240 bulletin: museum of compakative zoology. 



Gulf was evident from our early work there (1914a), Gulf salinity 

 being far too low. And on the cruise of 1913 we failed to find any 

 upwelling of this sort west of Cape Cod (1915, p. 260); a generaliza- 

 tion which can now be extended to the whole slope from Cape Cod 

 east to Halifax at least in summer; for we found none of the criteria, 

 e. g., lowered surface temperature, and ^•ertical uniformity of salinity 

 down to the level from which upwelling takes place, which would be- 

 tray such a process. On the contrary, the abyssal water all along the 

 slope, from off INIarthas Vineyard to the Eastern Channel is bounded 

 above by a much warmer (8°-10°) and Salter (35%o+) bottom zone, 

 from 100 to 300 meters thick, (Fig. 8, 9, 14; 26, 27, 32), just such as 

 characterizes corresponding profiles west and south of Cape Cod 

 (1915). And this could not have been the case, had upwelling been 

 taking place up the slope. Off Shelburne, too, the abyssal water 

 was separated from the even colder Cabot Current by a warmer 

 bottom zone (5°-8°) between 120 and 400 meters, both in 1914 and 

 in 1915 (Fig. 11, 73), though the zone of high salinity did not reappear 

 there. In short, there is no reason to suppose that abyssal water 

 wells up the slope, on to the continental shelf, anywhere between 

 southern Xova Scotia and Chesapeake Bay, in summer.^ Nor do 

 the winter temperatures and salinities of the Gulf afford any more 

 evidence of the presence of abyssal water there at that season. 



Tidal currents are so strong in the Gulf as to obscure the dominant 

 circulation during most of the year (1914a, p. 83). But salinities, 

 particularly the salt tongue in the east (p. 196), and plankton (p. 246) 

 combined, suggest that the main axis of the eddy-like drift which 

 occupies the Gulf is close to the land, which it follows, from east to 

 north and west, sometimes with seaward expansions off Penobscot 

 Bay and Cape Ann, the direct product of river freshets (1914a, 1915, 

 pi. 2). 



It is obvious that there must be a considerable outflow from the 

 inshore part of the Gulf, to offset the great amount of river water, 

 (p. 239), besides the increments of offshore and of Cabot Current 

 water, which enter it. Our earlier work suggests that the overflow 

 takes place chiefly along the west side, past Cape Cod; though with 

 no definite current there, but rather a gradual fan-like drift through 

 the South Channel, to Nantucket Shoals, and Georges Bank. But 

 this process is not wholly restricted to the west side of the Gulf, the 

 cool fresh band (Fig. 8), which was encountered on the eastern end 



' Account is only taken here of the upper zone of the slope, above the 500 meter-level, i. e., 

 of upwelling which might affect the coast water. 



