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bulletin: museum of COMPARAXn^E 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 Xansen, 1909). But the rate of increase 

 varies greatly in different regions, there being two very different tx'pes 

 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 



Fig. 35. — Curves of density in situ at Stations 2. 11. 26. 



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 IManan Channel the 

 difference in density in different depths was so slight that it wouldF 

 offer very little resistance to vertical circulation. In comparing the 



