Brown. — The Maintenance oj the Sun's Heat. 399 



Let ine, in conclusion, sum up the main conditions of this 

 hypothesis : — 



(1.) That aqueous vapour and carbon compounds are 



present in stellar or interplanetary space. 

 (2.) That these gaseous compounds are capable of being 

 dissociated by radiant solar energy while in a state 

 of extreme attenuation. 

 (3.) That these dissociated vapours are returned to the 

 sun, and exchanged for recombined vapours by the 

 centrifugal action of the sun. 

 As Sir W. Siemens has remarked : "If these conditions could 

 be substantiated, we should gain the satisfaction that our solar 

 system would no longer impress us with the idea of prodigious 

 waste through dissipation of energy into space, but rather that 

 of well-ordered, self-sustaining action, capable of perpetuating 

 solar radiation to the remotest future." 



