CHAPTER, Val. 
DURATION, INTENSITY, AND COLOUR OF PHOS- 
PHORIC LIGHT IN MINERAL BODIES. 
THe duration, the intensity, and the colour of 
phosphorie light produced by mineral substances, 
depend upon the nature of the phosphorescent body. 
I shall mention only a few examples of colour. 
The most general tint of light is that seen in the 
glow-worm and other phosphorescent animals, of 
which we shall speak hereafter; it is a greenish- 
yellow light, at times approaching to whiteness. 
Some bodies however appear, during their phos- 
phorescence, to emit light which differs a little 
from this as to its colour. Certain marbles and 
amber (succinum) give a phosphorescent leht of 
a golden yellow; some specimens of fluor-spar, 
arseniate of lime, and chloride of calc1um, emit a 
greenish hght; other varieties of fluor-spar pro- 
duce a bluish-violet radiation, and that which is 
called Chlorophane gives a green phosphorescence. 
Oriental garnet shines with a reddish phosphores- 
cence, whilst Harmotome (a sort of zeolite) gives 
