728 



BULLETIN OF THE BUREAU OF FISHERIES 



have continued to drift westward past Cape Sable during this 4-week interval to 

 maintain so ahnost uniformly low a salinity (31.7 per mille) so far westward. 



The data for 1919 and 1920 thus show a considerable yearly variation in the date 

 when the Nova Scotian current most influences the salinity of the Gulf of Maine — a 

 variation associated with the factors that govern the general scheme of circulation 

 along the Nova Scotian shelf to the eastward, and with the outflow from the Gulf 

 of St. Lawrence (p. 830). Therefore, it does not necessarily follow that if the gulf is 

 early or late in showing the freshening effects of the freshets from its tributaiy rivers 

 in any given year the cycle of salinity will be correspondingly early or late in its 

 eastern side. 



The lowest value to which Nova Scotian water may reduce the salinity of the 

 surface of the eastern side of the gulf can not yet be stated; but on theoretic grounds 



31 

 Metsr 



10 

 20 

 30 

 40 

 50 

 60 

 70 

 80 

 90 

 100 



no 



120 

 130 

 140 

 150 

 160 



.2 .3 

 O 



.8 .9 32 



Fig. 104.— Vertical distribution of salinity off Gloucester on March 1, 1920 (A, station 200501, and March 6, 

 1921 (B, station 10511); for April 9, 1920 (C, station 20090); also for May 1 and August 31, 1913 (D, sta- 

 tion 10266, and E, station 10306) 



it is probable that the value recorded for April 28, 1919 (about 31.7 per mille), is 

 near the minimum, because any flow into the gulf from the eastward necessarily 

 crosses the coastwise bank off Cape Sable, where tidal churning is so active that the 

 fresher current must constantly mix with Salter water and so, to a considerable extent, 

 lose its distinguishing character. 



VERTICAL DISTRIBUTION OF SALINITY IN APRIL 



Graphs for successive dates in the spring of 1920 (figs. 104 to 109, 112-114) illus- 

 trate the effect that the vernal outpouring from the rivers exerts on the deeper strata 

 next the land during the last weeks of March and first half of April. 



