728 
BULLETIN OF THE BUREAU OF FISHERIES 
have continued to drift westward past Cape Sable during this 4-week interval to 
maintain so almost 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 tributary 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 
Fig. 104.— Vertical distribution of salinity off Gloucester on March 1, 1920 (A, station 200501, and March 5, 
1921 (B, station 10511); for April 9, 1920 (C, station 20090); also for May 4 and August 31, 1915 (D, sta- 
tion 10266, and E, station 10306) 
it is probable that the value recorded for April 28, 1919 (about 31.7 per mille) ,fis 
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. 
