178 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
The distribution of the fifteen fathom mean, highest in the central 
part of the Gulf (Stations 10088 and 10093), falling to about 54°-55° — } 
over the western half of the Gulf generally, and lowest in its northeast 
corner and on German Bank, corresponds with the distribution of 
surface temperature, and with the proportional strength of the tidal 
currents, just as might be expected, solar warming being most effective 
where vertical circulation is least active. 
Temperature profiles. The general distribution of temperature 
across the Gulf, from east to west, is illustrated by a profile from 
Massachusetts Bay to German Bank (Fig. 21, Stations 10106, 10087, 
10088, 10090, 10092, 10093, 10094, 10095), its most interesting feature 
being its illustration of the fact (p. 172) that in the central part of the 
Gulf the water was coldest at about fifty fathoms, not on the bottom. 
Water of 41°-48° filled the sink at the mouth of Massachusetts Bay, 
rising there to within twenty-five fathoms of the surface; and projected 
eastward, like a shelf, over the western basin, without any rise in 
temperature at fifty fathoms as far east as Station 10088; warming 
to 43.5° in the middle of the Gulf (Station 10090). In the eastern half 
of the profile, the coldest water extended from shore, westward into 
the centre of the Gulf. But on this side there was no water colder 
than 42°, the lowest reading being 42.°, and the cold mass of water was 
not horizontal but oblique, rising from a depth of 80-100 fathoms on 
the shore slope, to 40-60 fathoms at its western end, with the coldest 
water (42°) limited to a very thin layer 40-50 fathoms. The cold 
layer was interrupted in the middle of the Gulf (Station 10090) by 
water 1°-2° warmer at the fifty fathom level. The temperature of 
the water underlying the cold zone ranged from 43° to 43.9°, coldest 
at the eastern side of the Gulf, depth for depth, warmest in the centre 
(Station 10090), 7. e., just the reverse of the temperature at fifty 
fathoms. 
Above thirty fathoms the water was warmest at Station 10088, 
coldest on German Bank and off the mouth of Massachusetts Bay 
(Station 10087), where the temperature was below 43° at a depth of 
only twenty-five fathoms. The profile shows the spreading of the 
curves over German Bank (Station 10095) which characterized that 
region in 1912 (1914a, p. 56); caused by vertical mixing by the tides. 
And there is a similar phenomenon in Massachusetts Bay (Station 
10106); limited in this case to depths below ten fathoms. 
A profile running northeast from the mouth of Massachusetts Bay 
to Station 10089 (Fig. 22) shows that water colder than 42° extended 
unbroken across the northern end of the western basin, to the south- 
