PHYSICAL OCEANOGRAPHY OP THE GULF OF MAINE 575 
succession illustrated by these two stations is characteristic of that side of the basin 
in general. 
No observations have been taken in the western side of the gulf in June, or on 
Nantucket Shoals, on the cruises of the Bureau of Fisheries’ vessels, except those 
just mentioned; but the daily data tabulated by Rathbun(1887) for several lighthouses 
and lightships partially fill the gap for the coast sector between Cape Ann and the 
Mount Desert region, and are consistent with the serials taken of late years in the 
northeastern part of the gulf, in the Bay of Fundy, and in Massachusetts Bay. 
Approximate temperatures (°C.) at the surface on June 16, from Rathbun’s (1887) tables 1 
Locality 
1881 
1882 
1883 
1884 
1885 
Average 
Pollock Rip lightship 
14.2 
9.7 
12.2 
11.7 
10.6 
11.7 
13. 2 
12. 2 
12. 7 
10 
8.3 
10.6 
11.4 
10.3 
10. 1 
9.8 
10.9 
11.9 
11.4 
9.4 
10. 7 
8.3 
8.3 
7.2 
8.3 
7.5 
7. 9 
7.6 
8.9 
10.3 
10.6 
10. 1 
9.6 
1 Given only to nearest 0.1 °. 
The 10-day averages for Gloucester and Boothbay for 1920 (figs. 29 and 30) 
show that the water warms only slightly faster in inclosed locations of this sort than 
off the open coast (compare 13° at Gloucester and about 12° at Boothbay on June 
15 with Rathbun’s record of 12° to 13° at Thatchers Island, off Cape Ann, and of 9° 
to 11° at Seguin Island. A temperature about 3 degrees lower at Matinicus Rock, 
at the mouth of Penobscot Bay, than at Seguin Island, some 34 miles along the 
coast to the westward, probably reflects some local retardation of vernal warming 
by the spring freshets from the Penobscot River. Conversely, the comparatively 
high temperature at Petit Manan suggests that readings as warm as 10° are to be 
expected by June 15 after a few days of warm weather, in sheltered locations along 
shore in shallow water, to the east as well as west of Mount Desert. In fact, Doctor 
McMurrich records almost as high surface temperatures (9° to 9.5°) at St. Andrews 
by June 15 in 1916. Lubec Narrows, however, open to the Grand Manan Channel 
and with a great volume of water rushing through on every tide, had warmed to 
only about 6° by this date in 1920 (fig. 31). 
Earlier in the season, and up to mid May, the vertical distribution of tempera- 
ture in the upper 150 meters or so is of one type throughout the inner waters of the 
gulf, though the actual values differ slightly from station to station. During late 
May and June, however, very important differences develop between the state just 
described for the western side of the gulf (where the rapid warming of the upper 
stratum by the sun, coupled with the sudden establishment of a high degree of 
vertical stability, causes the development of a steep temperature gradient in the 
upper 40 to 50 meters, overlying water more nearly homogeneous) and the north- 
eastern part of the gulf, where more active stirring by the tides spreads the warmth 
received from the sun through a thicker stratum of water. Furthermore, we find 
the rate of warming decreasing from west to east as we follow around the coast fine 
of the gulf, even after this regional difference in the downward dispersal of the heat 
received has been allowed for. Thus, the surface had warmed only from 5° on May 
