BIGELOW: COAST WATER EXPLORATION OF 1913. 237 



between Cape Cod and Chesapeake Bay, so far as known, may be sum- 

 marized as follows : — in February, the coldest season of the year, 

 the temperature of the water is very low indeed close to the coast and 

 in the bays and sounds, 31°-36° near Woods Hole, rising, toward the 

 southwest, to about 35° near New York (Rathbun, 1887); about 36° 

 off Cape May, 37°-38° at Winter Quarter Shoal; and even south of 

 New York, freezing temperatures may occur near shore during very 

 cold weather. But such low temperatures are limited to a very 

 narrow belt, the winter temperature over the continental shelf as a 

 whole being 40°-45°, rising suddenly to about 50° over the conti- 

 nental slope. And, of course, the surface water is still warmer further 

 to the east and southeast, i. c, in the Gulf Stream. With the advance 

 of spring the temperature of the shore water rises steadily, until by 

 the first part of July, the water over the continental shelf ranges, in 

 temperature, from 75° off Chesapeake Bay to 68°-70° south of Marthas 

 Vineyard. During mid-summer the temperature is locally higher 

 next the coast than it is over the shelf, often even higher than the 

 surface water of the Gulf Stream in these latitudes. For instance, the 

 temperature immediately off Chesapeake Bay, in July, 1913, rose to 

 80°; off New York to 75°; off Long Island to 76°-71°. And the summer 

 warming of such enclosed waters as Woods Hole and Nantucket 

 Sound outstrips the rise of temperature over the shelf, until, as the 

 summer advances, the shoreward movement of Gulf Stream water may 

 obliterate this difference by raising the surface temperature over the 

 shelf as a whole to 70° or over. And Gulf Stream water, with its 

 characteristic plankton, often floods Narragansett Bay and Vineyard 

 Sound in late summer, though the extent to which this happens dif- 

 fers from year to year, depending on the direction of the wind. The 

 surface temperature of the coast water reaches its maximum in 

 August. 



To the student of ocean circulation one phenomenon in this annual 

 cycle is of great importance, namely, the fact that where the water 

 cools most rapidly, and to the greatest degree, in autumn and winter, 

 i. e., close to the shore, there it warms up most rapidly in spring and 

 summer. 



A large number of subsurface temperatures have been taken in the 

 waters south of Marthas Vineyard, beginning with a series of bottom 

 readings, by the vessels of the U. S. Bureau of Fisheries, in 1880, 1881, 

 and 1882; and continued by Libbey (1891, 1895), who took several 

 thousand readings at intermediate depths in 1889, 1890, and 1891. 

 But these were all made in summer and early autumn; and our 



