THE ORIGIN OF ORGANIC MATTER A7 



from the earth. However, of none of these sources can an approach at 

 quantitative estimation be made. 



More accurate estimations can be made of carbon dioxide produced 

 through the combustion of mineral fuels. A detailed compilation of the 

 world's coal production for 1920 has been made by Sievers." According 

 to these figures the annual production of coal amounted to a total of 

 1,317,000,000 metric tons (2204 lbs.) or 1,317 X 10' kilograms. This in- 

 cludes anthracite, bituminous and lignite or corresponds at the most to 

 about 70 per cent carbon which when burned would give about 338 X 10^° 

 kilograms of carbon dioxide. Thus we have 338 X 10^° kilograms car- 

 bon dioxide from the burning of coal compared to the 21 X 10^* kilo- 

 grams of carbon dioxide in the atmosphere, or an annual production of 

 0.16 per cent of the existing carbon dioxide. At this rate, other condi- 

 tions remaining the same, it would take about 650 years to double the 

 concentration of carbon dioxide in the atmosphere. ^- 



If the amount of carbon dioxide produced annually by the burning of 

 coal were distributed through the entire atmosphere it would exert but 

 a very slight effect and could not be detected by our present methods of 

 analysis. It is possible, however, that the mixing above about 100 meters 

 is slow, so that it may be expected that the carbon dioxide-concentration 

 near large industrial centers is higher. 



Coal has been used on a large scale for only about one hundred years. 

 If the rate of increase in consumption continues it might be expected 

 that this would result in an accumulation of atmospheric carbon dioxide. 

 On the other hand such an increase in carbon dioxide-content of the 

 atmosphere would result in augmented photosynthetic activity, which in 

 turn would tend to reestablish the equiUbrium. To what extent such an 

 increase in carbon dioxide-content would be noticeable in the vegetation 

 of the earth it is difficult to calculate. 



Increase in the rate of photosynthesis is about directly proportional to 

 increase in carbon dioxide-concentration under what may be termed natural 

 conditions. That is, for instance, with bright sunlight, at 20-25°, and 

 ample water supply a plant will about double its photosynthetic rate when 

 the carbon dioxide concentration is raised from 0.03 to 0.06 per cent. 

 However, the influence of external factors on the rate of photosynthesis 

 is very complex, as will be shown later ; moreover, photosynthesis is but 

 one factor affecting the development of a plant, so that it is very difficult 

 to make predictions regarding the final effect of any single factor. More- 

 over, an increase in the carbon dioxide-content of the atmosphere would 

 in time be largely equalized by the influence of the sea. 



During the last few years there has been much discussion and specula- 



■^Sievers, E. G., Gas Age Record, 51, 757-761 (1923). 



"'The annual coal consumption has been constantly increasmg so that various 

 older estimations are at slight variance with this figure. Krogh, Meddelelscr om 

 Groenland. 26, 419 (1904). Van Hise, Mon. U. S. Geol. Survey, 47, 964 (1904^ 

 Dittmar, Challenger Report, Vol. 1, pt. 2, 954. Chamberlm, Jour. Geol., 7, 6b2 

 (1899). 



