l6o ABIOGENIC ORGANIC-CHEMICAL EVOLUTION 



ing formations which serve to replenish the atmosphere with 

 carbon dioxide during all sorts of plutonic processes. It is 

 for this reason that the only carbon compound which is 

 present in quantitatively significant amounts in volcanic 

 gases and the volatile constituents of magma is CO2, while 

 hydrocarbons are present sometimes, but only as traces. It 

 was on the basis of such observations that many authors 

 (e.g."*") who had not taken into account the difference 

 between the conditions formerly present on the surface of 

 the Earth and those which now prevail, accepted carbon 

 dioxide as the primary compound from which all further 

 organic evolution proceeded. For example, H. Borchert^* 

 referred directly, in his discussion of the matter, to the com- 

 position of the volcanic gases of the Hawaiian islands and 

 also to the considerable preponderance of CO2 over co and 

 CH4 in the gases which emerge from the inside of the Earth 

 in molten formations and, when these crystallise, become part 

 of the atmosphere. 



But V. Vernadskir" in his Outlines of geochemistry had 

 already pointed out that the carbon dioxide which is formed 

 in enormous amounts at times of volcanic eruption and in 

 quiescent volcanic areas is ' juvenile ' only in the sense that 

 it originates from ' juvenile ' regions (deep layers of the crust 

 of the Earth or magmatic foci). Its appearance is, however, 

 due to the decomposition of previously formed carbonates, 

 which is brought about at the high temperatures of the deep 

 layers of the crust of the Earth and through the melting of 

 metamorphic formations (Fig. 12). 



Urey^° was also quite right when, in criticising Poole, he 

 pointed out that one cannot understand how carbon dioxide 

 could have been formed from the graphite, methane or car- 

 bides of the interior of the Earth under the reducing condi- 

 tions which existed on the primaeval Earth. 



Only by ignoring the changes which have come about on 

 the surface of the Earth since it became inhabited by organ- 

 isms, by mechanically transferring present conditions to the 

 remote past, can one explain the fact that many authors 

 writing on the subject of the origin of life based their argu- 

 ments on the assumption that carbon dioxide was the primary 

 compound of carbon. As a result of this they met with 



