence indicate that the formation of the 

 molecular aggregates depends somehow upon the 

 wave-length of the exciting light. It also appears 

 that the formation of these molecules depends upon 

 the presence of nuclei ; and it is suggested that 

 their size would depend upon surface tension which 

 keeps the group together, as substances which 



