OYSTER INVESTIGATIONS IN GEOEGIA 



83 



irregular and less than the A^elocity of the ebb current. The dura- 

 tion of flood and ebb current varied considerably. At the normal 

 stage of the river, both currents were of approximately equal dura- 

 tion ; with the rise of the river stage, the ebb current prevailed with 

 a corresponding decrease in the duration of flood. On August 23, 

 when the Altamaha River was at high stage, the flood current con- 

 tinued for only two hours. (Fig. 17.) 



Figure 15. — Surface currents during the tidal cycle at Doboy Island, August 

 30, 1928, spring tide 



In the spring of 1929 the direction of flow of the surface ebb cur- 

 rent was generally NNE., but varied slightly to NE., N., and N. by W. 

 The direction taken by the bottom ebb current followed that of the 

 surface current rather closely (Tables 9 and 10), except that at the 

 one point where the surface swung N. by W. the bottom current 

 swung N. 



