690 
BULLETIN OF THE BUKEAU OF FISHERIES 
The evidence just outlined leads to the conclusion that the Nova Scotian water 
flowing into the Gulf of Maine from the eastward in spring does not lower the gen- 
eral temperature of even the coldest localities and levels in the gulf more than a 
degree or two below the values that would prevail were the gulf as nearly inclosed 
as are the Black Sea or the Norwegian fjords. Nevertheless, the Nova Scotian 
current does act as a decidedly effective cooling agent, for without the cold 
water from this source the comparatively high temperature of the slope water, of 
the surface inflows from the region off Browns Bank, and of occasional overflows of 
tropic water (p. 836), would hold the gulf several degrees warmer than it actually is. 
These warm sources the Nova Scotian current counteracts, and in counteracting 
them it has its chief thermal importance in the Gulf of Maine. 
THERMAL EFFECT OF THE SLOPE WATER 
Were the gulf an inclosed basin, with little or no inflow over its floor, we should 
expect to find its bottom temperature certainly no higher then 5° to 6° and proba- 
bly as cold as the mean annual temperature actually is in the deep sinks in the 
western side of the gulf, namely 4° to 5° (p. 688). In reality, however, we have only 
once found the bottom water in the basin of the gulf colder than 4° in depths of 
175 meters, or deeper, at any locality, season, or year. 71 Only 4 out of 64 deep 
stations in the basin have given bottom readings lower than 4.5°. On the other 
hand, 26 have been warmer than 6° on bottom; and the bottom temperature for all 
as deep as 175 meters has averaged about 6°, or 1J^° warmer than the mean annual 
temperature at the 100-meter level around the shores of the gulf and 2° warmer 
than the mean bottom temperature in the trough of the Bay of Fundy. The high 
salinity, coupled with the precise temperature of this bottom water, identifies it 
beyond dispute as slope water flowing in along the trough of the Eastern Channel 
(see discussion p. 842). The slope water, then, brings warmth to the deeps of the 
gulf sufficient to raise the bottom temperature of the basin a degree or two higher 
than would be the case if no such current flowed in; consequently it must be named 
a warm current as it affects the gulf, not a cold one. 
The physical characteristics of the slope water, as it drifts inward along the 
bottom of the Eastern Channel, have proved so uniform from season to season and 
from year to year (temperature about 6° to 7° and salinity about 34.6° to 35° per mille 
in spring and summer) that the causes for the variations recorded in the temperature 
and salinity of the deepest water within the gulf are to be sought in fluctuations in 
the volume and velocity of the inflowing bottom drift rather than in variations in 
the temperature or salinity of the latter. Such fluctuations, in turn, almost certainly 
have a two-fold cause. In part they result from corresponding variations in the 
amount of slope water being manufactured along the continental slope to the east- 
ward shortly prior to the date of observation, and in the proportional amounts of 
the various waters, cold and warm, that enter into its composition. The seasonal or 
or other secular differences in the density gradient over the continental slope from 
Browns Bank to La Have Bank, however, probably play a more important role in 
71 Bottom temperature 3.54° at 180 meters at station 10283 off the Bay of Fundy, June 10, 1915. 
