910 
BULLETIN OF THE BUREAU OF FISHERIES 
One other bottle is recorded by the United States Hydrographic Office (Pilot 
Chart for May, 1923; reverse No. 26) as showing a similar drift into the eastern side 
of the Gulf of Maine from its release, 34 miles south of Cape Sable, September 21, 
1902, to its recovery near Yarmouth, Nova Scotia, 30 days later. 
CIRCULATION OF THE SUPERFICIAL STRATUM AS INDICATED BY 
SALINITY 
The distribution of salinity affords a valuable check on the correctness of the 
circulatory system of the surface stratum, deducible from the drift-bottle experiments 
and from current measurements. The physical state of the water, together with 
the horizontal and vertical distribution of density, is the only clue yet available to 
the nontidal circulation in the deep strata of the gulf. 
The reader will find frequent references to this phase of the subject in the sec- 
tion devoted to the salinity (p. 701). The distribution of salinity, as a reflection of 
the circulation of the gulf, ; has also been discussed in such detail in earlier reports 
on the Gulf of Maine explorations (Bigelow, 1914 to 1922) that a brief statement 
will suffice here. 
With the oceanic water outside the edge of the continent much salter than the 
water in over the banks or alongshore (a rule prevailing all along eastern North 
America from Florida to the Grand Banks) a high salinity becomes an excellent 
indicator of any indraft from offshore. On the other hand, the lines of dispersal for 
land water are to be learned from the distribution of the least saline water. In the 
Gulf of Maine the flow of the Nova Scotian current past Cape Sable also tends to 
freshen the surface wherever its influence reaches. 
Our first summer’s cruise (in 1912) was enough to show what subsequent 
cruises have corroborated, that the freshest water is not localized off the mouths of 
the several large rivers, as would be the case if the discharges from these s im ply 
fanned out, but that it takes the form of a continuous and comparatively narrow belt 
skirting the coast line. The region where this freshest water does spread farthest 
out to sea (off Cape Ann and Massachusetts Bay) is some distance southward from 
the mouth of the Merrimac, the nearest of the large rivers. No fan of low 
salinity has ever been demonstrated off the mouth of the Kennebec. 
The absence of such a fan off the mouth of any given river may or may not 
prove the failure of its discharge to drift out to sea, depending on the balance between 
the activity with which the tides mix the deep with the surface strata there and 
the volume of fresh water discharged. The river water that runs into the northern side 
of the gulf, and especially into the Bay of Fundy, is rapidly consumed in this way. 
Nevertheless, even where mixing is most active, areas of relatively lower salinity off 
the river mouths might be expected to alternate with areas relatively higher in 
salinity along the coast sectors between them, unless some dominant drift in one 
direction or the other disturbed this idealized picture. When we recall how great 
a volume of fresh water actually pours into the Gulf of Maine every year (p. 837) it is 
hardly conceivable that it would exert its chief freshening effect on so narrow a 
coastwise belt, unless the surface water tended to drift parallel to the land in the one 
direction or the other. 
