PHYSICAL OCEANOGKAPHY OP THE GULP OF MAINE 837 



the case, for were Georges and Browns Banks subject to frequent overflows by the 

 high temperatures of the so-called "Gulf Stream" sufficient in amount to dominate 

 the column from surface to bottom, existence on the Banks would become impos- 

 sible for cod, haddock, halibut, and, in fact, for the whole category of boreal fishes. 



Under exceptional conditions departures from the normal temperatures and 

 salinities along the zone of contact of the banks and tropic waters may allow the 

 latter to reach the Gulf of Maine as a surface drift if driven by southerly winds. 

 An overflow of this sort was, in fact, reported by Capt. E. Kinney of the S. S. 

 Prince Arthur, who observed unusually blue water with gulf weed and a tempera- 

 ture of 20° C. (68° F.) in the center of the gulf, latitude 42° 43' N., longitude 69° 

 13' W., on July 14, 1911, preceded for several days by a strong current toward the 

 northwest in its western side (U. S. Hydrographic Office pilot chart for January, 

 1913). However, no events of this sort have come under our observation, so they 

 must be exceptional, for their effects on the salinity of the gulf and on its plankton 

 would be unmistakable. 



It may be definitely asserted, therefore, that tropic water from outside the con- 

 tinental edge seldom affects the temperature or salinity of the gulf except as one of 

 the constituents of the water that fiows in through the Eastern Channel. 



It is one of the most interesting oceanographic features of the Gulf of Maine 

 that the latter is so little subject to tropic influences, either in the physical character 

 of its waters or in its fauna or flora, when tropic water lies so close at hand. 



COASTAL WATER FROM THE WEST 



The possibility that the coastal water overflows around Cape Cod from the 

 west in any considerable volume, and so into the Gulf of Maine, seems extremely 

 remote. On the contrary, all the evidence of current-meter measurements, drift- 

 bottle experiments, distribution of temperatures and salinities (see especially p. 974), 

 and geographic distribution of the fauna (bottom as well as planktonic) points to 

 just the reverse movement — i. e., out of the gulf in this side. The evidence that the 

 dominant drift past Cape Cod, and so around or over Nantucket Shoals, is out of 

 the Gulf of Maine, not into the latter, is conclusive. 



RIVER WATER 



In addition to the superficial ocean currents just discussed, which bring water 

 to the Gulf of Maine, its tributary rivers discharge a volume of fresh water so large 

 that it must be taken into consideration in any study of the salinity or circulation 

 of the gulf. 



Unfortunately, the annual combined discharge of the several river systems can 

 not yet be stated, much less the contribution made by the numerous minor streams 

 that empty into the gulf, for most of the fiow measurements made by the United 

 States Geological Survey within recent years (see especially Porter, 1899; Pressey, 

 1902; and Barrows, 1907 and 1907a) have been for localities far upstream. The 

 published data for the Kennebec at Waterville, Ale., and for the Merrimac at 

 Lawrence, Mass., are perhaps the most instructive in the present connection. These 

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