THE ORIGIN OF ORGANIC MATTER 45 



ceeded. This is in harmony with the fact that the pH of the great oceans 

 to the depth penetrated by light is more constant than the CO2 tension, 

 the pH varying from about 8.0 to 8.25 and the CO, tension from about 

 0.00015 to 0.0005 atmosphere. The sea may be compared to the body of 

 one of the higher vertebrates. The mammal regulates the pH of the 

 blood through the action of the respiratory center. The sea regulates the 

 pH of its surface-water most probably through the action of seaweed. 

 The limit in the supply of oxygen probably prevents animal life from 

 getting the upper hand temporarily and thus endangering the communal 

 life in the sea. 



"It seems probable that seaweeds regulate the CO2 of the atmosphere. 

 The gaseous exchange between sea and air is necessarily at the surface 

 and is comparatively slow. Bohr observed that the absorption of CO2 

 from an atmosphere of the pure gas by CO.; — free water that is stirred 

 (probably more vigorously than the sea ever is) is about 0.1 cc. per 

 square centimeter of surface per minute. Since the difference in COo 

 tension between air and sea seems never to exceed 0.02 per cent of that 

 in Bohr's experiment, except in the polar regions, the rate of diffusion 

 would not exceed 0.00001 cc. per square centimeter per minute or 0.1 cc. 

 per square meter per minute in a storm, and necessarily much less in calm 

 weather on account of the lessened rate of stirring at the surface. When 

 we consider the volume of the sea and air compared to the sea-air surface, 

 the fact becomes intelligible that the CO2 in the air is relatively constant 

 (3 per 10,000) in the different regions of the world where it has been 

 accurately measured, whereas the CO2 tension of the sea-surface varies 

 from 1.5 to 5 per 10,000. The air is stirred more rapidly than the sea, 

 and the CO2 of the air seems to be determined by an equilibrium between 

 gain in CO2 over some regions of the sea-surface and loss over others. 

 The partial pressure of CO2 in the air is therefore the average CO2 

 tension of the sea-surface. The burning of billions of tons of coal per year 

 is probably changing the CO2 content of the sea and of the rocks and 

 not of the atmosphere." 



McClendon's analysis of the relation of the carbon dioxide in the 

 atmosphere and in the sea is much more thorough than that of Reinau. 

 McClendon points out that Krogh's results show that the carbon dioxide- 

 tension of sea-water increases with depth and that the tension of the sea- 

 surface is not in equilibrium with the air. This is also evident from the 

 work of Schulz already cited. Moreover, the carbon dioxide-tension of 

 sea-water varies; Krogh found it to vary from 1.5 to 3 per 10,000 in 

 the North Atlantic and McClendon from 3.3 to 4.7 per 10,000 at Tortugas 

 near the Gulf Stream. McClendon assumes that the water maintains a 

 relatively constant carbon dioxide-content and that on its flow northward 

 the carbon dioxide-tension decreases with the lower temperatures. In 

 general it would appear that McClendon's investigations support the gen- 

 eral theory of Schlossing. 



It has been assumed, on the basis of some analytical data, that there 



