648 
BULLETIN OF THE BUBEAU OF FISHERIES 
the form of an isolated pool near the western shore, surrounded by slightly higher 
temperatures (fig. 76). Equally cold water (about 5.3°, surface to bottom) off 
the mouth of Provincetown Harbor (station 5) now marked the shallows of the 
latter as a second center for local cooling. 
After cold west winds on December 13, 14, and 15, the whole column of water 
averaged about 1 degree colder in the southern half of the bay on the 16th and 
17th than it had been a week earlier, with a maximum cooling of about 2° and a 
minimum of about 1° at the surface. 
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Fig. 77.— Vertical distribution of temperature at three representative stations in the southern 
side of Massachusetts Bay on December 9 to 11, 1924 (solid curves), and January G and 7, 1925 
(broken curves). 
Meantime the eastern and southern parts of Cape Cod Bay (5° at the surface) 
had definitely become a site of production for cold water, separated from the still 
colder pool next the land north of Plymouth (3.8° to 4.5°) by a slightly warmer 
wedge (5° to 6°) in the center of the bay. At this season the water of the bay is so 
nearly homogeneous, surface to bottom (fig 77), that a chart of the minimum tem- 
perature, irrespective of depth (fig. 78), illustrates this regional distribution better 
than a surface chart can. 
When the temperature varies more widely between stations a few miles apart 
than between surface and bottom at any one station, as is the case in the southern 
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