734 



BULLETIN OF THE BUBEAU OF FISHERIES 



An interesting change did take place, however, at the 40-meter level in the east- 

 ern side of the gulf from March to April in 1920, the pool of saltest (33 per mille) 

 water (p. 70S) having drifted northward, so to speak, from the ofEng of German Bank 

 to the offing of Lurcher Shoal, but having been cut off, at the same time, from the 

 still more saline water outside the edge of the continent by a considerable decrease 

 in the salinity of the southeastern part of the basin and of the Eastern Channel (cf . 

 fig. 115 with fig. 93) . This change, however, did not result from an expansion of the 



FIG. 112.— Vertical distribution of salinity in the western arm of the basin of the gulf off Cape Ann. A, March 24, 1920 

 (station 20087); B, April 18, 1920 (station 2nil.5); C, May 5, 1915 (station 10237); D, Juna 25, 1915 (station 10299); B, 

 August 22, 1914 (station 10254) 



cold Nova Scotian water iu this direction because accompanied by an increase in 

 temperature. 



The most obvious effect of the increase that takes place in the salinity of the deeper 

 levels of the gulf during the spring is to carry the isohalines for successive values west- 

 ward, until the entire basin at the 100-meter level was made more salme than 32.6 

 per mille by mid-April in 1920, and most of its area more saline than 33 per mille 

 (cf. fig. UG with fig. 94). As a result, the west-east gradation in salinity decreased, 

 and at the same time water more saline than 33 per mille flooded in toward the 



