EFFECTS OF HEAT ON PHOSPHORESCENCE. [MEMOIR IX. 



condition of cohesion characteristic of the solid state, and 

 the parts of which move freely among each other, phos- 

 phorescence cannot take place, for it depends on the in- 

 fluence that cohesion has had in restraining the vibra- 

 tory movements. 



Further, the condition of opacity does not permit phos- 

 phorescence to be established. The exciting ray cannot 

 find access to disturb the interior layers of the mass, and 

 even if it did, and phosphorescence ensued, how could 

 we expect to be able to discover it through the impervi- 

 ous veil of the superficial layers ? The light of the most 

 brilliant phosphorus cannot be seen through the thin- 

 nest gold-leaf. Its intensity is vastly too small. These 

 are the reasons that no one has ever yet succeeded in 

 detecting phosphorescence in metals and black bodies. 



It will be gathered from this explanation that I am 

 led to believe that all the facts of phosphorescence can 

 be fully explained on the principles of the communica- 

 tion of vibratory motion through the ether; that as upon 

 that theory an incandescent body maintained at incan- 

 descence would eventually compel a cold body in its 

 presence to come up to its own temperature by making 

 its particles execute movements like those of its own, so 

 the sunshine or the flash of an electric spark compels a 

 vibratory movement in the bodies on which its rays fall ; 

 that these vibrations are interfered with by cohesion in 

 the case of solids, but that they are instantly established 

 and almost as instantly cease in the case of liquids and 

 gases ; that reducing the cohesion of a solid by raising 

 its temperature permits a resumption of the movement ; 

 and that the condition of opacity, whether metallic or 

 otherwise, is a bar to the whole phenomenon. 



