BULLETIN OF THE UNITED STATES FISH COMMISSION. 453 



most exposed position of any island on the coast of Maine. Its pres- 

 ervation through the glacial period in nst be ascribed partly to the 

 harduess of its mineral composition, and partly to its position in the 

 rear of Mount Desert Island, with which it is connected by a ridge, at 

 a depth of about 80 fathoms. 



Grand Manan Island. — This island, which rises to the height of 

 about 400 feet, lies in the middle of the entrance to the Bay of Fundy. 

 It belongs, politically, to the Province of New Brunswick, but, in its topo 

 graphical and geological structure, it resembles more closely Maine, 

 from Avhich it is separated by a channel of rather less than 40 fathoms. 

 It even appears probable that, during the earlier parts of the glacial 

 period, this island formed a part of the coast of Maine. 



Oashe's Ledge. — Cashe's Ledge is a rock with 5 fathoms of water 

 on it. Situated near the middle of the gulf, it constitutes the only 

 danger in the deeper waters of the gulf, aud inside of George's Bank. 

 Cashe's Ledge and Ammen's Rock are identical, although two rocks 

 are indicated on the Coast Survey charts. This doubling a single rock 

 is owing to uncertainty of position, and is in accordance with the maxim 

 that it is safer, in cases of doubt, to give one more rock than really 

 exists, rather than omit one. Cashe's Ledge forms the crest of the 

 middle one of three submarine ridges, which probably consist of granite 

 and show, by their shapes, that they have been subjected to strong 

 glacial abrasion. It is not improbable that these rocks may have been 

 above water in antediluvial times. 



Platt's Bank. — The existence of this bank was known to fishermen 

 before its discovery and survey by Captain Piatt, of the Coast Survey 

 It is situated upon the same rocky plateau with Cashe's Ledge, Jeffrey's 

 Bank, and the Fippeunies. It has 29 fathoms' depth, whilst Jeffrey's' 

 Bank and the Fippeunies, the existence of which has been generally 

 known much longer, have a depth of 46 and 39 fathoms, respectively. 

 None of these ledges have much importance, either to navigation or as 

 fishing grounds, aud their shapes have not been as well determined, by 

 survey, as the ledges previously mentioned. Hence we will not venture 

 upon any hypothesis regarding their geological structure, beyond the 

 statement that they must be composed of some hard material, since 

 they occupy positions where they must have been subjected to strong 

 glacial abrasion. 



Gulf of Maine — General Discussion. — We may fairly assume 

 the whole of the Gulf of Maine, from the foot of the fiords to George's 

 Bank, to be strewed over with bowlders, and the debris of melted gla- 

 ciers and icebergs; but all this, in the deeper parts of the gulf, is hid- 

 den under a heavy layer of mud. The greatest depth in the gulf is 

 about 180 fathoms, and this depth is reached in both basins, the one to 

 the eastward and the oue to the westward of Cashe's Ledge. This 

 depth is rather insignificant, when compared with the depths outside 

 of the banks, where, at a distance of only 20 miles, 1,500 fathoms are 

 rached. 



