of the Surface Water of the Atlantic and Pacific. 67 



the numerous algse growing over the floor of the reef-flat. In fact, 

 the CO2 tension in this impounded water was reduced to 0.8 ten- 

 thousandth of an atmosphere, whereas in the sea-water outside the 

 reef-flat it was 2.7 ten-thousandths. 



The Ph of sea-water is also lowered by fresh water pouring out 

 from rivers or brackish bays, and one observes this effect as one passes 

 the entrance to Delaware Bay, the Chesapeake, New York Harbor, 

 or Long Island Sound. The water from these bays, and especially 

 from New York Harbor, is more or less charged with decomposing 

 animal matter derived from sewage which drifts southward along the 

 coast. Such water is low in salinity and laden with carbon dioxide, 

 which lowers its Ph. Thus, off Barnegat, New Jersey, at 10'' 15"' 

 a. m. on June 25, 1919, the water showed 8.06 Ph at 19.5° C, and its 

 calculated CO2 tension was 4.2 ten-thousandths of an atmosphere; 

 so it must have been discharging CO2 into the air. Similarly, off 

 Golden Gate, San Francisco Harbor, the water on May 1, 1917, was 

 7.85 Ph at 10.5° C., and its CO2 tension was apparently 5.4 ten- 

 thousandths of an atmosphere. In both these cases the water was 

 discolored and evidently contained decomposing land waste. Dr. R. 

 P. Cowles tells me that he found the Ph of the bottom water of 

 Chesapeake Bay to range from about 7.75 to about 7.28. 



The dull-gray-green water that creeps down the coast of the United 

 States from the Gulf of St. Lawrence southward is about 8.0 to 8.1 

 Ph, while the deep-blue water of the Gulf Stream is 8.2 to 8.24. The 

 dull color of this shore water may to some degree be due to pelagic 

 plant life, but it is discolored in greater measure by the drainage and 

 waste from the thickly inhabited shore. One could readily ascertain 

 when the ship passed out of the Gulf Stream into the shore current 

 or vice versa by simply observing the sudden change in the Ph from 

 about 8.22 to 8.1 or less when one entered the shore current; but this 

 method is not likely to be of use in navigation, for the change in the 

 color of the water itself is equally good as an indication, and, moreover, 

 the soundings on this gradually shelving shore are so characteristic 

 and reliable that they alone afford good information respecting the 

 position of the ship. 



Along the Pacific coast of the United States the upwelUng of deep 

 water which has been demonstrated by McEwen (1910, 1918, etc.) 

 lowers the temperature and brings water rich in CO2 to the surface, 

 thus lowering the Ph, but this water with a low Ph of about 8.0 may 

 extend for 300 miles or more offshore; so in this region we could not 

 be certain of the close proximity of the coast merely by observing 

 a lowering of the Ph of the water. 



The most remarkable upwelling of cold, deep water to the surface 

 is encountered in the mid-Pacific, at or near the heat equator, which 

 ranges from near the geographical equator to about 5° N. latitude. 



