248 bulletin: museltm of comparative zoology. 



3° warmer at 100 fathoms in 1913 than in 1912 (Stations 10088, 10007) . 

 The higher temperature in the upper layers in 1913 was probably due 

 to the fact that the observations were made a month later than in 1912. 

 But this will not account for the difference at fifty fathoms and below. 



Off Cape Cod the 1912 temperatures were 3.5° lower on the surface, 

 3°-7° higher in the mid-depths, than those of 1913. But this is the 

 type of difference which might be expected from the advance of the 

 season (the 1912 Station, 10043, was three weeks later than that of 

 1913), being the first step in the equalization of temperature which is 

 complete, down to forty fathoms, by November (1914b). And I 

 doubt whether there was any more temperature difference between the 

 Cape Cod waters of 1912 and 1913 than can be explained on this 

 ground. 



Off Piatt's Bank the stations for the two years were made at so 

 nearly the same season (August 7, 1912 and August 10, 1913) that no 

 seasonal difference need be allowed for. The upper thirty-five fathoms 

 proved to be almost exactly the same in 1913 as in 1912, except for 

 the immediate surface, which was 2° colder, a difference which may 

 be due to the fact that in 1912 (Station 10023) the temperature was 

 taken in the afternoon of a very warm and calm day; in 1913, at 

 daybreak. But below thirty-five fathoms, the water was about 1° 

 warmer in 1913. 



Our stations of 1913 in the eastern basin were made at almost the 

 same localities, and within a few days of the dates of those of the year 

 before. On its western side the water was warmer down to ten 

 fathoms in 1913 than in 1912; but the difference was so slight that it 

 is a question whether it is anything more than evidence of diurnal 

 warming, one station having been occupied in the daytime, the other 

 at night. And the two were almost precisely alike below eighty 

 fathoms. But the temperatures of 1913 are 2-3° colder in the mid- 

 layers. The east side of the basin was warmer in 1913 than in 1912, 

 down to thirty-five fathoms, the greatest difference being almost 

 4° at twenty fathoms. But below that level it was 3° colder all 

 the way down to the bottom. And this is also true of its northern 

 end (Stations 10097, 10026), the extreme variation being 2°, at 100 

 fathoms. 



The range of salinity on the surface was smaller in 1913 (31.8%o- 

 32.8%o) than in 1912 (31.06%o-32.84%o) ; but this is probably chiefly 

 due to the fact that in 1913 most of our work was carried on in August, 

 by which time the salinity of the coast water may be expected to be 

 higher than a month earlier. But seasonal difference does not explain 



