450 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



highest elevation should be found about the middle of the island. In 

 fact, however, this elevation, about 100 feet, is found at Sankaty Head, 

 its most projecting point, and hence we conclude that in former times 

 the island has extended over a part of the ground now occupied by the 

 shoals. The southern coast of the island, that west of Sankaty Head, 

 has received its shape from the flood current, whilst the west coast, or 

 that north of Sankaty Head, has been formed by the ebb current. 



George's Bank. — The existence of this bank must have been known 

 to the earliest navigators; it was originally called Malebarre. Bank, but 

 lias borne its present name since about 1700. The total absence of cre- 

 taceous and tertiary deposits from the eastern coast of Massachusetts 

 and the coast of New Hampshire leads Professor Hitchcock to the con- 

 elusion that during those ages these coasts must have occupied a higher 

 level than at present; hence it is possible that a greater or lesser part 

 of George's Shoal may once have been dry land. However that might 

 have been, there is not the least doubt from an examination of the sur- 

 face deposit that the bank owes its present shape and height to a thick 

 layer of drift material belonging to the glacial period. Indeed, it is not 

 possible to suppose that masses of ice, many thousands of feet in height, 

 would have finally melted before coming into contact with the warm 

 waters of the Gulf Stream off the southern edge of George's Bank. 

 Hence we may consider this bank as the terminal moraine of the gla- 

 ciers belonging to the glacial period and subsequent to it. Between 

 this bank and the coast of Maine there exists a relation very similar to 

 that between the southern and northern shores of the Great Lakes, and 

 it would require an elevation of less than 1,000 feet to convert the Gulf 

 of Maine into an inland sea. 



The shoalest parts of this bank, George's Shoal and Cultivator Shoal, 

 have less than three fathoms and must be considered dangerous to 

 navigation. From the fact that these shoals conform in their directions 

 to the tidal currents which run across the bank at nearly a right angle 

 to its general stretch, and maintain their shape and position in spite of 

 their exposed location, we are justified in considering them as the per- 

 manent result of tidal action. 



Cape Cod. — Cape Cod is an immense heap of drift material. Its 

 topographical configuration alone shows that, like Nantucket, it has re- 

 ceived great abrasion on its eastern side. The greatest height, about 

 200 feet, exists at the Highlands — the most exposed position, where 

 there has been the greatest wear. The tidal currents, which in this 

 abrasion process w T e must consider the most persistent if not the most 

 active, run parallel to the coast, the flood from the south and the ebb 

 from the north. 



Stillwagen's Bank.— This shoal, discovered by the Coast Survey 

 in 1854, lies across the entrance of Massachusetts Bay in a line from 

 Cape Cod to Cape Ann. There is very little doubt in my mind that 

 this bank belongs to the same geological formation as Cape Cod ; that 

 it formerly was probably much shoaler and directly continuous to Cape 



