648 



BULLKTIN OF THE BUEEAU OF FISHEEIES 



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. 



IV1a.t<i-T« 



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 6 and 7, 1926 

 (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 



