234 bulletin: museum of comparative zoology. 



In a partially enclosed basin, subject to such violent climatic 

 changes as is the Gulf of Maine, and where waters of such different 

 temperatures and salinities struggle for the mastery, more or less 

 fluctuation in hydrography is to be expected from year to year. 

 But our data are now sufficient to show that such changes as do take 

 place are very small; and nothing has yet transpired to suggest that 

 they ever seriously affect the waters of the Gulf one way or the 

 other, as a biologic environment. That violent fluctuations may 

 occur at rare intervals, is of course possible; that they do so, along 

 the edge of the continental slope can not be disputed (1915, p. 265), 

 but we still await evidence of such events in the Gulf. 



Origin and Circulation of the Gulf of Maine Water. 



The explorations in 1912 (1914a) and 1913 (1915) showed that the 

 waters of the Gulf of Maine are complex, land water, Gulf Stream 

 water, and St. Lawrence water all taking part in their formation, 

 while the possibility that abyssal water might also enter, by up- 

 welling, into this complex has also been recognized. But the data 

 for those years was not sufficient to throw much light on the propor- 

 tions in which these different waters meet in the Gulf; or to disclose 

 the precise inflowing or outflowing currents, be;v'T)nd the fact that 

 there is an indraught on its east, and an outdraught on the west side 

 (1914a, p. 91; 1915, p. 231). The data for 1914 and 1915 advance 

 our knowledge of these questions, particularly as to the origin and 

 extent of the northern current. It is clear, indeed the early records 

 demonstrated, that the summer temperatures of the Gulf are not 

 much affected by cold northern currents, being nearly what would be 

 expected if it were an enclosed basin; the Gulf owes its low temper- 

 ature chiefly to the cold winter climate of the neighboring land mass. 

 But salinities, plankton, and the general set of the currents, show 

 beyond question, that a northern current does reach the eastern side 

 of the Gulf, though so mixed with Atlantic water that its hydro- 

 graphic influence is hardly appreciable; and some information is at 

 hand as to its seasonal variations. 



One of the first, and most important conclusions, drawn from our 

 early work was that the northern water on our coast is chiefly of 

 Gulf of St. Lawrence, not of Labrador Current origin; and as the 

 general theoretic reasons for this ^•iew are discussed elsewhere, 1915, 

 p. 251, Schott, 1897, Krummel, 1911), I need only point out here 

 how fully the records for 1914 and 1915 bear it out. 



Salinities (p. 182), temperatures (p. 174), and current records (p. 



