PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 941 
to state whether this creep involved the whole breadth at this depth or (which seems 
more likely) hugged its Browns Bank slope, as in the shoaler strata. 
In interpreting the dynamic contours in terms of potential drift at a depth at 
which the basin of the gulf is entirely inclosed except for one narrow channel, it is 
obvious that prime consideration must be given to the contour of the bottom, as this 
controls the possible movement of the water. When this is taken into account, the 
March chart (fig. 190) affords the best clue yet available to the movement of the 
slope water over the floor of the gulf at a season when this is entering in large volume 
via the trough of the Eastern Channel (p. 850). Dynamic contours for the 150-decibar 
Fig. 190. — Dynamic gradient, bottom to 150 decibars, referred to the southeastern side of the gulf as base station, for 
February and March, 1920. Contour lines for every dynamic centimeter 
level, like the distribution of temperature and of salinity, show this indraft following 
the eastern side of the basin inward, to eddy westward and so southward; but instead 
of completing a circuit around the cyclonic center (“low” on the chart— fig. 190), 
the drift will obviously be deflected by the slope of Georges Bank. The angle at 
which the contour (or stream) lines strike the latter suggests an overflow into the 
dead western side of the basin. It is here, then, as well as along the northern 
slopes of the gulf, that the consumption of this slope water chiefly takes place dur- 
ing the early spring, as tides and wind currents constantly mix it with the less saline 
but colder stratum above. 
