70 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
fathom curve from Mt. Desert Island to the southwestern end of the 
Grand Manan Channel. 
Over the central part of the Gulf, including Platt’s Bank as well as 
most of the 100-fathom basin, the salinity at twenty-five fathoms was 
above 33°. But the curve for that value runs off shore far enough to 
exclude the whole of Jeffrey’s Bank, thus suggesting the southerly 
swing of the curve of 32.4 on the surface, though not exactly duplicat- 
ing it. It then turns northward toward the coast, including in its 
sweep the whole of the eastern branch of the deep basin, as well as 
part of the coastal bank off Nova Scotia. The saltest water found at 
this depth was not at Station 31, as was the case on the surface, but 
at Station 28 (33.4). In spite of this discrepancy, however, the 
twenty-five fathom level corresponds to the surface in the presence of ° 
intrusions of comparatively fresh water off Cape Ann and off the mouth 
of the Penobscot, and in the fact that the saltest water was over the 
eastern edge of the 100-fathom basin. 
Salinity at fifty fathoms.— The curves at fifty fathoms (Plate 3) show 
the same influx of fresh water off Massachusetts Bay as do the charts 
for twenty-five fathoms and for the surface, though to a less degree. 
But I must point out that the charts for the different levels are not 
strictly comparable with one another in this region, because almost 
the whole of Massachusetts Bay, as well as the long ridge formed by 
Jeffrey's Ledge, running some forty-five miles northeasterly from Cape 
Ann, is shallower than fifty fathoms. The salinity over most of the 
Gulf at this level was above 33. But along the shore from Cape Ann 
northward, in the trough west of Jeffrey’s Ledge and as far as Monhe- 
gan, the salinity was lower, between 32.8 and 33.; and in the isolated 
basin in the mouth of Massachusetts Bay (Station 2), the salinity 
at fifty fathoms was 32.8. The curves at this level hardly show the 
southerly swing off the mouth of Penobscot Bay so pronounced at 
higher levels, the curve for 33 running parallel to the coast, along the 
fifty fathom line, from Matinicus Rock eastward. This fact, of course, 
shows that the fresh water from the Penobscot had little or no influence 
at this depth, although its presence was evident nearer the surface. 
Over the eastern branch of the 100 fathom basin the fifty fathom salin- 
ity was above 33.6, the highest being 33.8 at Station 28, while at 
Station 31, so salt at the surface, the fifty fathom reading was only 
33.5. The lowest salinity at this depth was in the Grand Manan 
Channel, 32.65, practically the same as at the surface. 
Bottom salinity — The bottom salinities of the Gulf of Maine 
(Plate 3) are largely dependent on depth, for, as we have seen, there 
