756 BULLETIN OF THE BUREAU OF FISHERIES 



Scotia rose from 27.9 per mille on May 4, to 31.49 per mille on June 15 (Mavor, 1923, 

 p. 375) ; and some such succession may be expected close in to the mouth of any one 

 of the large rivers that drain into the gulf. 



No observations were taken in the western side of the gulf in June, 1915; but 

 the Fish Hatok stations for 1925 (figs. 129 and 130) show a similar increase of about 

 0.7 per mille in the surface salinity of Massachusetts Bay, from a mean of 31.57 per 

 mille on May 20 to 22 to a mean of 32.28 per mille on June 16 to 17, with no evi- 

 dence of the drift of water of low salinity into the bay from the north past Cape 

 Ann, which the isohaline for 31.5 per mille made apparant three weeks earlier 

 (fig. 119). 



Contrasting with the general rise in surface salinity that takes place alongshore 

 and over the eastern side of the basin from May to June, as just described, the charts 

 for 1915 (figs. 120 and 128) show a corresponding freshening of the surface over the 

 western side of the basin, resulting from the general dispersal of land water out to 

 sea combined with a cessation of the upwelling that was taking place there in May 

 (p. 746). In that particular year the actual decrease off Cape Ann was from 33 per 

 mille on May 5 (station 10267) to 32.5 per mille on June 26 (station 10299) — evi- 

 dence of the gradual tendency toward the equalization that follows the temporary 

 freshening or salting of any part of the gulf. 



I can say nothing of salinity over Georges Bank or for Nantucket Shoals in 

 June; data there for that month are desiderata. 



Although no notable alteration takes place in the vertical distribution of salinity 

 from May to June, the following minor changes are worth attention: 



The western branch of the basin, off Cape Ann (fig. 112), freshens notably from 

 the one month to the next in the upper 40 to 50 meters, but salts at depths greater 

 than 120 meters, resulting in a considerably wider range of salinity between surface 

 and bottom, a change important because of the greater vertical stability it gives to 

 the column of water as a whole. 



It is doubtful, however, whether any seasonal alteration of this order extends to 

 the southeastern part of the basin, because the salinity of the upper 50 to 60 meters 

 was almost precisely the same there on June 25, 1915 (station 10298), as it was 

 two months earlier in the season in 1920 (station 20112, April 12) ; and whUe the June 

 station was slightly the Salter of the pair at 100 meters, it was slightly the fresher 

 from 150 meters downward to the bottom. In the eastern side of the basin, too, 

 the vertical range of salinity decreases from May to June, instead of increasing, as 

 the Nova Scotian current slackens. The whole column of water over German Bank 

 was likewise (and for the same reason) about 0.2 per mille more saline on June 19 

 (station 10290, about 32.1 per mille) than it had been on May 7 (station 10271), 

 though as nearly homogeneous vertically, a condition maintained here the year 

 round by active tidal stirrings. 



In the Bay of Fundy, between Grand Manan and Nova Scotia, Mavor (1923, 

 p. 375) found much less spread between surface and bottom on June 15, 1917, than 

 on May 4, consequent on the considerable salting of the upper stratum just de- 

 scribed (p. 755) ; and the contrast between the moderately wide vertical range of salin- 

 ity there, as well as at our own station at the mouth of the bay on June 10, 1915 

 (station 10282), and the vertical homogeneity of the water of the Grand Manan 



