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 jjrofiles. 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°-43° 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 low^est 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°) Hmited to a very thin layer 40-50 fathoms. The cold 

 layer was interrupted in the middle of the Gulf (Station 10090) by 

 water l°-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), i. c, 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- 



