.S7A' WILL/AM SIEMENS, F.K.S. 299 



than might have been expected, whereas a complete solution of the 

 problem would be furnished by a theory, according to which the 

 radiant energy which is now supposed to be dissipated into space 

 jind irrecoverably lost to our solar system, could be arrested and 

 brought back in another form to the sun himself, there to continue 

 tin- work of solar radiation. 



Some six years ago the thought occurred to me that such a 

 solution of the solar problem might not lie beyond the bounds of 

 possibility, and although I cannot claim intimate acquaintance 

 with the intricacies of solar physics, I have watched its progress, 

 and have engaged also in some physical experiments bearing upon 

 the question, all of which have served to strengthen my confidence 

 and to ripen in me the determination to submit my views, not 

 without some misgiving, to the touchstone of scientific criticism. 



For the purposes, of my theory, stellar space is supposed to be 

 filled with highly rarefied gaseous bodies, including hydrogen, 

 oxygen, nitrogen, carbon, and their compounds, besides solid 

 materials in the form of dust. Each planetary body would in that 

 case attract to itself an atmosphere depending for density upon its 

 relative attractive importance, and it would not seem unreasonable 

 to suppose that the heavier and less diffusible gases would form 

 the staple of these local atmospheres ; that, in fact, they would 

 consist mostly of nitrogen, oxygen, and carbonic acid, whilst 

 hydrogen and its compounds would predominate in space. 



In support of this view it may be urged, that in following out 

 the molecular theory of gases as laid down by Clausius, Clerk 

 Maxwell, and Thomson, it would be difficult to assign a limit to a 

 gaseous atmosphere in space ; and, further, that some writers 

 among whom I will here mention only Grove, Humboldt, Zoellner 

 and Mattieu Williams have boldly asserted the existence of a 

 space filled with matter. But Newton himself, as Dr. Sterry Hunt 

 tells us in an interesting paper which has only just reached me, 

 has expressed views in favour of such an assumption. 



The history of Newton's paper is remarkable and very sugges- 

 tive. It was read before the Royal Society on the 9th and 16th 

 of December, 1675, and remained unpublished until 1757, when it 

 was printed by Birch, the then secretary, in the third volume of 

 his History of the Royal Society, but received no attention ; in 184C 

 it was published in the " Philosophical Magazine " at the sugges- 



