THE ORIGIN OF ORGANIC MATTER 39 



least a little knowledge of chemistry would have been of great assistance 

 to the exi:)erimenter, both in the choice of method and in the necessary 

 manipulations." 



Many years ago Regnault ^^ inaugurated an extensive international 

 investigation of the composition of the atmosphere. While the results 

 from this elaborately planned cooperative investigation were considerably 

 curtailed by the political disturbances existing in Europe at the time, they 

 are sufficient to demonstrate the value of such an undertaking. With the 

 advance in methods of analysis, of communication and of transportation 

 a similar undertaking now ought to be capable of execution and would 

 certainly justify itself. 



If photosynthesis actually has an appreciable influence on the carbon 

 dioxide content of the atmosphere, this could only be detected because 

 of imperfect and slow mixing of the gases of the air.^^ As nearly as can 

 be calculated there are about 2.2 X 10^^ tons (about 2 X 10^^ kilograms) 

 of carbon dioxide in the atmosphere. The total photosynthetic carbon 

 dioxide consumption can be put at about 54 X 10^- kilograms per year on 

 the basis of the calculations of Sachs given below. The annual consump- 

 tion therefore would be roughly only one fiftieth of the total supply of 

 atmospheric carbon dioxide. These figures are obviously very rough, but 

 indicate that if perfect mixing took place, the difference in carbon dioxide 

 concentration of the atmosphere, due to photosynthesis, would be so slight 

 that it could not be detected by analyses. Day and night variations in 

 carbon dioxide content, if they exist, are therefore probably due to a 

 combination of local conditions. On the other hand, with no wind, when 

 there is imperfect mixing it is highly probable that densely vegetated 

 areas show a carbon dioxide content below the "normal." 



A larger reservoir of carbon dioxide than the atmosphere is the sea.^* 

 Sea-water contains approximately 50 cc. of carbon dioxide per liter, but 

 varies with the depth at which the water is drawn. Moreover, the oceans 

 comprise fully 70 per cent of the surface of the earth, so that they play 

 an important role in the carbon dioxide cycle. In absolute amount also 

 the sea contains considerably more carbon dioxide than the atmosphere ; 

 the latter contains approximately 2100 billion kilograms while the former 

 contains about 16,000 billion kilograms, though these figures can be taken 

 only as approximations. Different estimates give the oceans eighteen to 

 twenty-seven times as much carbon dioxide as the atmosphere. 



Just how great are the potentialities of the sea for food it appears' 

 difficult to determine. In limited areas the sea produces as much or slightly 



*' Regnault, Ann. Chim. ct Phys. Ill, 36, 385 (1852). 



^ Clarke, Data of Geo-chemistry. Bui. U. S. Geological Survey No. 770, 1924, 

 p. 50. 



''Krogh, A., Compt. rend., 139, 896 (1904). Krummel, O., Handb. der Ozeanog- 

 raphie. Vol. I, 312 (1923). Schulz, A., Naturwissenschaften, 12, 105-113, 126-133 

 (1924). Politzsch, S., Compt. rend, dcs travaux du Laboratoire de Carlsberg, 11, 

 199 (1916). Wells, R. C, U. S. Geol. Survey, Professional Paper IZQ-A, 1-16 

 (1918). 



