PHYSICAL OCEANOGRAPHY OF THE GULF 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 chilling 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° T 8° 9° 10° 11° 12° 13° 14° 15° 16° 17° 
Meter 0 
10 
20 
30 
40 
50 
60 
70 
80 
90 
100 
110 
120 
130 
140 
150 
160 
Fig 71. — Vertical distribution of temperature off 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, 
1916 (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 cooling after October 3 as follows: 
Depth 
Oct. 3, 
19161 
Oct. 16, 
1916> 
Oct. 21, 
19161 
Oct. 27, 
19161 
20 meters 
° C. 
10.60 
9.83 
9.82 
°C. 
9.35 
9. 14 
8.98 
°C. 
9. 32 
9.08 
18.88 
°C. 
8.51 
8. 81 
8. 80 
30 meters - 
1 From Vachon’s (1918) tables. s 26 meters. 
