OF GASES, ETC. 43 



duction of light that takes place when water is 

 being decomposed by the electric current, after 

 being rendered a good conductor of electricity by 

 the addition of sulphuric acid or potassa. When 

 forty Bunsen's elements are employed, the water 

 is rapidly decomposed, and its temperature con- 

 siderably raised, but a moment comes when the 

 platinum wires plunging into the liquid become 

 suddenly luminous, and the decomposition of the 

 water ceases as suddenly. In this case, when the 

 water is acidified with sulphuric acid, the light 

 given out by the positive pole is red, whilst that 

 emitted by the negative pole is violet. The light 

 seems to encase the wires and to repel the water, 

 so as to prevent its contact with the metal. 



