714 BULLETIN OF THE BUREAU OF FISHERIES 



per mille in the topographic bight just east of Cashes Ledge) to 34 to 34.2 per mille 

 in the southeast corner (station 20064) and to 34.5 per mille in the eastern side of 

 the Eastern Channel (station 20071). It is probable, however, that a band of slightly 

 fresher water skirted the western slope of the latter down to this depth, as it 

 certainly did the southeastern face of Georges Bank, a phenomenon discussed 

 below (p. 848, 938). 



At depths greater than 200 meters the contour of the bottom divides the trough 

 of the gulf into three separate basins: The 200-meter salinity fell between 33.7 per 

 mille and 34.7 per mille in February and March, 1920 — lowest (33.8 to 34.1 per 

 mille) and extremely uniform in the western and northeastern channels, highest (33.2 

 to 34.7 per mille) in the southeastern and in the eastern channels, as was naturally 

 to be expected. 



Water salter than 35 per mille (i. e., of nearly full oceanic salinity) washed the 

 slope at this level off the southwest face of Georges Bank, but was separated from the 

 southeastern slope by a wedge of considerably lower salinity (34.6 to 34.7 per mille, 

 station 20069), much as is described above for the shoaler levels (p. 704; figs. 93 to 

 95). And with the whole column less saline than 35 per mille right down to a depth 

 of 1,000 meters at this location, and also a few miles to the eastward of the mouth 

 of the Eastern Channel (station 20077), it is evident that a very considerable mass 

 of water of about the salinity that usually characterizes the bottom of the Gulf of 

 Maine then filled the entire submarine triangle at the mouth of the only possible 

 inlet into the deeps of the latter. This is a significant phenomenon because it is 

 from this source of moderate salinity (34.5 to 35 per tnille), not from pure oceanic 

 water, that the bottom drift into the gulf draws, as is described more in extenso below 

 (p. 842). With this moderate salinity extending downward so deep (fig. 92), it is 

 evident that considerable upwelling might take place off the mouth of the channel 

 without bringing into the latter (and thus into the gulf) water of appreciably higher 

 salinity than a more nearly horizontal inflow would bring. 



Only a very small part of the gulf is much deeper than 200 meters. The bottom 

 water, at 250 meters, was 34 to 34.2 per mille in both the western and the eastern 

 bowls in March, 1920 (stations 20054 and 20087), with higher values in the south- 

 eastern part of the gulf ,^* corresponding very closely to the salinity of the bottom of 

 the Eastern Channel (34.7 per mille) and outside the latter. 



PROFILES 



The charts for the several levels give a picture of the sahnity in horizontal 

 projection, but the spacial distribution is made more graphic by representation 

 in profiles. 



The essential contrast between the low salinity that characterizes the Gulf of 

 Maine at all seasons and the much more saline oceanic water to the seaward of the 

 continental edge is illustrated for February and March by two profiles running from 

 north to south across the gulf and its southern rim, the one from the offing of 

 Cape Elizabeth (fig. 96), the other from the offing of Mount Desert Island. 

 (Fig. 97.) Taken in conjunction with the corresponding profiles for temperature 



w station 20064, salinity approximately 3J.S per mille from 250 meters right down to the bottom in 330 meters. 



