152 MAYOR— DETECTING OCEAN CURRENTS. 



above that of the water farther off the coast. Thus a PH of 7.85 

 at 10.5° C, and COo tension of 5.4 ten thousandths of an atmos- 

 phere were observed 54 miles ofif Golden Gate, San Francisco, on 

 May I, 1917; and somewhat similar conditions were seen off Van- 

 couver in September, 1918. 



An up- welling of deep water due to off shore winds has also been 

 demonstrated by Bigelow, 1917, p. 241 ; along the coast of New Eng- 

 land north of Cape Cod, but this effect is neither so marked nor so 

 constant in the shallow water along our Atlantic seaboard as it is 

 off the abrupt slope of the Pacific coast. Indeed Bigelow, 191 5, 

 191 7, has shown that the cold water which drifts down the Atlantic 

 coast from Nova Scotia to Florida is chiefly derived from the Gulf 

 of St. Lawrence and receives accessions from surface drainage and 

 from rivers along its whole course. 



McClendon, 191 7, 1918, showed that the COo tension of surface 

 water at Tortugas and in the Gulf Stream, is on the average about 

 in balance with the atmosphere, 30 determination indicating that 

 the pressure of carbon dioxide of the air ranges from 2.8 to 3.5 ten- 

 thousandths of an atmosphere, while that of the surface water of 

 the Tortugas lagoon on the east side of Loggerhead Key ranged 

 from 2.(i to 3.5 ten-thousandths of an atmosphere, and that of the 

 Gulf Stream from Key West to Cape Hatteras was from 3.2 to 3.5. 

 McClendon also found that photosynthesis by marine plants in sun- 

 light is a very important factor in controlling the hydrogen-ion con- 

 centration of the water of shallow lagoons or tide pools where the 

 bottom is covered with sea weed ; for the plants reduce the COo, 

 thus setting free oxygen and causing the water to become highly 

 alkaline. For example, while the PH of the sea around the Tor- 

 tugas is about 8.22 that of the lagoon rose at times to 8.35 by day 

 and sank to 8.18 at night, and the hot shallow lagoon of the Mar- 

 quesas, Florida, had a PH of 8.46 accompanied by precipitation of 

 calcium carbonate. McClendon was, however, unable to find any 

 appreciable diurnal range in hydrogen-ion concentration of the sur- 

 face water in the open sea nor can I detect it from my studies in the 

 Atlantic and Pacific. 



Also Wells, 1918, p. 6, shows that the water of the Gulf of Mex- 

 ico contains about 0.092 grams of CO2 per liter and its surface 



