262 bulletin: museum of comparative zoology. 



In short, the Gulf of Maine is warmed, not cooled, by the combination 

 of northern and Gulf Stream water which enters it; and this is even 

 more true of the coastal waters south and west of Cape Cod. This 

 does not mean that more or less northern water does not enter into 

 the composition of the coast water; on the contrary, such water 

 enters into the Gulf of Maine in amounts varying from year to year. 

 But by the time it has flowed so far south as this, it has been so 

 warmed by mixing with warm off shore water, that it is no longer cold 

 enough to chill the coast w^ater below the temperature which would 

 be given it by the land climate alone. And the northern water has 

 even less effect on salinity than on temperature south of Nova Scotia, 

 because the volume of fresh water which empties into the Gulf of 

 Maine, and over the shelf beyond Cape Cod, is sufficient to lower the 

 salinity of the coast water nearly to that of the water which flows 

 out of Cabot Strait (p. 259). 



The upper layers of the Gulf Stream can not be neglected in study- 

 ing coast waters. It has long been known that Gulf Stream water 

 drifts northward almost every summer, flooding the surface even to the 

 southern shores of New England. And salinity profiles suggest that 

 it was a shoreward movement of the surface waters of the Stream, 

 dipping below the fresher coast water, which raised the salinity of the 

 bottom water of the shelf southwest of Nantucket so considerably 

 during July and August (p. 193). In the Gulf of Maine, too, Gulf 

 Stream water is probably of more importance than is usually realized, 

 its entrance being an annual phenomenon, signalized by the tropical 

 organisms it bears with it (p. 336) . 



The evidence marshalled in the preceding pages shows that our 

 coast water is not of any one origin; it does not even have any one 

 predominant source, as has been so often assumed, but is really very 

 complex and variable in its composition. The constituents which 

 enter into it are northern water, chiefly from the Gulf of St. Lawrence, 

 and hence itself coastal, not polar, plus a possible small component of 

 polar Labrador water; river water from the land; water of high 

 salinity from the upper layers of the Gulf Stream; water from the 

 mid-layers off shore, and possibly Atlantic abyssal water, besides rain 

 water. In just what proportions these components mix, is for more 

 detailed studies to show. But temperature and salinity suggest that 

 it is St. LawTence water which is the most important off Nova Scotia. 

 In the Gulf of Maine, St. Lawrence water, land water, and water from 

 the upper 100 fathoms off shore play more equal roles, now one, now 

 another having the upper hand with the succession of the seasons; 



