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 light was first ap- 

 plied in this sense ; and we know that the solar 

 microscope may be brought into action at night by 

 means of the phosphoric light 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. 



