258 bulletin: museum of comparative zoology. 



outside influences of any kind must be least active, is further evidence 

 that it is winter cooling by the air that is responsible in the main for 

 the cold water. And this same process equally well explains the gen- 

 eral persistence of low temperature in summer near shore below 

 twenty fathoms or so, solar warming progressing but slowly below 

 that depth, consequent on the progressive increase in the vertical 

 stability of the water. 



And how closely mean air and water temperatures agree, for 

 bays and sounds, is illustrated by Long Island Sound, where the 

 mean surface temperature for the year (52°-53°) is practically the 

 same as the mean air temperature for the year at New York. The 

 mean surface temperature in Massachusetts Bay is about 50°-52°; 

 the mean air temperature at Boston about 4.9°. In short, the tem- 

 perature of the coast water between Cape Sable and Chesapeake Bay 

 is not abnormally low, considering its relation to the land mass to the 

 west, and the winter climate of the latter. Hence it gives no direct 

 support to the upwelling theory. 



Neither is there anything in the surface temperature curves to 

 suggest such upwellings as those off California, off Morocco, and off 

 South Africa, for though the surface temperature is much lower over 

 some of the coast banks, and in the northeast corner of the Gulf of 

 Maine as a whole, than elsewhere, subsurface temperatures, salinities^ 

 and tidal currents prove that their cold surface is the result of violent 

 vertical circulation, accompanied by correspondingly high bottom 

 temperatures. Furthermore, the mean temperature is lowest where 

 there seems to be the least possibility of abyssal upwelling, i. e., in 

 partially enclosed basins next the coast. 



The rapid rise of surface temperature during July and August is in 

 itself a strong argument against the view that upwelling can have been 

 active at that time; and so is the great annual range of surface temper- 

 ature (30° for the Gulf of Maine, nearly 40° off New York, with an 

 even greater extreme range, Murray, 1898) ; for any considerable up- 

 welling of cold abyssal water would necessarily check the former, and 

 consequently lessen the latter. It would be hard to reconcile our sub- 

 surface temperatures with an upwelling over the upper part of the 

 continental slope at the time of our visit, whatever may have been the 

 case earlier in the season, because if such a process had been taking 

 place, the cold water over the shelf would have been continuous with 

 the cold water at greater depths further off shore, instead of separated 

 from the latter by the warm bottom zone, which was found south of 

 Cape Cod and Long Island; and which probably extended to Chesa- 



