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 m 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, 
oreatly resembles the sympathetic sounds of musi- 
cal instruments, which are agitated by other sounds 
conveyed to them through the air. 
* Tt 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 @ priori, in M. Becquerel’s sense. 
