PHYSICAL OCEANOGBAPHY OP THE GULP OP 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 westv/ard 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 cori'oborated 

 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. ^^ 

 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 Hne 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 



»' Except for the shoals on Georges Bank. 



