162 EFFECTS OF HEAT ON PHOSPHORESCENCE. [MEMOIR IX. 



can receive is directly as the intensity and quantity of 

 light to which it has been exposed. 



(With respect to the light of the moon, I have suc- 

 ceeded in obtaining an image of that satellite on Canton's 

 phosphorus, by the aid of a concave metallic mirror.) 



The various facts herein cited indicate that when a 

 ray of light falls on a surface, it throws the particles 

 thereof into vibration. An examination of the action of 

 the differently colored rays dispersed by a prism shows 

 that in general the greater the frequency of vibration 

 of the impinging ray, the more brilliant is the phosphor- 

 escence. But in such a prismatic examination we have 

 constantly to bear in mind the disturbing agencies which 

 are present, and especially the antagonizing effects of 

 heat ; that this determines the amount of light that a 

 phosphorus can receive, and also the rate of its subse- 

 quent extrication. In Memoir V., p. 87, I have shown 

 how the photographic action of light betrays the general 

 principle of an interference of vibratory movements, and 

 the production of antagonizing results in different parts 

 of the solar spectrum. An argument is there brought 

 forward to the effect that as the violet end produces 

 phosphorescence and the red extinguishes it, this is a 

 proof of opposition of action. In explaining this fact, 

 M. E. Becquerel supposes the darkening power of the 

 red rays to be due to the more rapid disengagement of 

 the phosphorescence by reason of the heat produced by 

 those rays, arid the apparent antagonization is not at- 

 tributable to the supposition of vibratory movements of 

 light rays of different frequency, but to the relations of 

 caloric and light. The force of this explanation, how- 

 ever, disappears when it is understood that light and 

 heat, the chemical and phosphorogenic rays, are, accord- 

 ing to the principles of the able experimenter, all mani- 

 festations of the same agent. It avails us nothing to say 



