182 PHOSPHORESCENCE. 



light and heat. Hence, when the particles of a 

 body are shaken by percussion, friction, heat, 

 light, or decomposed by chemical action or by an 

 electric spark, these two effects (light and heat) 

 may be produced by the recomposition of the two 

 electricities, especially when the particles sub- 

 mitted to experiment are bad conductors. But as 

 these causes are precisely those which produce 

 phosphorescence, we are induced to admit the 

 identity of electric light and that of phospho- 

 rescence;* so much the more as the luminous 

 appearances are sensibly the same in both cases, 

 and as bodies, which are good conductors of elec- 

 tricity, in which the phenomena are rarely accom- 

 panied by emission of light, are also devoid of 

 phosphorescence " (Becquerel) . 



This theory, brought forward some years ago, 

 is hardly on a level with the present state of 

 science; and, indeed, Dr. Young's ideas on the 

 phosphorescence of solar phosphorus, appear to 

 me quite as near a satisfactory explanation. Dr. 

 Young admitted that the shining of the Bologna 

 stone, after it has received the rays of the sun, 

 greatly resembles the sympathetic sounds of musi- 

 cal instruments, which are agitated by other sounds 

 conveyed to them through the air. 



* It would not be impossible to prove this opinion to be true 

 or false, by submitting phosphoric light to spectrum analysis, as 

 I have stated before. For my own part, I am not inclined to 

 admit the fact ct, priori, in M. Becquerel's sense. 



