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 1s acidified with sulphuric acid, the light 
eiven out by the positive pole is red, whilst that 
emitted by the negative pole is violet. The hght 
seems to encase the wires and to repel the water, 
so as to prevent its contact with the metal. 
