614 



BULLETIN OF THE BUEEAU OF FISHERIES 



In August, 1914, however, the bottom water was appreciably warmer (7° to 

 7.9°) in the eastern and northeastern parts of the basin than in the western and 

 central parts (6° to 6.24°), apparently banking up against the Nova Scotian slope, 

 as indicated on the chart (fig. 57). Successive stations, from the offing of Cape 

 Ann to the Nova Scotian slope, again showed a slight rise in the temperature of the 

 of the bottom water (at 175 meters) from west to east across the basin on August 

 31 to September 2, 1915, as follows: Station 10307, 5.4°; station 10309, 5.8°; and 

 station 10310, 6.8°. The amount by which the temperature of the one side of the 

 gulf differs from that of the other, in this stratum, varies so widely from year to 

 year that it would not be surprising to find it virtually uniform over the whole area 

 of the basin in some future summer. 



Other features of the temperature at 175 meters worth mention are its con- 

 stancy in the southwestern part of the basin from July 19 (station 10214, about 5.4°) 

 to August 23 (station 10256, 5.6°) in 1914, and the fact that the southeastern part 

 was warmer than the Eastern Channel in that summer,'* although the latter offers 

 the only route by which water of high temperature can flow into the gulf from off- 

 shore. Barring the possibility of higher temperature in one or the other sides of the 

 channel than in its center, where the observations were taken, the most reasonable 

 explanation for this apparent anomaly is that a considerable indraft had taken place 

 late in June, but that this had then slackened, allowing the temperature of the 

 channel to be reduced slightly by mixture with the cooler water to the east and 

 west of it. 



Our data for 1914, combined with temperatures taken south of Marthas 

 Vineyard by Libbey (1891) in 1889, show the water along the continental edge 

 abreast of the gulf as 10° to 11° at the 175-meter level in late summer, warming to 12° 

 a few miles farther offshore (fig. 57). In 1914 the mouth of the Eastern Channel 

 marked a division at this and greater depths between these comparatively high 

 temperatures to the west and lower temperatures to the east, with the isotherms 

 swinging offshore, abreast of Browns Bank, and a 175-meter value of only about 

 7.7° in the offing of Shelburne on July 28 (station 10233). But with the tempera- 

 ture between 11.3° and 11.85° there at this same level and at about the same date 

 a year later (Bjerkan, 1919, p. 393; Acadia station 41), the ocean water was 

 evidently closer in to the slope — annual variation sufficient to exercise considerable 

 biologic effect on the bottom fauna along the southeastern slopes of Browns Bank 

 and Georges Bank. 



Only a small portion of the basin of the gulf is deeper than 175 meters. The 

 bottom of the western bowl, at 260 meters (entirely inclosed at this level), was 7° 

 in August, 1914, that of the eastern branch ranging from about 6° in its western 



"Station 10225 about 8.8° and station 10227 about 7.1° at 175 meters on July 23 and 24, 1914. 



