430 THE SCIENTIFIC PAPERS OF 



clear summer's day) for several hours, when upon again connecting 

 up to the inductorium, a discharge, apparently that of a hydrogen 

 vacuum, was obtained. This experiment being repeated furnished 

 unmistakable evidence, I thought, that aqueous vapour had been 

 dissociated by exposure to solar radiation. The C0 2 tubes gave, 

 however, less reliable results. Not satisfied with these qualitative 

 results, I made arrangements to collect the permanant gases so 

 produced by means of a Sprengel pump, but was prevented by 

 lack of time from pursuing the inquiry, which I purpose, however, 

 to resume shortly, being of opinion that, independently of my 

 present speculation, the experiments may prove useful in extending 

 our knowledge regarding the laws of dissociation. 



It should here be observed that, according to Professor Stokes, 

 the ultra-violet rays are in a large measure absorbed in passing 

 through clear glass, and it follows from this discovery that only a 

 small portion of the chemical rays found their way through the 

 tubes to accomplish the work of dissociation. This circumstance, 

 being adverse to the experiment, only serves to increase the value 

 of the result observed. 



Assuming, for my present purpose, that dissociation of aqueous 

 vapour was really effected in the experiment just described, and 

 assuming, further, that stellar space is filled with aqueous and other 

 vapour of a density not exceeding the ^^th part of our atmo- 

 sphere, it seems reasonable to suppose that its dissociation would 

 be effected by solar .radiation, and that solar energy would thus be 

 utilised. The presence of carbonic anhydride and carbonic oxide 

 would only serve to facilitate the decomposition of the aqueous 

 vapour by furnishing substances to combine with nascent oxygen 

 and hydrogen. It is not necessary to suppose that all the energy 

 radiated from the sun into space should be intercepted, inasmuch 

 as even a partial return of heat in the manner described would 

 serve to supplement solar radiation, the balance made up by abso- 

 lute loss. To this loss of energy must be added that involved in 

 keeping up the circulating movement of the gas, which, however, 

 would probably not be relatively greater than that concerned in 

 the tidal retardation of the earth's rotation. By means of the 

 fan-like action resulting from the rotation of the sun, the vapours 

 dissociated in space would be drawn towards the polar surfaces of 

 the sun, be heated by increase in density, and would burst into 



