198 PRACTICAL CONSIDERATIONS. 
plied to so many useful purposes by engineers, 
astronomers, microscopical observers, etc. 
The same arguments might apply to the Hlec- 
tric Light; but it has not yet been proved that 
this is identical with phosphorescence, though 
such is the opinion of some philosophers, as we 
have already seen. 
Again, I have alluded, in the first part of this 
work, to the fact that houses freshly painted with 
lime-wash are frequently luminous at mght, though 
slightly, after exposure to the sun’s rays during 
the day. If, by chemical and physical research, a 
means were discovered capable of rendering this 
phosphoric ight more powerful, by employing sul- 
phides of calcium or barium, etc., and superadd- 
ing, if necessary, the action of an electric cur- 
rent when the sun is hidden by clouds, a street 
might be effectively illuminated by phosphorescent 
fete alone. 
The light of the iene or Fireflies, has for 
years been employed for hghting apartments, and 
in travelling, in the West Indies. 
Phosphorus dissolved in oil has been sometimes 
used asa night-hght. As long as the bottle which 
contains the liquid remains closed no light is seen ; 
but when opened the phosphorescence is sufli- 
ciently bright to enable us to read the hour upon 
a watch, etc. These luminous bottles were once 
much in vogue as useful curiosities. - 
