PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 967 
Thus, the wind then tends to act as a motive force for the southern and eastern 
sides of the Gulf of Maine eddy. 
It is obvious, however, that no matter how steadily the wind blew from the 
southwest it could not drive the entire surface of the gulf eastward unless the water 
were nearly enough homogeneous to allow a sinking current to develop in the eastern 
side, with the deeper stratum so fed flowing back from east to west, to well up again, 
in turn, in the western side. Circulation of this sort probably does take place 
to some extent along the Nova Scotian side of the gulf, in the Bay of Fundy, and 
along the coast of Maine east of Mount Desert, where active tidal currents keep 
the water so thoroughly stirred that it has little stability at most times of year. 
It is certain, also, that offshore winds do cause more or less upwelling along the 
western shore line, but the basin of the gulf as a whole, with its western and north- 
western margins, is so stable vertically that hydrostatic forces very strongly oppose 
any such “jibing,” as Sandstrom (1919) terms it. Consequently, any constant 
movement of the surface water northward toward the Bay of Fundy would tend to 
cause an “overflow” in the shape of a westerly drift along the coast of Maine — i. e., 
against the winds prevailing in summer. 
It is obvious that if the water be in stable equilibrium, southwesterly winds 
might or might not set a closed circulation of this type in motion, depending on 
their relative strengths and constancy in various parts of the gulf; depending, too, 
on the balance in various parts of the gulf between the Hydrostatic forces opposing 
jibing and the tendency of the wind to cause that process, as just explained. 
To value these several factors will require a knowledge of the gulf and of its winds 
much more intimate than can yet be claimed. It is certain that with winds reversed 
as often as they are over the gulf the balance varies constantly. However, the 
preceding analysis does make it clear, I think, that any eddying circulation which 
the southwesterly winds of summer might set up in the surface stratum of the gulf 
would shortly assume the anticlockwise character that, by evidence of more direct 
sorts, does actually dominate its basin. Consequently, the summer winds parallel 
the hydrostatic forces set in operation by regional inequalities of density in their 
general effects to this extent. On the other hand, the current flowing southward 
and out of the gulf past Nantucket Shoals, which forms part of the overflow from 
the gulf, is at right angles to the potential wind drift, hence holds its dominant set 
in spite of the prevailing wind. Neither can the wind be held responsible for the 
westerly drift of slope water along the continental edge in summer, because this 
current sets directly against the drift which the prevailing southwesterly winds 
would tend to produce there. 
The wind current, as it extends its effects deeper and deeper below the surface, 
will turn more and more to the right of the wind (losing, also, in velocity by 
geometric progression) ; also, with increasing depth the gulf becomes more and more 
nearly inclosed, so that any currents, however set in motion, are more and more 
directed by the contour of the bottom. 
The depth to which currents of wind origin do actually penetrate in the Gulf of 
Maine is therefore of immediate interest. Unfortunately, no mathematical method 
yet suggested can measure this, even approximately. However, it is certain that 
the stable state of the water of most parts of the gulf ordinarily confines wind 
