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bulletin: museum of comparative zoology. 



But this vertical inequality is again obliterated during the autumn 

 in the eastern, just as it is in the western part of the Gulf (1914b). 



Even apart from such disturbing elements as vertical circulation 

 caused by local currents, the seasonal range of salinity is less uniform 

 over the Gulf than is that of temperature. To begin with, the sea- 

 sonal variation is much smaller in the deep basin than near land, as 



JVlay June July Aug. Sept. 



Fig. 46. 



Fig. 47. 



Fig. 46. — Temperature at the surface, 50, 100 and 200 meters, in the Western 



Basin, May-September, 1915. 

 Fig. 47. — Salinity at the surface, 50, 100 and 200 meters, in the Western Basin, 



May-September, 1915. 



might be expected in view of the influence of river water (p. 239; 

 1914a, 1915). Thus over the Western Basin the surface salinity 

 changed only by about .7%o (Fig. 45, 47) from May to September, as 

 against a range of nearly 2.%o off Cape Ann (Fig. 42) ; though the 

 surface was at its minimum at about the same season. And there was 

 practically no seasonal change in the mid-depths of the Western Basin; 

 a statement likewise true of the bottom water from May to June. The 

 latter, however, showed a decided rise in salinity from June to Sep- 

 tember. Similarly, the range of salinity in the Eastern Basin, in the 



