232 bulletin: museum of compakative zoology. 



The surface salinit\^ on the other hand, was as a whole slightly 

 higher in 1913 than in 1914, with a maximum difference of .S%o off 

 Cape Ann, .6%o in the "Western Basin, while the salt tongue which 

 characterized the east side of the Gulf in 1913, (1915, p. 203, pi. 2), 

 was not evident on the surface in 1914, though it was in the deeper 

 layers (p. 196). 



Taking seasonal differences into account, temperature and salinity 

 were about the same on the surface in 1915 as the year before, the 

 fact that the surface was considerably salter over the western 

 basin in 1915 than in 1914 [Stations 10254 and 10255, 1914; surface 

 salinity 31.55%o and 31.89%o: Stations 10308 and 10307, 1915; 

 surface salinity 32.47%o and 32. 52%^] while on German Bank and off 

 Shelburne the reverse was true, being probably due to the difference 

 in season between the two sets of observations; 1915 and 1914 

 agree in the main with 1913 in the vertical distribution of salinity 

 and temperature, especially in the fact that the water of the central 

 and western parts of the Gulf was coldest at about 100 meters, warmer 

 below, instead of uniform in temperature from about 100 meters 

 down to the bottom as in 1912 (1914a). But as a whole this vertical 

 warming of the deeper layers was more pronounced in 1914 than either 

 in 1913 or in 1915, as appears in the following summary of temperatures 

 and salinities at corresponding localities from summer to summer.^ 



Off Cape Ann the salinity was lower at all depths in 1914 and 1915, 

 which were almost exactly alike, than in 1912 or 1913, the differences 

 between 1914 and 1912, which was the fresher of the two previous 

 years, being A-.b%o- I^ut the greatest temperature difference be- 

 tween the three years, at any level below 20 meters, was less than 1°. 



Except for the immediate surface, so subject to seasonal change, 

 the Western Basin was warmer down to 100 meters in 1915 than in 

 any previous year of record; below that depth the temperatures for 

 1915 are, as a whole fractionally cooler than those for either 1913 or 

 1914, warmer than 1912; though with an extreme variation of only 

 about 2.4°. In 1913, 1914, and 1915 the water was coldest at about 

 100 meters (p. 167); in 1912 the temperature was uniform from 120 

 meters down to the bottom. Salinity here was about the same in 1913 

 as in 1912 (1915, p. 204); from .66%o to A2%q lower in the upper 

 layers in 1914 than in 1912 or 1913 (1915, p. 204); with 1915 slightly 

 the saltest year of the four down to 40 meters (a difference probably 

 seasonal); below 200 meters salinity was about the same in all four 

 years. 



' See tables p. 333. 



