PRACTICAL CONSIDERATIONS. 197 
phosphorescent substance, to the heat, or, rather, 
to the chemical and electrical action, engendered 
during the combustion of hydrogen by oxygen 
gas. I have indeed been able to show by direct 
experiment that heat has not so much to do with 
the production of this intense hght as is generally 
supposed. 
If a piece of borax be heated before the blow- 
pipe, it melts when it has attained a red heat. If 
it be now allowed to cool and a little lime sprinkled 
over it, on applying heat a second time, the hme 
becomes vividly phosphorescent long before the 
borax is at all affected by the heat. It 1s there- 
fore evident that lime glows vividly with phos- 
phoric light long before its temperature has at- 
tained what is termed a red-heat. 
In the case of the Drummond Light and the 
phosphorescence of lime before the blowpipe, 
electricity may probably be the force which in- 
duces phosphorescence, since Grove (in 1854) has 
shown that the blowpipe flame gives rise to a very 
marked electric current; a number of jets ac- 
tually enabled the author to form an electric bat- 
tery of a certain intensity. Now, when the flame 
of oxygen and hydrogen gases is employed, the 
electric action must naturally be far more con- 
siderable than with a simple blowpipe flame. 
Hence the vivid phosphoric light which bears the 
name of Mr. Drummond, and which has been ap- 
