236 bulletin: museum of comparative zoology. 



study of diurnal warming and nocturnal cooling, to make them com- 

 parable with one another. But this is not necessary here, because, 

 after all, they are not strictly comparable with our observations, 

 having been taken from three to six weeks later in the season, and hence 

 may be expected to be higher. They suggest that the surface water 

 in that year may have been rather cooler than we found it, for Libbey 

 (1891) found much the same temperature at the end of July that was 

 observed in the first half of the month; i. e., July 24, 1881, 62.8° at 

 the 25 fathom curve south of Nantucket; 66°-67° over the outer 

 half of the shelf; 68° at the 100 fathom curve. 



A large number of surface temperatures have been collected by 

 Dickson (1901) for the years 1896, 1897. In July 1896, according to 

 his charts, the surface temperature from Marthas Vineyard to New 

 York was between 60° and 68°, above 68° off New Jersey. By August 

 it had risen to 68°, the greater number of the records having been 

 taken, no doubt, along the direct steamship line from Nantucket light- 

 ship to Fire Island light-ship. In 1897 the water was warmer, being 

 upwards of 68° from Nantucket to New York. According to the 

 British Meteorological office (Sumner, Osburn, Cole, 1913, p. 438) the 

 mean surface temperature, some thirty miles south of Marthas Vine- 

 yard, is 67° in July, 69° in August: 66° and 70° respectively in Long 

 Island Sound; 71° and 73° in the mouth of Delaware Bay; 75° for 

 both months over the 100 fathom curve off Chesapeake Bay. 

 Hautreux (1911) gives the average surface temperature, for a five- 

 year period, off Fire Island light-ship, as 66.2° for both July and 

 August. How closely the temperatures obtained in July, 1913, agree 

 with Sumner's averages is illustrated by the fact that we had pre- 

 cisely the same reading off Fire Island light-ship; off Marthas Vine- 

 yard (Station 10063, 67°) ; off the edge of the continental slope abreast 

 of Cape May (73°) ; and the difference off Chesapeake Bay was only 

 l°-2°. And they lie within the range for 1896, as given by Dickson, but 

 are colder than his records for 1897. On the other hand the water 

 was warmer off New York in 1913 than the five-year average given 

 by Hautreux, 69° instead of 66.2°. 



The summer temperatures outlined above are enough to show that 

 1913 may be considered a perfectly normal year; 1881, 1884, and 1889 

 were cooler, and 1897 warmer. And in view of the fact that in summer 

 the surface temperature over the continental shelf depends largely on 

 the wind, it is doubtful whether the very slight differences between 

 these years have any general significance. 



The general range of surface temperature over the continental shelf 



