164 



bulletin: museum of comparative zoology, 



Bottom temperature. The chart of bottom temperature (Fig. 8) illus- 

 trates the localization of cold bottom water on the mid-zone of the 

 continental shelf south of Long Island and Marthas Vineyard in 

 July, the southern boundary of which must have been somewhere 

 between the latitude of New York and the line off Barnegat. Shore- 

 ward as well as seaward, the bottom water was warmer than 45°. 

 That this should have been the case nearer land was to be expected, 

 because of the steady shoaling of the water. But the fact that the 

 bottom water was warmer (50°-51°) between 50 and 125 fathoms 



Fig. 10. — Temperature profile across the outer part of the continental slope 

 southwest of Nantucket (Stations 10063, 10062, 10061). 



than at 35-50 fathoms, would have been a surprise had not a similar 

 phenomenon been encountered by Libbey (1891) south of Marthas 

 Vineyard in 1889 (p. 241). As pointed out (p. 165) this cold bottom 

 water was not continuous with the cold water in the Gulf of Maine, 

 being interrupted on Nantucket shoals, where the bottom tempera- 

 ture is raised, and the surface correspondingly chilled, by vertical 

 tidal mixing. But no doubt, in winter, the cold water is continuous 

 across the shoals. On the continental slope the temperature was 45° 

 at about 200 fathoms. 



