BIGELOW: OCEANOGRAPHY OF MASSACHUSETTS BAY. 397 
once more reestablished itself. The minimum surface salinity was 
reached about May 5, near the Isles of Shoals, from which time on a 
rise is to be expected to the summer condition. 
There was no separation between the waters just outside the Isles 
of Shoals, and the channel between them and the mainland so far as 
surface salinity is concerned. But the salinity sections (fig. 5, 6) 
show that the progressive freshening was much more strictly a surface 
phenomenon outside the islands than it was nearer the mainland, 
as might be expected from the fact that the inshore stations lie 
near the mouth of the Piscataqua River. After about May 5, when 
the water was freshest, there followed not only a rise in surface salinity, 
but a progressive though slight increase in mean salinity of the whole 
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Fic. 6.— Salinity sections between the Isles of Shoals and the mainland, 
April 13 (Station 11 W. W. Welsh); April 16 (Station 13 W. W. Welsh); 
April 22 (Station 16 W. W. Welsh); April 23 (Station 17 W. W. Welsh); 
May 3 (Station 23 W. W. Welsh) and May 13 (Station 29 W. W. Welsh). 
column (Station 25 Welsh, mean 31.1%,; Station 26 Welsh, mean 
about 31.2% ,; Station 27 Welsh, mean about 31.4% , Station 28 
Welsh, mean about 31.4%,; Station 29 Welsh, mean 31.5%, ,; Station 
31 Welsh, mean 32.7% , the depths varying from 20-26 fathoms). 
And though the rise on the surface was once interrupted by heavy 
rain (Station 30 Welsh, May 16) the mean of 29 fathoms, 31.6%, 
was practically unchanged from the last station. The weather was 
stormy during the period May 5-15, with a northwest gale on the 
10th and 11th and 12th (7. e., Stations 27 and 28 Welsh), which may 
partly explain the rising salinity. But the fact that it continued to 
grow salter after this, except as just noted, shows that the spring in- 
flux of river water had passed its maximum, and was gradually being 
absorbed by the general circulation of the Gulf. 
