MEMOIR XXIIL] RAYS OF INCANDESCENT LIME, ETC. 323 



It is still more curious that a number of these latent 

 images may co-exist on the same surface. Provide a 

 phosphorescent surface on which the latent image of a 

 key impressed a day or two before by a voltaic discharge 

 is known to exist. Take some other object, as a metal 

 ring, and setting it before the surface, discharge at a 

 short distance a Leyden-jar. The phosphorus shines all 

 over, save on those portions shaded by the ring; it ex- 

 hibits, therefore, an image of that body. This image 

 soon fades away and totally disappears. Set the plate 

 now upon a piece of warm iron ; it soon begins to glow, 

 and the image of the ring is first reproduced, and as it 

 declines away the spectral form of the key gradually un- 

 folds itself, and after a time it totally vanishes. 



A series of spectral images may thus exist together 

 on a phosphorescent surface, and after remaining there 

 latent for a length of time, they will come forth in their 

 proper order on raising the temperature of the surface. 



The idea that phosphorescence is merely the light of 

 an electric discharge from particle to particle seems to 

 me wholly incompatible with such results. 



