CONTENTS xiii 



CHAPTER XIII 



PHYSICAL METABOLISM 



PAGE 



The phenomenon of fluorescence — Discovered by Herschel — 

 Change of refrangibility discovered by Stokes — Work of 

 Lommel — Change of absorption — Description of experi- 

 ments on this — Views of 0. E. Guillaume and A. Cotton — 

 Negative results — The experiments of Nichols and Merritt 

 — Relation between absorption and the intensity of fluor- 

 escence — Inference to be drawn from these observations and 

 the change of refrangibility, the fluorescence being inde- 

 pendent of the period of the exciting light — Fluorescence 

 a building up and breaking down of molecules — Physical 

 metabolism 232 



CHAPTER XIV 



RADIATION AND MOLBCDLAB. A6GEEGATI0N 



Summarily the result of association and dissociation — Or more 

 or less complex molecular groups — Radiation from flames — 

 Tyndall's experiments on the emissive and absorptive powers 

 of gases —Spectra of oxygen — Repulsion between spheres of 

 molecular dimensions whilst radiating intensely — How 

 aggregates may preserve their identity — Catalytic action — 

 Effect of glycerine and gelatin on aggregation in fluorescent 

 bodies .... . . . 251 



CHAPTER XV 



ON THE FORMATION OF AGGREGATES OF LARGE MOLECULES 



The efiect of infra-red rays — Stokes' law reversed, or oalor- 

 escence — The function of a nucleus in phosphorescent bodies 

 — The efiect of surface tension on aggregation — Influence of 

 films — Chemical reaction in high vacua 



CHAPTER XVI 



PHOSPHORESCENCE AND MOLECULAR AGGREGATION 



Phosphorescence and catalytic action — Efiect of molecular 

 concentrations on freedom of corpuscles — Dependence of 

 phosphorescence upon free-paths and velocity of corpuscles 

 — Existence of separate phosphorescent molecules in liquids, 

 and of separate active molecules in luminous gases — That 

 separate large molecules exist in flames — The process of 

 catalysis and metabolism once more 278 



