154 MAYOR— DETECTING OCEAN CURRENTS. 



. Thus according to my observations the averages for the shore 

 current the saHnity of which ranges from 30 to 33 grams in 1,000 

 grams of water, between Nova Scotia and northern Florida in win- 

 ter are : Temperature 6.7° C, sahnity 31.7, PH 8.05 and CO2 tension 

 2.5 ten-thousandths of an atmosphere, while similar data for the 

 Gulf Stream of salinity 36 at the same season between the Straits 

 of Florida and Cape Hatteras are : Temperature 22.3° C, salinity 

 36.35, PH 8.21, and COo tension 2.77. Thus the cold shore water 

 seems to be in a condition to absorb COo from the air, while the 

 warm Gulf Stream waters are more nearly in balance with the at- 

 mosphere. In summer when the shore current is warmed to about 

 22° C, its CO2 tension rises to be quite in balance with the atmos- 

 phere, as is indicated by McClendon's Table VII., p. 226, 1918. 



It is well known from the extensive work of Blackman and 

 Smith that photosynthesis about doubles in effect for 10° C. rise in 

 temperature, but due to the action of denitrifying organisms such 

 as Drew's Pseudomonas calcis the tropical waters are deprived of 

 nitrogen and can thus support only a meager plant life in compari- 

 son with that of colder regions. Thus McClendon found less than 

 o.oi mg., of nitrogen per liter as nitrates and nitrites at Tortugas, 

 Florida, while Raben, 1910, found more than ten times these 

 amounts in the North Sea ; and as shown by McClendon the tropical 

 ocean despite its high temperature can only eliminate a small part 

 of its free COo by photosynthesis due to the scarcity of plant life. 



Krog, 1904, calculated that if the average COo tension of the 

 ocean is the same as that of the air (about 0.0003 atmosphere), it 

 must contain twenty-seven times as much COo as the air. Thus if 

 the ocean gave off one tenth of its COo to the air the carbon dioxide 

 tension of the sea would sink to 0.0002 atmosphere. He found that 

 the COo in the air of Disko Island, Greenland, ranged from 0.00025 

 to 0.007, being high with winds from the north and west, and low 

 when the wind blew from the south and east. The turbid sea water 

 at Disko Island had a COo tension of o.oooi to 0.00035, while the 

 clear water in the same region had a tension of 0.00035 to 0.0006 

 atmospheres, thus apparently being lower than that of the surround- 

 ing air. 



Also the COo tension of the surface water between Cape Fare- 



