264 THE ORIGIN OF LIFE 



it is to phosphoresce, and organic compounds like 

 albumin become very phosphorescent if first ex- 

 posed to the temperature of liquid air. 



He found also that water is slightly phosphorescent, 

 even if pure, at low temperature ; but that when 

 slightly impure it is very phosphorescent, and as 

 we have concluded in the case of gases, foreign bodies 

 as slight impurities play a most important part in 

 the interactions giving light. These efiects of im- 

 purities in their relation to catalytic actions will be 

 considered later on. 



Experiments such as those of Lippmann on colour 

 photography show that it is actually possible to 

 obtain layers of such large molecules as we have 

 contemplated by stationary waves, and of the di- 

 mensions of the wave-length, since the distances 

 apart of the layers depends upon the wave-length 

 of the impinging light. The use of the word mole- 

 cules for the matter which contributes these layers 

 can of course be made use of only in an extended 

 sense, and for that reason we call them aggregates 

 of molecules, which is doubtless what they are, 

 although it may be permissible to call them " large 

 molecules." 



In the photographic plate they remain fixed, 

 whilst in a phosphorescent substance their presence 

 would be only more or less permanent. 



However, as the addition of glycerine or gelatin 

 to solutions of phosphorescent substances causes a 

 considerable increase in the duration of the phos- 

 phorescent light, this thickening of the solution 



