MEMOIR IX.] EFFECTS OF HEAT ON PHOSPHORESCENCE. 15 9 



MEMOIR IX. 



ON THE EFFECTS OF HEAT ON PHOSPH 



From the Philosophical Magazine, Feb., 1851. 



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CONTENTS: Experiment of Albertus Magnus. Degree of phosphores- 

 cence at different temperatures. The quantity of light a substance can 

 retain is inversely as its temperature ; the quantity it can receive is di- 

 rectly as the intensity and quantity of light to which it has been ex- 

 posed. Phosphorescent images of the moon. Action of ether waves. 

 Effects of cohesion. Reason that gases, liquids, and metals are non- 

 phosphorescent. 



IT has been already observed that the effect of heat 

 in promoting the disengagement of light is an old dis- 

 covery. Albertus Magnus remarked it in the case of 

 a diamond plunged into hot water. 



It is customary in later works which treat systemat- 

 ically on phosphorescence to group the different facts 

 under two heads 1st, phosphorescence produced by in- 

 solation ; 2d, by heat. An example of this is offered in 

 the standard work on chemistry by Gmelin. 



A division of this kind brings the whole subject into 

 confusion. It assigns different causes for things that are 

 essentially allied. It leads to the inference that as un- 

 der certain circumstances the sunlight or an electric 

 spark can make bodies glow, so under other circumstan- 

 ces heat will produce the same effect, and this wholly 

 independent of incandescence. 



But what are the facts? If a yellow diamond placed 

 upon ice be submitted to the sun, and then brought into 

 a dark room the temperature of which is 60, for a time 

 there is a glow, but presently the light dies out. If the 



