806 BULLETIN OF THE BUREAU OF FISHERIES 



basins, whether off Cape Ann (station 10490) or oflF Cape Cod (station 10491) ; more 

 saline, too, than at a neighboring location at any time during the winter of 1912-13. 

 If these determinations were correct, ' they mean that bottom water had been well- 

 ing up into the bowl from greater depths in the basin at some time shortly previous. 

 However, this movement had then ceased, and the inequalities in salinity were 

 decreasing; otherwise the temperature would have been about the same at the sur- 

 face as in the deeper layers (6.9° to 7°), instead of more than 1° lower (5.56° at 

 station 10489). It is certain, also, that the unexpectedly high salinity did not 

 persist long at this locality, for the whole column of water had freshened to 32.6 to 

 32.7 per mille there by the 5th of the following March (station 10511).'° 



Nor did any upwelling that may have taken place off the mouth of Massachu- 

 setts Bay in December, 1920, involve the inner parts, for the whole column of water 

 proved decidedly less saline off Boston Harbor on the 29th (station 10488) than at 

 the mouth of the bay (station 10489); less saline, too, than near Gloucester on 

 January 30, 1913 (station 10051), when salinity ranged from 32.56 per mille at the 

 surface to 32.8 per mille on bottom. 



During this midwinter the salinity of the superficial stratum of water was lowest 

 (31 to 32 per mille) along the shore between Cape Ann and Cape Elizabeth, on one 

 side of the gulf, and next the west coast of Nova Scotia, on the other, with a mini- 

 mum of 30.02 per mille a few miles south of the mouth of the Merrimac River, no 

 doubt reflecting the freshening effect of the latter, but slightly higher along the 

 northern shore of the gulf (32.3 to 32.6 per mille) and in Massachusetts Bay (32.1 

 to 32.5 per mUle) . This regional distribution was paralleled at 40 meters (though 

 with actual values averaging about 0.3 per mille higher), except that the minimum 

 for this level was close to the Nova Scotian coast (31.3 per mille) instead of off the 

 Merrimac River, proving the freshening effect of the latter to have been confined to 

 the uppermost stratum of water at the time. 



The narrow confines of water less saline than 32 per mille in midwinter, and 

 the rather abrupt transition in the western side of tlie gulf to considerably higher 

 values a few miles out at sea, contrasted with the much more extensive area inclosed 

 by that isohaline in April and in May (figs. 101 and 120), reflect the fact that the 

 rivers discharge much less water into the gulf in late autumn and early winter than 

 they do in spring. 



During the winter of 1912-13 the vertical stratification of the water at the 

 mouth of Massachusetts Bay, characteristic of the summer season, gave place to a 

 close approach to vertical homogeneity in salinity, as well as in temperature, by the 

 middle of December, and so continued through the winter. Closer in to the shore, 

 however, on both sides of Cape Ann, a greater vertical range of salinity persists into 

 January and probably right through until spring." In 1920-21 all the stations 

 showed a vertical range of more than 0.3 per mille salinity in the upper 100 meters, 

 except off Yarmouth, Nova Scotia, and off Cape Cod (stations 10501 and 10491), 

 where the water was virtually homogeneous, surface to bottom, and near Seguin 



» There is no technical reason to doubt their accuracy. 



"> In 1913 the salinity at a near-by locality continued to increase until Mar. 19, when it attained its maximum of 33 per 

 mille at the surface and 33.17 per mille on bottom at a depth of 88 meters. 



» Vertical range of 0.3 to 0.7 per mille in depths of 30 to 35 meters at stations 10051 and 10052 on Jan. 30, 1913. 



