78 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
condition in all ocean waters during the warm season, though there 
are temporal and local inversions due to temperature conditions in 
winter (Helland-Hansen and Nansen, 1909). But the rate of increase 
varies greatly in different regions, there being two very different types 
of vertical distribution in the Gulf. The first, exemplified over 
Jeffrey’s and German Bank, and in the Grand Manan Channel, 
Station 25 (fig. 34), Station 29 (fig. 34), Station 35 (fig. 36), shows 
only a very slight increase from surface to bottom; but in the second, 
comprising practically all the other stations, there is a large rise, with 
slowly decreasing rate from the surface downward. The curves for 
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the last recall the salinity curves at corresponding stations; but the 
difference between surface and bottom was in every case considerably 
greater in the former than in the latter, at corresponding stations. 
The most important conclusion to be drawn from the density curves 
is that over the whole deep basin, in Massachusetts Bay, and along 
the coast from Cape Ann to the Penobscot, the water was in very 
stable vertical equilibrium during July and August; but that on 
Jeffrey’s and German Banks and in the Grand Manan Channel the 
difference in density in different depths was so slight that it would 
offer very little resistance to vertical circulation. In comparing the 
ened al 
