922 
BULLETIN OF THE BUREAU OF FISHERIES 
component of the eddy had shifted southward to skirt the northern slopes of 
Georges Bank more closely. 
Information as to the movement of water along the bottom of the Northern 
Channel is much to be desired at the season when the Nova Scotian current is flood- 
ing in greatest volume into the gulf. Some drift may be assumed to take place into 
the gulf by this route as deep as 100 meters in 1915, to account for the concen- 
tration of the most saline water in the western side of the basin at the 100-meter 
level in May (fig. 127), instead of in the eastern side, as at other times of year. 
It is probable, therefore, that when the drift past Cape Sable is at its maximum it 
causes a westerly shift in the vortex of the general eddy in the mid depths, though 
not essentially altering the anticlockwise type of circulation, however. Any west- 
erly drift that may have taken place along the bottom of the Northern Channel in 
1915 had ceased by June; on this basis, alone, is the abrupt east-west transi- 
tion that appears there on the 100-meter chart of temperature for that month expli- 
cable (fig. 43). 
In midsummer the transition from lower salinities and temperatures in the 
western side of the gulf to higher in the eastern, at the 100-meter level, and the 
sweep of the successive isohalines and isotherms from east to west along the northern 
slope of the gulf, again give evidence of a general set northerly past Nova Scotia 
and westerly along the coast of Maine in the mid depths, paralleling the dominant 
circulation at the surface. The nontidal movement of water of the southern side of the 
basin at this level is not so clear, the picture being confused by an area of relatively 
high salinity and temperature off the northern slope of Georges Bank near the 
entrance to the Eastern Channel, which is not easy to account for. 
In spite of this and of other apparent anomalies the distribution of temperature 
and salinity in the mid depths, as exemplified by the 100-meter level, are, as a whole, 
compatible with the domination of the basin by the general Gulf of Maine eddy, 
anticlockwise in character. 
The horizontal circulation of the gulf at greater and greater depths is more and 
more directed by the contour of the bottom, which gives the basin the outlines of a Y, 
with two arms uniting and open to the Eastern Channel (p.784) at 175 meters, but 
entirely inclosed at 200 meters and deeper. 
With temperatures and salinities recorded at one deep station or another for so 
many months and years, it can be stated confidently that the movement of bottom 
water inward into the gulf takes place in pulses, the secular fluctuations of which 
have only been glimpsed as yet (p. 850). On the other hand, dynamics (fig. 204) and 
the distribution of temperature and salinity point to some outgoing drift via the 
western (Georges Bank) side of the Eastern Channel between these pulses in 
summer (pp. 789, 852). 
The presence of water of high salinity (34 per mille) in both arms of the trough 
but never (so far as yet recorded) over the submarine ridge that separates them is 
good evidence that the latter divides the slope water as it drifts inward in the deep- 
est stratum of the gulf. 
Two separate anticlockwise eddying drifts are indicated in the bottoms of the 
two arms of the trough, at depths of 175 meters and deeper, by salinities and tem- 
peratures averaging somewhat higher on the side that would be to the right, for an 
