PHYSICAL OCEAN OGRAPHY OF THE GULF OF MAINE 
671 
Difference between surface and air temperatures (° C.) 
[— signifies that the air was colder, + that it was the warmer] 
Hour 
Differ- 
ence 
Hour 
Differ- 
ence 
August 15: 
August 15— Continued. 
+2.8 
2 p.m. __ 
+5. 6 
+ 1. 7 
3 p.m. . 
+3. 9 
+ 1. 1 
4 p.m ... 
+ 4.4 
+ 1. 7 
5 p.m. 
+2. 2 
-0. 6 
6 p.m. 
+ 2.2 
— 0. 6 
7 p.m. 
+ 2. 2 
+0. 6 
8 p.m. 
+ 2. 2 
+ 1. 1 
9p.m. 
-1. 1 
+2.8 
10 p.m 
-1. 7 
+2.8 
11 p.m. . 
-1. 7 
+2. 8 
0.0 
+3. 3 
August 16: 1 a.m 
0.0 
1 p.m. - 
+ 5.0 
It is to be noted that while the air temperature did not fall below that of the 
water until between 3 and 4 a. m. on the first night, this happened at 9 p. m. on 
the second. 
In 1920 the air averaged colder than the water in the harbors of Gloucester, 
Boothbay, and Lubec after about the middle of October. According to the temper- 
atures collected by Rathbun (1887), the surface was colder than the air at the 
several lighthouses after the following approximate dates of 1881 to 1883: 
Locality 
Pollock Rip 
Thatchers Island 
Boon Island 
Seguin Island 
Matinicus Rock 
Mount Desert Rock 
Petit Manan 
Year Date 
After Nov. 16. 
After Nov. 1. 
After Nov. 8. 
Between Nov. 11 and 16. 
After Oct. 30. 
After Nov. 1. 
After Nov. 6. 
After Nov. 1. 
After Oct. 25. 
Nov. 1 to 6. 
After Oct. 17. 
After Oct. 25. 
Nov. 1 to 6. 
After Nov. 16, but with reversals. 
After Nov. 16. 
After Nov. 6. 
After Nov. 8. 
After Oct. 22. 
After Nov. 26. 
Thus the water in the coastal belt is constantly warmer than the air after the 
last week of October or the first week in November. From that time on the differ- 
ence between air and water increases until the middle of January, when the air 
averages about as much colder than the water as it is warmer in summer (illustrated 
by the 10-day averages for Gloucester, Boothbay, and Lubec, figs. 29 to 31). During 
periods of extreme cold, such as come to New England and to the Maritime Prov- 
inces almost every winter, the spread between air and surface temperatures is even 
wider than the spread of the reverse order in summer. At Lubec, for example, the 
