PHYSICAL OCEANOGEAPHY OF THE GULP OF MAINE 



641 



the case in the deeps of the open gulf. Probably this process continues into Septem- 

 ber every year, sometimes into October, as happened in 1916 (Vachon, 1918, tables, p. 

 309), with the bottom water continuing to warm for some time after the surface has 

 commenced to cool. Judging from Mavor's (1923) tables, the depths greater than 

 about 60 meters in the trough between Grand Manan and the Nova Scotian shore 

 of the bay may be expected to warm by about 1° after the date when the surface read- 

 ing is highest and before the deep layers also commence to show the chiUing effect 

 of autumn. In 1917 the temperature of the mid-stratum rose from about 6° to 7° 

 there on September 4 to 7°-8° on October 2, but the maximum (6° to 7°) was not 

 attained at depths greater than 60 meters until some weeks later in 1916. 



Temperature, Centigrade 



1» 2° 3° 4° 5° 6° 7° 8° 9° 10° IT 12° 13° 14° 15° 16° 17° 



It 



Fig 71. — Vertical distribution of temperature oil Penobscot Bay at successive dates, to show the progress of 

 autumnal cooling. A, August 14, 1914 (station 10250); B, October 9, 1915 (station 10329); C, November 2, 

 1910 (station 10402); D, January 1, 1921 (station 10496) 



In the lower part of Passamaquoddy Bay, Vachon (1918; Prince station 4) found 

 the whole column in 30 meters depth coohng after October 3 as follows: 



1 From Vachon's (1918) tables. 



: 26 meters. 



