222 



Papers from the Department of Marine Biology. 



(3) The tidal currents. In the region of the Florida Keys the ebb 

 is south and the flow north. 



At Tortugas, the ebb flows through the northwest channel and 

 continues out through the southeast and southwest channels, with 

 a maximum speed of about 2 knots, as measured by Vaughan (1910, 

 1914), so that it does not go more than 12 miles before returning, and 

 hence does not reach the Gulf Stream. But it seems probable that a 

 considerable admixture of Gulf Stream water finally reaches Tortugas. 



The time the tide turned, starting south (high water), at Tortugas is 

 given in table 3 for July 1917. 



Table 3. 



RECORDS OF ALL STATIONS AND OF A TANK OF SEA-WATER. 



Table 4 gives the determinations of the surface water at station A 

 (fig. 4) on the eastern side of Loggerhead Key for the month of July 

 1917, and table 5 gives similar data of a tank of sea- water 4 by 6 by 4 

 feet for July 23-24. The unit of CO2 tension is one ten-thousandth of 

 a normal atmosphere of CO2 (760 mm. Hg). 



