590 BULLETIN OF THE BUEEAU OF FISHERIES 



local variation as the tide swirls around the islands and ledges. The maximum tem- 

 peratures at Seguin Island Lighthouse for the years 1881 to 1885 (Rathbun, 1887), 

 were, respectively, 13.3° to 13.9°, 13.3° to 13.9°, 13.9° to 14.4°, 13.9° to 14.4°, and 

 14.4°. This agrees with readings of 13.9° at two localities within a few miles of the 

 island on August 22, 1912, and with 12.8° to 14° in that general neighborhood on July 

 18, 1925; but one need run only a few mUes offshore from this part of the coast to find 

 the surface warmer than 16°, and Doctor Kendall records a reading of 16.7° within 

 about 8 miles of the land oflf Seguin on August 16, 1897. 



The surface temperature rises to 16° to 18° in Boothbay Harbor during the last 

 week of July and the month of August (fig. 30) ; equally high, no doubt, in other 

 sheltered bays in this neighborhood. 



Surface readings taken on a line across the mouth of Penobscot Bay ranged from 

 12.8° to 13.9° on August 21, 1912, while Rathbun (1887) gives maximum tempera- 

 tures of 11.7° to 12.2° at the lighthouse on Matinicus Rock at the western gateway 

 to the bay, where the water may be somewhat chilled by the swirhng tidal currents. 

 The surface in sheltered situations within Penobscot Bay may warm to a tempera- 

 ture several degrees higher than this before autumnal cooling sets in, but infor- 

 mation is scant for this particular region. 



Our surface readings among the outer islands along the coast of Maine, east of 

 Penobscot Bay, and out to the 100-meter contour usually have ranged between 10° 

 and 12° for the last half of July and for the month of August (fig. 47). After a 

 few calm, warm days the temperature of this zone may rise locally to 13° (12.78° 

 off Mount Desert Island, August 13, 1913, station 10099, has been our highest record 

 there). The surface water is considerably warmer up the bays, locally, depending 

 on the topography of the bottom as determining how actively the water is stirred by 

 the tide, and especially on the extent of the flats laid bare to the sun on the ebb. 

 Surface readings of 10.6° to 11.7°, recorded by the Halcyon within a mile or two of 

 Great Duck and Little Duck Islands, Bakers Island, and Long Island on August 8 to 

 11, 1925, cover the usual midsummer range close in to the islands and among them 

 for the Mount Desert region. 



Rathbun (1887) gives maximum summer temperatures of 11.6° to 13.3° at Petit 

 Manan light, and although the surface water off Machias was only 8.9° on July 15, 

 1915 (station 10301), probably it is always as warm as 10°, or warmer, there during 

 the last half of August, and usually 11° to 12°, except where some local upwelling is 

 taking place. 



The hourly temperatures taken off the eastern coast of Maine during the last half 

 of August, 1912, are especially interesting because they suggest a movement of the 

 coldest surface water (colder than 13.5°) offshore (i. e., to the southwest), out past 

 Mount Desert Rock (fig. 47). Unfortunately I can not state whether this phenom- 

 enon is regularly recurrent in summer; but the fact that the surface was slightly 

 cooler (9.3°) near Mount Desert Rock on September 15, 1915, than close in to Mount 

 Desert Island (9.8° to 10.8°), near Petit Manan Island a few rmles eastward along 

 the coast (10.5°), or near Swans Island to the westward (10.8°), suggests that some 

 such distribution of surface temperature is at least not unusual for that general 

 region. 



