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induces combustion of the oxygen. The liberated hy- 

 drogen and oxygen fly off to the sun, and of their re- 

 maining parts the combusted oxygen, united with azote 

 in the form of carbon, sinks to the earth ; while the hy- 

 drogen is converted into that fine vapour which, in cu- 

 mulus and feathery clouds, floats in the air above the earth. 



Thus what appears to be a mere mixture of atmos- 

 pheric gases is in reality a struggle; though not, as we 

 shall see afterwards, a blind ruinous contest. We find 

 in this struggle a perfectly reasonable principle (a c t i o 

 and r e a c t i o) of cosmic interaction and mutual help 

 between the spheres. The friction of oxygen and azote 

 supplies the different lights which shine from different 

 stars. 



But if the planets, and of course amongst them our 

 earth are shining bodies, how is it that we who live on 

 the earth cannot remark this light? 



I will try by an illustration to explain why. Imagine 

 that you have lain down at the bottom of a pond. The 

 weight of your body will have squeezed out the air from 

 under you, and this will rise to the surface in bubbles 

 which to you, as you lie among the weeds under the 

 water, will seem like little dark balls ascending. But if 

 at this time any-one standing on the shore should be 

 watching these bubbles they will appear to such an 

 observer of a luminous silver hue. The air-bubbles are 

 therefore dark beneath and light above. Why so? Because 

 the upper part pressing against the water has produced 

 a slight but yet perceptible combustion of the oxygen 

 contained. 



The wave-like ascension ot the lighter gases in the 

 air is ve^ noticeable to the naked eye on bright hot 

 summer days. 



If we could raise ourselves to a certain distance above 

 our atmosphere we should then see an endless multitude 

 of oxo-hydrogen bubbles illuminated by their friction 

 against the heavier azote. This is the cause of planetary 

 light. 



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