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 water 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. Lawrence 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 réles, now one, NOW 
another having the upper hand with the succession of the seasons; 
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