PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 
865 
Analysis of these sets shows a dominant drift toward the north and west (aver- 
age direction about NW. by W.) during the spring, summer, and early autumn, 
averaging about 3.4 miles per day; but about as strong a southeasterly set (3 miles 
daily) during the late autumn, winter, and early spring, averaging about S. 50° E. in 
direction. If January and February be credited with about the same dominant 
drift as is recorded for December and March, the average set of water for the year 
works out at about 1.3 miles per day toward the N. 74° W. The rate has aver- 
aged lowest (less than 0.1 knot) from March through June, and drifts as strong as 
0.2 knot have been recorded only during the months from August to December, a 
fact of some interest in connection with the discharge of surface water from the gulf 
(p. 974). This series of observations gives evidence of a considerable balance of 
movement of water toward the WNW. past the southern slopes of Nantucket Shoals, 
and whether the set be in that direction or toward the southeast, it is away from 
the gulf in either case. 
This seasonal reversal in the direction of the dominant current is probably 
caused by the wind, with the southeasterly drift of winter reflecting the prevalence 
of strong northwest winds at that season ; but the fact that the summer drift toward 
the west or northwest is not parallel with the prevailing southerly and southwesterly 
winds, but at right angles to them, reveals the dominant tendency for the water here 
to move westward. 
Current measurements taken at eight stations along the southern rim of the 
the Gulf of Maine by the United States Coast and Geodetic Survey in 1877 show 
in each case a considerable nontidal resultant; and the indicated drift at any one of 
these may have been affected by the wind, for all were of short duration. However, 
they prove so consistent with the theoretic expectation of a clockwise movement 
around a shoal (p. 972) that they are probably representative of the prevalent sum- 
mer state. The resultant drifts, as calculated by Mitchell (1881, p. 189, table 8), 
are as follows: 
Sta- 
tion 
Latitude 
Longi- 
tude 
Region 
Directions 
Velocity 
per 24 
hours 1 
1 
o r 
41 10 
O / 
68 55 
South Channel 
N. 31° E 
Miles 
4.5 
2 
41 21 
68 23 
Northwest slope of Georges Bank 
N. 79° E2 
5.7 
3 
41 31 
67 52 
West side of Georges Shoa!s__ 
N. 70° W ■ 
2.8 
4 
41 36 
67 24 
East side of Georges Shoals__ 
S. 14° E 
3.5 
5 
41 56 
66 28 
East end of Georges Bank . 
S. 42° E 
3.7 
6 
42 25 
66 08 
Eastern Channel 
S. 76° W? 
6.0 
6 
42 25 
66 08 
Do 
N. 51° W 
10.7 
7 
42 50 
65 56 
South side of Northern Channel _ 
S. 51° E. 
7.3 
8 
43 04 
65 41 
North side of Northern Channel 
S. 59° W 
4.7 
■ The U. S. Coast and Geodetic Survey writes that “resultant,” in Mitchell’s (1881, p. 189) original account, refers to the 
set for a tidal day of 24 hours and 50 minutes. This is reduced here to the set per 24 hours. 
■ The dominant drift is given as southeasterly at station 2, northeasterly at station 3, by Harris (1907, chart 7), and in the 
1912 edition of the Coast Pilot (1912, chart to face p. 9); but a fresh calculation of the nontidal set at these stations by the 
Coast and Geodetic Survey shows a very good agreement with Mitchell’s results. 
These drifts indicate a general movement of the water northwestward around 
the western side of Georges Bank and southeastward over the eastern side, which is 
corroborated by bottle drifts (figs. 174, 176). They also suggest a subsidiary clockwise 
