.SYA WILLIAM SIE.ME.\S, F.R.S. 31! 



2. That these gaseous compounds are capable of being dissociated 

 by radiant solar energy while in a state of extreme attenuation. 



8. That the vapours so dissociated are drawn towards the sun in 

 consequence of solar rotation, are flashed into flame in the photo- 

 sphere, and rendered back into space in the condition of products 

 of combustion. 



Three weeks have now elapsed since I ventured to submit these 

 propositions to the Royal Society for scientific criticism, and it 

 will probably interest my readers to know what has been the 

 nut ure of that criticism and the weight of additional evidence for 

 or against my theory. 



Criticism has been pronounced by mathematicians and physi- 

 cists, but affecting singularly enough the chemical and not the 

 mathematical portion of my argument ; whereas chemists have 

 expressed' doubts regarding my mathematics while accepting the 

 chemistry involved in my reasoning. 



Doubts have been expressed as to the sufficiency of the proof 

 that dissociation of attenuated aqueous vapour and carbonic acid 

 is really effected by radiant solar energy, and, if so effected, 

 whether the amount of heat so supplied to the sun could be at all 

 adequate in amount to keep up the known rate of radiation. It 

 was admitted in my paper that my own experiments on the dis- 

 sociation of vapours within vacuous tubes amounted to inferential 

 rather than absolute proof ; but the amount of inferential evidence 

 in favour of my views has been very much strengthened since by 

 chemical evidence received from various sources ; and I will here 

 only refer to one of these. 



Professor Piazzi Smyth, the Astronomer Eoyal for Scotland, 

 has, in connection with Professor Herschel of Newcastle, recently 

 presented an elaborate paper or series of papers to the Royal 

 Society of Edinburgh " On the Gaseous Spectra in Vacuum 

 Tubes," of which he has kindly forwarded me a copy. It appears 

 from these memoirs that when vacuum tubes, which contain 

 attenuated vapours, have been laid aside for a length of time, 

 they turn practically into hydrogen tubes. In another very 

 recent paper presented to the Royal Society of Edinburgh, 

 Professor Piazzi Smyth furnishes important additional proof of 

 the presence of oxygen in the outer solar atmosphere, and gives an 

 explanation why this important element has escaped observation 

 by the spectroscope. Additional proof of the existence of oxygen 



