944 
BULLETIN OF THE BUREAU OF FISHERIES 
MAY 
Progressive incorporation of river water into the northern and western sides of 
the gulf, coupled with vernal warming, constantly favors the anticlockwise move- 
ment of the so-called "spring current” (fig. 194); and with the resultant changes 
in salinity and temperature affecting chiefly the surface, the site of the chief dynamic 
impulse toward circulation shifts from the deep strata to the superficial. In May, 
1915, for example, a difference of about 1.5 units of density was recorded at the 
surface between the vicinity of the mouth of Massachusetts Bay and the basin in 
Fig. 192— Dynamic gradient at the surface of the gulf, April 6 to 20, 1920, referred to the offing of the Bay of Fundy 
as base station. Contours for every dynamic centimeter 
its offing (fig. 194) in a distance of 30-odd miles, but only about one-seventh as wide 
a difference at the 50 or 100 meter levels (stations 10266 and 10267). 
As a result, the dynamic chart for May (fig. 195) corresponds closely to the dis- 
tribution of density at the surface, except for the relationship between the shallows 
of German Bank and the deep water immediately to the west of the latter. In this 
region the surface projection, taken by itself, would give a false picture, being con- 
fused by the strong tides that keep the water thoroughly stirred over the bank, thus 
