i 3 2 SCIENCE PROGRESS 



3. It is a curious fact that we should be led to the third 

 conclusion directly from consideration of a very simple fact. 

 Taking the amount of coal estimated to be under the best 

 known areas, Great Britain for example, 1 if we suppose that 

 this represents the average distribution for all the continental 

 and "transitional" (i.e. shallow water) levels of the earth, we 

 arrive at a quantity of carbon which would be approximately 

 the chemical equivalent of the amount of oxygen now in the 

 atmosphere. We know that coal is the product of the great 

 water-plants 2 which flourished at a maximum in the so-called 

 Carboniferous period ; in other words, it was due to the splitting 

 up of carbon dioxide under leaf action. And it is supposed, as 

 other considerations suggest, that in subsequent times the give 

 and take of oxygen to and from the atmosphere has been main- 

 tained at something like the present balance. 3 Since we know 

 of no other adequate source of oxygen, it seems fair to conclude, 

 therefore, that antecedent to plant life the atmosphere was 

 practically devoid of this element. 



This view of an oxygenless atmosphere in former times was 

 put forth as early as 1845 by C. J. Koene of Brussels. It has 

 been supported in later times chiefly by T. L. Phipson, 4 J. Lem- 

 berg, 5 John Stevenson, Lord Kelvin 7 and Arrhenius 8 ; it would 

 seem to be a necessary postulate of any meteoritic theory of 

 earth origins, since, as noted, gaseous oxygen does not appear to 

 be a constituent of meteorites. A radically opposite view, of a 

 former enormous excess of oxygen, developed among others by 

 H. Lenicque, 9 is due to exclusive consideration of the chemical 

 side of the problem, without regard to the known geological 

 facts. It is incompatible with the existence of oxidisable 

 but unoxidised compounds, present in enormous quantities, 

 especially and particularly in the igneous rocks. As already 

 indicated, this would involve a very rapid absorption of oxygen 



1 Cf. the ingenious calculations of John Stevenson, Phil. Mag. 312, 50, 1900 ; 

 also Bischof, Verh. d. niederrhein. Ges.f. Naturk. 4 marz 1887. 



2 Walther, I.e. 306 ff. 



s Gregory, I.e. with citations of literature ; Eckardt, I.e. p. 8ff. 



* Chem. News, London, vols. 67-9, 1893-4. 

 i Cited after Clarke, I.e. p. 50. 



* I.e. 



7 Phil. Mag. 66, 47, 1899. 



8 Werden d. Welten, p. 50 (Leipzig, 1907) ; also in English translation. 



9 Mem. Soc. ingen. civils France ; October 1903, p. 346. 



