PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 
913 
is along the outer part of the shelf, not transverse to it, though with some tendency 
indicated toward an eddying movement northward toward the land to the west 
of Nantucket Shoals. All this, again, is at once reconcilable with the drifts of bot- 
tles set out in this side of the gulf, especially with the tracks eddying westward out 
of the gulf past Nantucket Shoals, and with the group that went west from the edge 
of the continent abreast of Cape Cod (series B, outer end, p. 882). 
The failure of any evidence, by salinity, of a surface drift from the continental 
edge out into the ocean basin in the region, in any summer of record, is corroborated 
by the fact that from the outer end of line B (fig. 174) only four bottles are known 
to have reached the general North Atlantic drift, and so to have gone across, one to 
England, one to Ireland, the other to the Canary Islands and the Azores. 
The distribution of salinity at a depth of 40 meters has proved extremely diag- 
nostic of the dominant circulation of the gulf, even more so than at the surface, the 
chart for July and August, 1914 (fig. 145), being the most instructive because cover- 
ing the area as a whole. Its most noticeable feature — a continuous tongue of water 
of high salinity (33 to 33.4 per mille), extending from the Eastern Channel and 
Browns Bank inward to the north along the eastern side of the basin as far as the 
mouth of the Bay of Fundy — obviously reflects an unmistakable set of water into 
the gulf from the edge of the continent. The surface charts, the reader will recall, show 
nothing , of this sort, evidence that the inward current (the existence of which is 
proven by several lines of evidence) did not involve the superficial stratum. Neither 
does it draw direct from the oceanic water (which would swing the isohalines for 34 
to 35 per mille into the Eastern Channel), but from the mixture that takes place 
between tropic water and the water of the banks along the edge of the continent 
abreast of the gulf (p. 842). So far as the contour of the bottom is concerned, the 
whole southern aspect of the gulf, from Nantucket Shoals to the vicinity of Cape 
Sable, is open to overflows from this same source down to a depth of 40 meters. 82 
Actually, however, we have found no evidence, in salinity, of any indraft of this 
sort anywhere to the westward of the Eastern Channel. 
The expansion of the isohalines for 33 and 32.9 per mille to the westward along 
the coast of Maine, and the course of the isohaline for 32.5 per mille on the 40- 
meter chart just mentioned (fig. 145), combined with the location of the saltest 
tongue close against the eastern slope of the basin, are most readily reconcilable with 
a dominant set northward in the eastern side of the gulf (complicated by the evi- 
dences of upwelling in the offing of the Bay of Fundy already mentioned on p. 768), 
veering westward along the coast of Maine, and so southward around the periphery 
of the gulf, finally to turn southeastward as it is directed toward Georges Bank by 
the slopes of Nantucket Shoals. 
This essentially reproduces the anticlockwise eddy indicated by the distribution 
of salinity at the surface (p. 911) as well as by the bottle drifts (p. 906), but the fact 
that the highest salinities at 40 meters lie 10 to 20 miles out from the 40-meter 
contour line in the eastern side of the gulf, not close in against the latter, is evidence 
that the eastern side of the eddy lay farther and farther out from the Nova Scotian 
11 Except for the shoals on Georges Bank. 
