718 BULLETIN OF THE BUREAU OP FISHERIES 



that its deeper strata show almost no efifect of overflows from the deeps of the neigh- 

 boring basin. A profile running out from the Isles of Shoals would show a contrast 

 of this same sort, and due to the same cause, between the trough to the west of 

 Jeffreys Ledge (station 20061) and the basin to the east of it, though with the actual 

 difference in salinity not so great between the two sides of this rather steep ridge 

 because this particular trough is open to the north. 



The two phases of the salinity of the gulf that claim most attention in the first 

 days of spring, before the Nova Scotian current has spread westward past Cape 

 Sable, are the vernal freshening from the land, already mentioned (p. 704), and the 

 state of the water in the eastern side, where the inflowing bottom current is chiefly 

 concentrated. The latter is illustrated graphically in east-west profile (fig. 98) by 

 a very evident banking up of the saltest bottom water (salter than 33.5 per mille) 

 to within about 80 meters of the surface on the eastern slope of the gulf (station 

 20086), when it lay nearly 100 meters deeper in the western side of the profile 

 (station 20087, March 23), and by the contrast between its high salinity and the 

 considerably less saline masses of water on either hand. 



Unfortunately the three eastern stations (20084 to 20086) on this profile were 

 occupied about 3 weeks later, in date, than those immediately to the westward of 

 them, allowing the possibility that a cumulative development of the saline core 

 during the interval may have been partly responsible for the contrasting salinity. 

 But even if the most saline band was not as definitely limited on its western side, 

 at any given date, as it is represented, the profile certainly does not exaggerate the 

 gradation in salinity between the eastern and western sides of the basin, because 

 water samples were taken in both at the same date ( March 23 and 24, stations 

 20086 and 20087). A variation of at least 1 per mille in salinity is therefore to be 

 expected from west to east across the gulf at the 40 to 100 meter level during the 

 last week of March, but one decreasing with increasing depth from that stratum 

 downward to virtually nil in the bottom of the trough. It is also probable that 

 the whole western side of the basin remained decidedly uniform in salinity through- 

 out the month at any given level (p. 722). 



Had vernal freshening affected either end of this profile up to the date of obser- 

 vation (to March 24) , the surface would have been much less saline than the deeper 

 water at the inshore stations off Massachusetts, on the one side, or off Nova Scotia 

 on the other, just as was actually the case off the Kennebec Eiver on March 4 

 (p. 706, fig. 91). Instead of a distribution of this sort, however, the water at these 

 stations was nearly homogeneous in salinity from surface to bottom, evidence that 

 values somewhat lower there than in the basin merely represented the gradation of 

 this sort that always exists between the coastal and the offshore waters of the gulf. 

 Consequently the precise values recorded on Figure 98 represent the prevailing state 

 just prior to the date when surface saHnity begins to decrease. 



This profile also corroborates the horizontal projections of salinity (fig. 91 and 

 93) to the effect that in 1920 the cold Nova Scotian current did not begin to flood 

 westward past Cape Sable into the gulf before the end of March in volume sufficient 

 to affect the salinity of the latter appreciably, because the band less saline than 32.5 

 per mille (correspondingly low in temperature) was then narrower in the eastern side _ 

 of the gulf than in the western, or elsewhere around its periphery for that matter. 



