PHYSICAL OOEANOGKAPHY OF THE GULF OF MAINE 957 



was then lighter still (i. e., the surface potentially still higher) all along the coast 

 westward from Mount Desert, where no observations were taken that summer. 



Only in one small region did the dynamic contours for that July prove non- 

 conformable to those of August — namely, in the immediate offing of Cape Sable. 

 Here a slope rising from Browns Bank across the Northern Channel gave place to a 

 potential dip next the cape in July, reflecting the high density of the cold water 

 next the Nova Scotian coast reminiscent of the Nova Scotian current of a month or 

 two earlier. Consequently, while the surface water over the Northern Channel was 

 then drifting toward the gulf, that next the cape was drifting away from it; but the 

 rising temperature of the next three weeks (combined with considerable freshening) so 

 decreased the density of this relict water that by mid August a rising slope was 

 recorded from German Bank in toward the cape, corresponding to the northerly 

 drift toward the Bay of Fundy with which so many drift bottles have journeyed. 

 Observations taken near Yarmouth, Nova Scotia, by Vachon (1918) in September, 

 1916, make it probable that in summer this sector of the coast line is normally 

 fringed by water relatively lighter than is shown on the chart for 1914 (fig. 200). 



The distribution of density in the Bay of Fundy in summer has been studied by 

 Mavor (1923). Here the lightest water Ues along the northern side in the upper 60 

 to 80 meters, the heaviest bottom water banking up in the central part of the basin in 

 depths greater than about 100 meters. This type of distribution, as Mavor (1923, 

 p. 364) makes clear, must tend to develop a surface drift from east to west toward 

 the mouth of the bay along the New Brunswick shore. The "rising of the cold 

 (below 7°) and salt (above 33 per mille) water in the middle of the section" indicates, 

 as he remarks, an anticlockwise rotation of the bottom water guided by the contour 

 of the slopes, which is consistent with the bottle drifts (p. 868). 



So long as the dynamic contour of the surface of the gulf is of the general type 

 shown on Figure 203, a generally anticlockwise type of circulation will tend to domi- 

 nate the whole basin, centering some 40 to 60 miles offshore in the offing of Mount 

 Desert Island, with a subsidiary eddy, likewise anticlockwise, involving the Bay of 

 Fundy. The contour Unes show that a southwesterly drift is then to be expected off 

 Mount Desert Island and past Penobscot Bay, but one constantly tending offshore, 

 veering rather abruptly southward and southeastward in the offing of Casco Bay and 

 so out across the basin. 



Off Cape Ann, too, the dynamic drift tended to the southeast in August, 1914; 

 but a division was indicated there, with the coastal water recurving toward Cape Cod. 



Comparison with the bottle tracks makes it evident that dynamic circulation of 

 this type corresponds very closely to the drifts of the bottles set out off Mount 

 Desert, as these have veered from southwest through south and east and so north- 

 ward along the Nova Scotian coast (figs. 183 and 184). The center of this eddy 

 movement, however, seems to have been situated a few miles farther south and west 

 in 1923 than the dynamic chart (fig. 203) shows it for 1914. 



These dynamic contours also correspond to the southeasterly component of the 

 tracks of bottles set out off Cape Elizabeth (figs. 180 to 182) and with the fact that 

 most of these turned offshore from the beginning and did not parallel the coast line 

 southward toward Cape Ann, as happens earlier in the season. 

 37755—27 29 



