426 THE SCIENTIFIC PAPERS OF 



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 

 Maitieu Williams, have boldly asserted the existence of a space 

 filled with matter, and that Newton himself, as Dr. Sfcerry Hunt 

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

 has expressed views in favour of such an assumption. Further 

 than this, we have the facts that meteorolites whose flight through 

 stellar, or at all events through interplanatary space, is suddenly 

 arrested by being brought into collision with our earth, are known 

 to contain as much as six times their own volume of gases taken 

 at atmospheric pressure ; and Dr. Flight has only very recently 

 communicated to the Eoyal Society the analysis of the occluded 

 gases of one of these meteorolites taken immediately after the 

 descent to be as follows : CO a , 0'12 ; CO, 31'88 ; H, 45'79 - t 

 CH 4 , 4-55 ; N, 17-66. 



It appears surprising that there was no aqueous vapour, con- 

 sidering there was much hydrogen and oxygen in combination with 

 carbon, but perhaps the vapour escaped observation, or was ex- 

 pelled to a greater extent than the other gases by external heat 

 when the meteorolite passed through our atmosphere. Opinions 

 concur that the gases found occluded in meteorolites cannot be 

 supposed to have entered into their composition during the very 

 short period of traversing our atmosphere, but if any doubt should 

 exist on this head, it ought to be set at rest by the fact that the 

 gas principally occluded is hydrogen, which is not contained in 

 our atmosphere in any appreciable quantity. 



Further proof of the fact that stellar space is filled with gaseous 

 matter is furnished by spectrum analysis, and it appears from 

 recent investigation, by Dr. Huggins and others, that the nucleus 

 of a comet contains very much the same gases found occluded in 

 meteorolites, including " carbon, hydrogen, nitrogen, and probably 

 oxygen," whilst, according to the views set forth by Dewar and 

 Liveing, it also contains nitrogenous compounds such as 

 cyanogen. 



Adversely to the assumption that interplanetary space is filled 

 with gases, it is urged that the presence of ordinary matter would 



