l62 ABIOGENIC ORGANIC-CHEMICAL EVOLUTION 



in the form of infra-red radiations. The rest is reflected 

 unchanged into space. ^^ 



According to A. E. H. Meyer and F. O. Seitz,^^ 6-3 per 

 cent of all the solar radiation reaching the outermost layers 

 of the atmosphere is in the form of ultraviolet radiation 

 having a wavelength between 4,000 and 3,150 A, while that 

 having a wavelength of less than 3,150 A amounts to only 

 about 0-6 per cent. On the basis of direct measurements 

 obtained by sending rockets to great heights, however, J. A. 

 Sanderson and E. O. Hulbert^* give the intensity of the ultra- 

 violet radiation (from 4,000 A downwards) as five times 

 greater, namely 4-8 x 10-° kcal/year. 



As early as 1913 B. Moore,^^ proceeding from A. Baeyer's 

 theory of photosynthesis, put forward the idea that the pre- 

 requisite for the development of the organic substances neces- 

 sary to life was the formation of formaldehyde from the 

 primaeval carbon dioxide as the result of the action of solar 

 ultraviolet radiations. We find this same idea later in the 

 writings of P. Becquerel,^*^ J. B. S. Haldane," and, especially, 

 in a number of works by A. Dauvillier^* in which he elabor- 

 ates his photochemical theory of the origin of life. It was 

 shown, long ago, that carbon dioxide gives a series of absorp- 

 tion bands in the ultraviolet region of the spectrum from 

 1,710 A downwards. In absorbing these radiations it splits 

 to form CO and o (some of which finally appears as ozone). ^^ 



In the presence of water which is undergoing ultraviolet 

 photolysis we may suppose that CO2 could be reduced by the 

 hydrogen according to the equations : 



2H20->2H2-l-02 



2H2 -I- C02-^CH20 + H2O 



H,0 -I- COo-^CHoO + O2 



H. Thiele,*" however, did not find formaldehyde when he 

 submitted mixtures of hydrogen and carbon dioxide to ultra- 

 violet irradiation ; on the other hand, D. Berthelot and H. 

 Gaudechon," and later A. Coehn and G. Sieper,^^ established 

 that a small amount of formaldehyde is formed under these 

 circumstances. C. Zenghelis*^ also described experiments in 

 which carbon dioxide gas was reduced by hydrogen under 



