PHOSPHORESCENCE. “1 
a greenish-yellow phosphorescence. Dolomite, 
Aragonite, and some specimens of diamond, shine 
with a brilliant, white, phosphoric light. 
In the same manner, the colour of a flame de- 
pends upon the nature of the body that burns. 
Thus, carburetted hydrogen and sodium burn with 
a yellow flame, oxide of carbone with a blue 
flame, potassium and cyanogen with a purple 
flame, etc. 
Pearsall, Brewster, Dessaignes, and Becquerel 
have studied this subject. It appears to me very 
evident that the same substance may slightly 
differ in the colour of its phosphorescence, ac- 
cording to the manner in which the latter is 
prepared or excited. 
Concerning colours and tints, we should, in 
general, be careful in admitting them too exclu- 
sively, for there are scarcely two persons who will 
entirely agree upon the denomination of any tint 
that is not one of the striking colours of the solar 
spectrum. 
