PHYSICAL OCEANOGRAPHY OP THE GULF OF MAINE 
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shoaler strata of water, reproducing the vertical distribution found there (though 
somewhat more saline in actual values) in March and April of 1920 (stations 20064 
and 20112), hence this type is probably characteristic of that part of the gulf. 
The state of the deep water in the two channels — eastern and northern — that 
interrupt the offshore rim of the gulf is worth stating, these being the possible sources 
for deep undercurrents flowing inward. In July, 1914 (our only late summer stations 
for this locality) , the vertical distribution of salinity was almost precisely the same 
in the Eastern Channel as in the southeastern part of the gulf, into which the latter 
debouches, as were the actual values at different depths, with so little difference 
between the values in the channel for the months of March, April, June, and July 
in different years (fig. 141) as to prove the salinity of its deeper strata virtually 
Fig. 141. — Vertical distribution of salinity in the Eastern Channel. A, April lfi, 1920 (station 20107); 
B, June 25, 1915 (station 10297); C, July 24, 1914 (station 10227) 
unchanging there through spring and summer. The Northern Channel, on the other 
side of Browns Bank, at the same date (station 10229, July 25, 1914), was about 1.5 
per mille less saline than the Eastern Channel on bottom (100 meters), though only 
about 0.5 per mille less so at the surface. 98 Consequently, any drift over the bottom 
via this route would have brought water much less saline to the gulf, as is also the case 
in spring (fig. 99). 
Our late summer stations yielded almost precisely the same salinity on Browns 
Bank (station 10228) as in the Eastern Channel to the west of it and in the neigh- 
boring part of the basin of the gulf, correspondingly salter than the Northern Channel 
to the north (cf. fig. 141 with fig. 142), evidence of an overflow from the Eastern 
18 32.47 per mille at the surface at station 10227; 32.01 per mille at station 10229. 
