l66 ABIOGENIC ORGANIC-CHEMICAL EVOLUTION 



carbon dioxide to methane, whicli later polymerises to form 

 ethane and other compounds of higher molecular weight. 



W. M. Garrison, D. C. Morrison, J. G. Hamilton, A. A. 

 Benson and M. Calvin'' ° have recently published their studies 

 on the reduction of carbon dioxide in aqueous solutions 

 under the influence of ionising radiations. In their experi- 

 ments these authors proceeded from the assumption that the 

 formation of organic substances on the primaeval Earth was 

 achieved by the reduction of carbon dioxide under the in- 

 fluence of ionising radiations. To test this assumption they 

 submitted aqueous solutions of carbon dioxide to the action 

 of a stream of helium particles in a cyclotron and were able 

 to show definitely that formic acid and formaldehyde were 

 present among the products of the reaction. 



Phenomena of this kind may, of course, occur in the crust 

 of the Earth at present to a very limited extent, but under 

 the reduced conditions of the primaeval Earth they could 

 hardly have been of decisive significance owing to the small 

 amounts of carbon dioxide present there. 



All the sources of energy which we have enumerated (ultra- 

 violet and cosmic radiation, electric discharges and radio- 

 active breakdown) must have played important parts in the 

 early history of our planet, not only by bringing about reduc- 

 tion of carbon dioxide (which was scarcely present in large 

 amounts) but by transforming hydrocarbons which were, at 

 that time, the most abundant carbon compounds. The chemi- 

 cal evolution of the hydrocarbons could have been accom- 

 plished simply on the basis of their own energy potentials, 

 but the practical realisation of these potentialities was greatly 

 facilitated by the presence of supplementary sources of 

 energy. Short-wave ultraviolet radiation, silent electric dis- 

 charges and a-particles brought about specific transforma- 

 tions of organic molecules by stages, with the formation of a 

 series of intermediate compounds. We must bear in mind 

 that the hydrocarbons and their derivatives which were 

 originally formed in the lithosphere, where the temperature 

 and pressure may have been comparatively high, afterwards 

 migrated, for the most part, into a moist atmosphere, the 

 various layers of which were subjected to cold and the action 

 of light and electric discharges, and that the products which 



