836 
BULLETIN OF THE BUKEAU OF FISHERIES 
finally northward toward the Gulf of Maine, via Browns Bank and the Cape Sable 
dead water. 
In years such as those just described the region in the offing of Cape Sable, 
out to Browns Bank, between the two major circulatory eddies (Scotian and Gulf 
of Maine) but not directly within the sweep of either, is evidently the site of a very 
active mixing of waters of diverse origins. Under such conditions a very abrupt 
east-west transition in temperature and salinity develops off the cape, proving that 
the westerly (inshore) component of the Scotian eddy is not the motive power for 
such water as does then flood into this side of the Gulf of Maine. This eddy, on 
the contrary, is clearly outlined by the surface salinity for July and August, 1914 
(Bigelow, 1917, fig. 18), and for June, 1915, as swinging offshore toward La Have 
Bank, which prevents it from flooding westward through the Northern Channel, 
toward which the rotation of the earth would direct it, did the contour of the bottom 
allow. 
The strong tidal currents off southern Nova Scotia must tend, however, to 
pump water from the Cape Sable deadwater into the gulf, because the flood, running 
westward at a mean velocit}^ of 1.4 knots (Dawson, 1908, station R; a journey of 
something like 8 % miles for any given particle of water), must follow westward and 
northward around Cape Sable as it is forced to the right against the shore by the 
effect of the earth’s rotation. With the ebb similarly deflected to the right, a clock- 
wise movement around the rounded outline of southwestern Nova Scotia naturally 
results, such as eddies around any submerged shoal in high northern latitudes. 
TROPIC WATER 
We may next consider the possibility that overflows of the surface stratum of 
tropical or “Gulf Stream” water, the inner edge of which always lies within a few 
miles of the edge of the continent, may enter the Gulf of Maine from time to time; 
also possible movements of the coast water from west to east past Cape Cod into 
the gulf, either via Vineyard Sound or around Nantucket Island. Water from either 
of these sources would reach the gulf as warm currents, contrasting with the cold 
Nova Scotian current, the former high in salinity, the latter low. 
As pointed out above (p. 700), events of the first category undoubtedly do occur 
on occasion. Small amounts of “Gulf Stream ” water have long been known to drift 
inward, toward the sector of coast line bounded on the east by Marthas Vineyard 
and on the west by Narragansett Bay, during most summers, bringing with them a 
typically tropical fauna of fishes, planktonic invertebrates, and Gulf weed (Sargassum) . 
Were it not for the peculiar distribution of densities off the slopes of Georges and 
Browns Banks, shortly to be described (p. 843), which produce more or less constant 
dynamic tendency for the surface stratum to move out, seaward, from the edge of 
the continent (a tendency altered into a long shore current to the westward by the 
deflective effect of the earth’s rotation; p. 846), tropic water might similarly be 
expected to drive in over the surface right across the banks under the propulsion of 
high and prolonged southerly winds. Under most conditions, however, the distri- 
bution of density imposes an impassible barrier to surface drifts from the southward 
into the gulf (p. 939). It is fortunate for the fisheries of New England that such is 
