PRACTICAL CONSIDERATIONS. 199 
In cases of poisoning by phosphorus, the lumi- 
nosity of this substance in the dark is the princi- 
pal character by which chemists assure themselves 
of its presence in the intestines, etc., submitted to 
analysis. Mitscherlich, of Berlin, has invented an 
ingenious apparatus for this purpose. 
If we were acquainted with the circumstances 
which produced the phosphoric light described by 
Dr. Kane, and which enabled him to find the pis- 
tol so readily, it would be exceedingly useful to 
command at will such an evolution of light. 
As concerns Natural History, new sources of 
light employed in microscopical investigations are 
often attended with unexpected results. Such 
was the case when polarized hght was first ap- 
pled in this sense; and we know that the solar 
microscope may be brought into action at might by 
means of the phosphoric ight evolved by lime. 
I have known phosphorescence had recourse to in 
order to distinguish one plant from another. This 
was the case with two closely allied species of 
Rhizomorpha, which sometimes resemble each 
other extremely ; the one is however phosphores- 
cent at night, and the other devoid of this pro- 
perty. 
In Mineralogy the phosphorescent properties of 
fluor-spar, arsenic, lime, oxide of zinc, etc., ren- 
der it easy to detect their presence when sub- 
stances are heated before the blowpipe. 
