208 



bulletin: museum of comparative zoology. 



part of the Gulf as a whole. Thus both in the trough north of Cape 

 Ann (Fig. 43), and over the Western Basin (Fig. 45, 46), the same rapid 

 warming of the surface takes place during the spring and early sum- 

 mer, culminating in August; after which the water cools once more. 

 And in the trough seasonal warming is appreciable down to 150 

 meters, just as it is off Cape Ann (Fig. 41). But in the deep Western 

 Basin very little seasonal change took place with the advance of the 

 season, in 1915, below 100 meters, which was the level of minimum 

 temperature (p. 215). The temperature of the eastern half of the 



April May June July Aug. Sept. Oct. April May June July Aug. Sept.Qct. 



Fig. 43. Fig. 44. 



Fig. 43. — April \a October temperatures at the surface, 25, 50, 100 and 150 meters, 

 in the trough north of Cape Ann, for 1913-1915 (Stations 10278, 10325). 

 The dotted curves are for 1913 (1914b, p. 393). 

 Fig. 44. — April to October salinity at the surface, 50, 100 and 150 meters, in the 

 trough north of Cape Ann for 1913-1915 (Stations 10278, 10325). 

 The dott«d curves are for 1913 (1914b). 



Gulfi likewise rose, from May onward, as might have been expected. 

 Butithe seasonal range of surface temperature is smaller there than 

 in the west, (4°-20° in the western, 3°-13° in the Eastern Basin); and 

 its maximum reached later in the season (Fig. 49, 51, 52). Thus 

 summer warming results in a great increase in the vertical range of 

 temperature, from spring to mid-summer, over the whole Gulf, except 

 at localities, such as German Bank and the Grand Manan Channel, 

 where the water is kept thoroughly mixed b}- strong tidal currents. 



