PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 
563 
Georges Bank, also; and the presence of a band of water cooler than its immediate 
surroundings along the outer side of the latter bank and off Marthas Vineyard in sum- 
mer (p. 608) suggests its influence. 
It is still an open question how far westward into the gulf the vernal warming 
of the surface is retarded by this same agency. Even without its chilling effect, the 
surface probably would not warm as rapidly in the eastern side of the gulf as in the 
western, because the heat received there from the sun is more rapidly dispersed down- 
ward by more active vertical tidal stirring. Consequently, a slight west-east differ- 
ential in surface temperatures, late in spring or early in summer, does not necessarily 
Fig. 32. — Normal rise in surface temperature from mid-April to mid-May. The hatched area experiences cooling 
imply cold water from the eastward as its cause unless it reflects a corresponding 
difference in the mean temperature of the upper 40 to 60 meters. 
Up to the present time we have found no positive thermal evidence of the Nova 
Scotian water beyond the eastern arm of the basin (the situation of ice patrol station 
No. 3, p. 997) ; and the temperature (salinity, too) of the gulf is so uniform from sum- 
mer to summer that vernal chilling from this source is not to be expected farther west 
than this, unless an exceptional spring may see a much greater inflow of cold water 
from the east than usual past Cape Sable. 
