646 
BULLETIN OF THE BUREAU OF FISHERIES 
bay (Nos. 16 and 17) were then fractionally cooler at the surface than deeper — evi- 
dence that the water had been rapidly losing heat from the surface for some days 
previous, which can be associated with a cold northwest gale on November 23. No 
great horizontal variation in temperature was to be expected over so small an 
area; in fact, all the readings for this cruise fell within the limits of 4.80° and 6.93°. 
The slight differences recorded from station to station on this cruise prove unex- 
pectedly instructive, because the coldest water (4.8° to 5.8°) then formed a more or 
less definite pool close 
1 ° 
Temperature, Centigrade 
3° 4° 5° 6° 7° 8° 
10 ° 11 * 
inshore, a few miles 
north of Plymouth, 
with appreciably 
higher temperatures 
(6.8° to 6.9°) to the 
northward as well as 
off the mouth of Ply- 
mouth Harbor and in 
Cape Cod Bay to the 
south. Although the 
data do not suffice to 
bound this cold area 
offshore, the general 
distribution of tem- 
perature to be ex- 
pected at that season, 
and actually recorded 
there later in the 
month (fig. 7 6) , makes 
it virtually certain 
that it was also en- 
tirely surrounded by 
higher temperatures 
to the east. 
On this same day 
(December 3), C. G. 
Corliss, superintend- 
ent of the Gloucester 
hatchery, found the 
surface water 4.4° in 
Gloucester Harbor 
and 5.6° at a locality 
1 to 2 miles off its 
mouth, a gradation that illustrates the progression of winter cooling from the land 
out to sea, but does not suggest any considerable thermal difference between the 
two sides of the bay at the time. Unfortunately, no corresponding readings were 
taken in the central part; but the water was about 2° warmer 7 miles off Glouces- 
Fiq. 75. — Vertical distribution of temperature in the offing of Gloucester on successive dates of 
the autumn and winter. A, October 1, 1915 (station 10324); B, November 20, 1912 (station 
10047); C, December 4, 1912 (station 1C048); D, December 23, 1912 (station 10049); E, 
December 29, 1921 (station 10489); F, January 16, 1913 (station 10050); G, February 9, 
1921; H, February 13, 1913 (station 10053) 
