of the Surface Water of the Atlantic and Pacific. 



71 



Thus the facts seem to warrant the inference that easterly counter 

 currents, such as are found in about 5° N. latitude in the mid-Pacific 

 and possibly also the Guinea Stream of the tropical Atlantic, are 

 composed of water which has upwelled to the surface. 



Henderson and Cohn (1916, p. 621) conclude from laboratory 

 experiments that upon the whole, in most places and at most seasons, 

 carbon dioxide must be escaping from the sea into the air, although 

 they also state that the balance is doubtless restored by CO2 entering 

 the water from the air in the polar regions. These authors did 

 not consider the effect of photosynthesis by marine plants, which 

 McClendon afterward showed to be such an important factor. Were 

 it not for photosynthesis, it is probable that large quantities of carbon 

 dioxide would escape from the sea in the tropics, but, instead of this, 

 McClendon, Wells, and I find that the warm waters are nearly in 

 balance with the atmosphere. 



Table 5. 



My observations along the Atlantic coast between Nova Scotia 

 and Florida, from December to March, show also that the coastal 

 current during these cold months has a CO2 tension somewhat below 

 that of the atmosphere, and this may be due to the great concentration 

 of plant life in these cold waters. 



Thus, according to my observations, the averages for the shore 

 current, the sahnity of which ranges from 30 to 33, between Nova 

 Scotia and northern Florida in winter, are: Temperature 6.7° C, 

 salinity 31.7, Ph 8.05, and CO2 tension 2.5 ten-thousandths of an 

 atmosphere, while similar data for the Gulf Stream at the same season 

 between the Straits of Florida and Cape Hatteras are: Temperature 

 22.3° C, salinity 36.35, Ph 8. 21, and CO2 tension 2.8. Thus the cold 

 shore-water seems to be in a condition to absorb CO2 from the air, 

 w^hile the warm Gulf Stream waters are more nearly in balance with 

 the atmosphere. In summer, when the shore current is warmed to 

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

 atmosphere. 



It is well known, from the extensive work of Blackman and Smith, 

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

 ature, but the tropical waters are deficient in nitrogen and can thus 

 support only a meager plant life in comparison with that of colder 



