PHYSICAL OCEANOGRAPHY OF THE GUU' OF MAINE 745 



The most instructive feature of the May chart in the eastern side of the gulf is 

 the similar expansion of surface water less saline than 32 per mille westward over 

 the basin from the offing of Cape Sable, which owes its low salinity to the Nova 

 Scotian drift from the eastward. 



The critical isohaline (32 per mille) bounding this tongue had been carried about 

 as far west into the gulf as this at least a week earlier in the spring of 1919, with 

 actual values almost precisely the same.*' Consequently, the picture presented on 

 the surface chart for May (fig. 120) may be taken as typical of the season when the 

 flow into the gulf past Cape Sable is at its maximum, irrespective of the precise 

 date when this falls. 



The lack of data on the salinity of the southeastern part of the Gulf of Maine 

 for May is a serious gap, for without such it is impossible to tell how far the fresh- 

 ening effect of the Nova Scotian water extends toward Georges Bank, or over the 

 latter, when it is at its maximum. However, it is certain that water of low salinity 

 from this eastern source did not reach the southwestern part of the bank at any 

 time prior to the 17th of May in 1920, whatever may have happened later that spring, 

 because no appreciable alteration took place in the salinity of the surface, which 

 was about the same there on that date (station 20129) as it had been on February 

 22 (station 20045). 



We also await observations on the salinity of the shoal water along the west 

 coast of Nova Scotia for May, to show how low it is reduced there by vernal fresh- 

 ening from local sources. It is not likely, however, that the eastern margin of the 

 open Gulf of Maine ever falls below 30 per mille in salinity, unless right at the mouth 

 of some stream, because no large rivers open along this part of the coast, because the 

 outflow from the Bay of Fundy is directed westward (p. 916), and because there is 

 no reason to suppose that the Nova Scotian current ever brings water less saline 

 than about 30.8 to 31.5 per mille past Cape Sable.*' 



It is a question of moment in the natural economy of the gulf whether and to what 

 extent the water of the Nova Scotian current turns northward after it has passed 

 Cape Sable. This the reader will find discussed in another chapter (p. 680). I need 

 remark here only that the surface salinities for May, 1915, and especially the course 

 of the isohaline for 32 per mille (fig. 120), mark a westward drift toward the center 

 of the gulf; but considerably lower salinities off the mouth of the Bay of Fundy in 

 May, 1915, than in April, 1920, suggests some movement of water in that direction 

 also, from the cape, as characteristic of this season. 



The vernal freshening of the coastal belt of the gulf by land water, and of the 

 eastern side by the Nova Scotian current, are annual events, though differing from 

 year to year in their time schedule as well as in the magnitude of the alterations 

 they cause. A considerable divergence from year to year has been recorded in May 

 in the west-central part of the gulf, which neither of these sources of low salinity 

 appreciably affects up to that season. If the early May state of this part of the 

 gulf in 1915 (fig. 120) be the regular seasonal sequence to the AprU state, as repre- 

 sented by 1920 (fig. 101), a considerable salting of the superficial water layer is to be 



s' Surface salinity 31.98 per mille at Ice Patrol station 21; 31.71 per mille at Ice Patrol station 22 on German Bank. 

 6' Neither the Ice Patrol nor the Canadian Fisheries Expedition have reported salinities lower than 30.8 per mille along the 

 outer coast of Nova Scotia in April or May. 



