406 Mr. J. Stevenson on the Chemical and 



is an altogether simpler and more credible hypothesis to 

 suppose that the oxygen was all in the combined condition at 

 one time ; and even the additional supposition that there was a 

 considerable amount of hydrogen or of hydrocarbon gases left 

 over in the atmosphere after all the oxygen had gone into 

 combination, is not at all incredible. 



A theory or supposition of this kind is no doubt somewhat 

 startling, but it is supported ly solar and stellar analogy in 

 the most emphatic manner. The sun and many other stars 

 contain, as is well known, large quantities of free hydrogen 

 gas, but no oxygen whatever has been found in any of them 

 by spectroscopic examination. This, of coarse, may be due 

 to the circumstance that oxygen, though present is, combined 

 in forms which do not reveal themselves to the spectroscope, 

 or that oxygen even when free is not readily observed in a 

 flame by means of the spectroscope. However that may be, 

 we know that there is a great abundance of free hydrogen 

 on the sun and many stars, while not a trace of free oxygen 

 has been observed with certainty as yet. 



Another observation of the same kind is that of Sir W. de W. 

 Abney, regarding the absorption spectra of the attenuated 

 gases which are supposed to be present in interstellar space. 

 He considered that his observations pointed to the existence 

 of the vapour of benzene, a well-known hydrocarbon, in these 

 highly vacuous regions. 



But there is additional evidence of this kind, and evidence 

 which brings the observation much nearer the earth itself, 

 viz., the circumstance that meteorites have been found which 

 contained occluded hydrogen. In all probability the meteorites 

 which have fallen on the earth previously travelled round the 

 sun in orbits not greatly differing from that of the earth, at 

 least as regards the average distance from the sun. We 

 should therefore, on the ordinary theories of the formation of 

 the solar system, naturally expect them to contain roughly 

 the same elements as the earth, and roughly also in the same 

 proportion. Now it is well-known that meteorites frequently 

 contain a large amount of metallic iron or iron carbides, and 

 similar oxidizable substances. Compounds containing oxygen 

 are no doubt also found, and sometimes in considerable 

 quantity, but there is never enough oxygen present to com- 

 pletely oxidize all the other elements. The composition and 

 mineralogical character of these compounds also seem to pre- 

 clude the existence of free oxygen on the meteorites or the 

 materials from which they are formed. Prof. H. Newton has 

 made the significant observation that they are very similar to 

 the minerals which are found on the earth in deep-seated 



