PHYSICAL OCEAXOGEAPHY OF THE GULF OF MAINE 519 



and the mountains of Mount Desert (with the maximum elevation of 1,500 odd feet) 

 are exceptions to this rule, while the cliffs of the north shore of Grand Manan rise to 

 a height of 200 to 300 feet, almost sheer from the water. 



DEPTH OF THE GULF^ 



If we take the 50-fathom (virtually the 100-meter) contour as marking the con- 

 fines between the peripheral and central parts of the gulf (a natural boundary, because 

 this level not only outlines the northern slope of Georges Bank but includes virtually 

 all the outlying islands), the coastal shallows to the east, north, and west and the 

 rim on the south inclose a bottle-necked basin that communicates with the open sea 

 by two narrow channels only — the eastern and northern. The Eastern Channel, at 

 its narrowest point between Georges and Browns Banks, is about 140 fathoms (256 

 meters) deep along its trough; the Northern Channel is 65 to 80 fathoms (120 to 145 

 meters) , with a maximum of 78 fathoms (143 meters) in the narrows between Browns 

 Bank and the Coast Bank. North of the rim the deepest water (100 fathoms, or 200 

 meters and over) takes roughly the form of a Y, with its two arms extending west- 

 ward and northeastward. As these two troughs apparently were xmnamed, I have 

 christened them the "western" and "eastern" basins. They join in the southeast 

 corner of the gulf, where they are continuous with the Eastern Channel. As Mitchell 

 (1881) has pointed out, more than 10,000 square miles of the gulf are deeper than 100 

 fathoms. The gulf is deepest just inside the entrance to the Eastern Channel and 

 close to the northern slope of Georges Bank as a trough some 50 miles long (west 

 and east), with 150 fathoms (275 meters) or more, and a maximum of 184 fathoms 

 (336 meters). There is also a second, smaller bowl, deeper than 150 fathoms (180 

 fathoms, or 329 meters, maximum) in the inner part of the western branch of the Y, 

 off Cape Ann. 



Over the south-central region of the gulf (that is, the region of union of the two 

 arms of the basin) the depth is generally from 100 to 120 fathoms (180 to 220 meters) , 

 varied, however, by many shoaler spots of 90 to 100 fathoms and by occasional 

 deeper soundings of 120 to 135 fathoms (220 to 250 meters). The configuration of 

 the bottom makes the fathom a more instructive basis for contour lines than the 

 meter in just this region; for whereas the 100-fathom curve includes the whole basin, 

 the 200-meter contour, though differing so little in actual depth, is much interrupted 

 here by ridges of 180 to 190 meters, obscuring the essential troughlike conformation 

 of the basin. In the western arm of the basin the water is deepest 45 miles east of 

 Cape Ann; in the eastern arm it is deepest in the extreme northeast corner (145 

 fathoms, or 265 meters). In both branches the general level of the basin floor is 

 from 115 to 130 fathoms (210 to 238 meters). 



BANKS AND SINKS 



Isolated sinks or pot holes are numerous; indeed, the deeps of the two basins 

 just mentioned are such. Most of these do not faU deep enough below the sur- 

 rounding bottom to call for any special comment, but three such bowls are so deep 



s On theordinarynavigationalchartsof the region, published by the United States Coast and Geodetic Surveyand the United 

 States Hydrographic OfBce, the depths are given in fathoms. Consequently, the following discussion is also in fathoms, but 

 with the equivalents in meters also stated. 



