672 
BULLETIN OF THE BUREAU OF FISHERIES 
air averaged 10° the colder for 10 days in January, 9° the colder at Boothbay, and 
it may be more than 20° colder than the water in the western side of the gulf on the 
coldest days. Thus, on December 21, 1924, when the mean surface temperature of 
the southern side of Massachussetts Bay was about 4.3° (p. 650), the air temperature 
was — 18° C. at Boston (p. 650) . As another example I may cite December 17, 1919, 
when the air temperature was about —21.5° C. at Lubec (7° below zero F.),the 
temperature of the surface water being 0°. 
In the winter of 1919-20 (a cold year) the air temperature averaged about 3.1° 
colder than the surface at Gloucester from December 2 to March 1 and about 5° 
colder than the water at Lubec. At Eastport the United States Army Signal Service 
found the mean water temperature to average about 6.6° warmer than that of the 
air for the period December to February during the 10 years 1878 to 1887. 
The temperatures collected by Rathbun at lighthouses and lightships do not 
cover the months of January or February, and his statement (Rathbun, 1887, p. 
166) that the reason for this omission is “the manifest errors of observation some- 
times made during extremely cold weather” makes it doubtful how close an approx- 
imation to the truth is given by his averages for the last half of December. Conse- 
quently, it is necessary to turn to the observations taken on the Halcyon during 
December to January, 1920-21, for the relationship between the air and surface tem- 
peratures for the open gulf in midwinter; nor do these fairly represent its outer 
waters, all having been taken within 30 to 40 miles of land. 
These Halcyon stations show the air 4.4° colder than the water off Boston Har- 
bor (station 10488), but averaging about 2.5° colder than the water in the northeast- 
ern corner of the gulf and precisely the same as the water in the Fundy Deep 
(station 10499). 
The records for this cruise would have been more fairly representative had it 
included any severely cold days, which it did not, for the obvious reason that when 
icy northwest gales sweep the gulf oceanographic research from a small ship becomes 
impossible. Nevertheless, the regional difference just sketched does illustrate the 
very important fact that the cold winds of winter are most effective as cooling 
agents close in to the land. 
While no exact data are at hand for Georges Bank in early winter, general 
report has it that the temperature of the air is close to that of the water there in 
December and January, except when cold northwest gales blow out from the land 
or warm “southerlies” blow from the tropic water outside the edge of the continent. 
From the oceanographic standpoint, the most instructive conclusion to be drawn 
from the relationship between the temperature of the air and that of the water is 
that the surface of the gulf follows the air in its seasonal changes (p. 699; Bigelow, 
1915 and 1917). This, of course, is a corollary of its situation to leeward of the 
continent, with winds blowing from the land out over the sea for a much greater 
percentage of the time than vice versa, especially in winter. It follows from this, as 
I have emphasized in earlier publications, that the relation of sea climate to air 
climate is, on the whole, the reverse here of what applies to northwestern Europe, 
the surface of the sea responding rapidly in winter to the rigorous air climate. 
How closely the winter temperature of the water of the harbors and bays tributary 
to the gulf depends on the influence of the land is illustrated by the fact that Gloucester 
