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 light 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 lime 

 becomes vividly phosphorescent long before the 

 borax is at all affected by the heat. It is 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- 



