770 
BULLETIN OF THE BUREAU OF FISHERIES 
In the northwestern part of the gulf variations in the distribution of salinity 
from summer to summer show that the movements of the surface water are variable 
in detail. 
Thus, in July and August, 1912, the isohaline for 32.4 per mille (the critical one 
in this particular summer) marked a definite expansion of coastal water off Penobscot 
Bay (Bigelow, 1914, pi. 2). In August, 1913 (fig. 135), the undulations of the 
isohaline for 32.5 per mille again suggested an anticlockwise swirl off the bay, drawing 
salter water into its northern and eastern sides, fresher water into its western and 
southern sides. In August, 1914 (fig. 136), the surface salinity of this part of the 
gulf was more uniform, with no evidence of any such outflow off the Penobscot; nor 
is anything of the sort indicated in the surface chart for 1915 (fig. 137). 
In the Massachusetts Bay region, by contrast, the regional distribution of salin- 
ity at the surface has been more nearly constant from summer to summer. Thus, 
in August, 1922 (apparently a representative year in this respect), when the surface 
at 13 stations ranged from 30.95 to 31.29 per mille, the distribution was of the usual 
coastwise type— i. e., slightly lowest (30.9 to 31 per mille) close to Gloucester (sta- 
tion 10633), off the mouth of Boston Harbor (station 10638), and close to land in 
Cape Cod Bay (stations 10643 and 10644) ; uniformly slightly higher across the mouth 
of the bay (31.2 per mille at stations 10631 and 10632). Three stations on a line 
crossing the mouth of the bay on August 31, 1912, showed no greater variation than 
this on the surface, though all of them gave slightly higher readings (31.67 to 32.03 
per mille). It is probable that the surface of the bay would have been found less 
saline than this in August, 1916, judging from a surface reading of 31.27 per mille off 
the tip of Cape Cod on the 29th (station 10398) and from the fact that the mouth 
of the bay had been only 30.5 to 31.2 per mille a month earlier (stations 10340 to 
10342). In 1913 the August value was somewhat higher at the mouth of the bay — 
i. e., about 32.1 per mille. 
Observations taken in the offing of Nantucket and on the northwestern part 
of Georges Bank in July of 1913, 1914, and 1916 show all this area included within 
the influence of the low salinity of the coastal belt, with surface values close to 
32 per mille over Nantucket Shoals, rising to 32.1 to 32.5 per mille over the 
neighboring parts of Georges Bank (fig. 136; Bigelow, 1922, fig. 36). Surface 
readings make it probable that in July, 1914 (fig. 136), the band of low temperature 
described above (p. 608) as crossing the bank from northeast to southwest was 
reflected in an expansion of low salinity from the southwestern part of the bank 
out across its seaward slope, as outlined by the isohaline for 33 per mille. 
It is probable that the regions of low surface temperature over the shoaler 
parts of Georges Bank, where the water is churned by strong tidal currents (p. 594), 
are equally characterized by a surface salinity higher than that of the general 
neighborhood. Our visits thither have afforded two instances that may be inter- 
preted in this way — namely, a slightly higher value at one station on the eastern 
part (32.59 per mille at station 10223) on July 23, 1914, than at neighboring stations 
to the north, south, or east of it, and a value equally high on the western side on the 
same date of 1916 (station 10348, 32.54 per mille), again with slightly less saline 
surface water to the south, west, and apparently to the north. A similar pool of 
