BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 49 



(3) For every month of the year the water temperatures at Gloucester are higher 

 than those at Boothbay. On the other hand, during the months of December, Janu- 

 ary, February, and March the Woods Hole temperatures are lower than those reported 

 from Gloucester, despite the more northerly location of the latter station. This is 

 probably due to the fact that the water used at the Gloucester station is in more imme- 

 diate connection with the great reservoir of ocean water, which responds more slowly 

 to the winter cold. Moreover, a rapid intermingling of the two is effected by the tides, 

 which have a far greater amplitude at Gloucester than at Woods Hole." 



(4) During the months of May to November, inclusive, the water temperatures at 

 W'oods Hole are much higher than those of either of the more northerly stations, while 

 the mean difference between Woods Hole and Gloucester for July, August, and Sep- 

 tember (7.1°) is over twice as great as that between Gloucester and Boothbay (3.5°).* 



This last feature of the comparison is the most important of all for our present 

 purposes. The difference in latitude between Woods Hole and Gloucester is about 

 1° 7', while that between Gloucester and Boothbay is about 1° 12'. Nevertheless, the 

 difference in water temperature between those two stations, which are separated by 

 the peninsula of Cape Cod, is twice as great during the three months of the year when 

 the water is warmest as that between the two stations lying to the north of Cape 

 Cod, even though the latter are divided by a greater interval of latitude. While the 

 waters whose temperatures are here recorded may not be entirely representative of the 

 neighboring sea areas, and while the number of years here comprised is small, the main 

 points in our comparison are believed to be sufficiently well established. Let us now 

 return to a consideration of the temperature conditions at Woods Hole. 



Significant features of the local temperature conditions. — If we take the average of 

 all the temperature determinations (surface and bottom) recorded on chart 211 for the 

 14 stations westward of Robinsons Hole, within and at the entrance to Vineyard Sound, 

 we find the mean temperature of these waters, at practically the period of maximum 

 temperature, to be 62.17.° At Woods Hole this temperature is exceeded during the 

 entire period of the year between June 14 and October 6. If we consider only the 

 figures for bottom temperature in this western area of the Sound (and these it is, in the 

 main, which influence the bottom fauna), we find the mean to be 60.24, ^ temperature 

 which is exceeded at Woods Hole, from June 3 to October 11. In Buzzards Bay, on 

 the other hand, a temperature as low as this last was not once recorded during the 

 August series of observations, though in one case it was found just beyond the mouth 

 of the Bay (V). Bottom temperatures between 60° and 65° were, however, found 

 throughout the lower third or fourth of the Bay, except near the western shore. 



It thus appears that the summer conditions of temperature such as obtain in the 

 vicinity of Woods Hole during the months of June, July, August, and September do 

 not directly affect the southwestern third of Vineyard Sound and in only a limited 

 degree tlic lower end of Buzzards Bay. It will be shown that this fact is of supreme 

 importance for the understanding of certain features of distribution. 



It might reasonably have been expected that the winter temperature of these 

 outlying waters, adjacent to the open sea, would be considerably higher than that 



a This is in full agreement with the explanation of the relatively high winter temperatures at Gloucester and Boothtjay; 

 independently offered by Superintendents Corliss and Hahn, 



6 This difference is likewise somewhat greater for October, and is practically the same for May. 



16269° — Bull. 31, pt I — 13 4 



