82 



CAPE COD GEOLOGY 



The chart makes "Webb Island" coincide with the long bar of Monomoy. 

 There are other reasons for supposing that "Webb Island" lay southeast of 

 Chatham, where the modern chart shows a small shoal with 4 fathoms of water. 

 No trace of this shoal is seen on the map published in 1717. Indeed, it is stated 

 in local histories that the island disappeared before 1700. 



At what appears to be the south end of the Monomoy hook the map places 

 "the Seal island sunken channel way," probably pointing to changes in that 

 vicinity involving the disappearance of former islands of glacial drift. 



The greatest changes appear to have taken place in the neighborhood of 

 Tuckernuck and of Muskeget shoal. Four small islands are represented off the 

 west end of Nantucket where now only Tuckernuck Island, some shifting shoals, 

 Muskeget, and the Gravelly Islands appear above the sea. The soundings on 

 other shoals south of Nantucket given on the map do not accord with the present 

 soundings, which uniformly show greater depth of water. Marthas Vineyard is 

 too grossly drawn on the map to warrant comment; but No Mans Land and 

 the bouldery bar connecting it with Gay Head are shown with considerable 

 accuracy. Cuttyhunk and Nashawena are represented as a single island. There 

 is some reason for believing that in Gosnold's time the islands were tied together 

 by barrier beaches that closed the existing Canapitsit Channel. Block Island 

 is rudely sketched on this ancient chart. For nearly a century no better chart 

 of the coast was brought out. What appear to be copies of this map were pub- 

 lished in the British Coast Pilot and were used by the British navy prior to the 

 American War of Independence. 1 



A few centuries ago the eastern coast of Cape Cod must have been very 

 different in outline and position from what it is now, for it has been straightened 

 out by the cutting back of headlands and the building out along shore of the 

 winged beaches and hooks that terminate the Cape at Monomoy and Province- 

 town. Davis 2 has attempted to restore the old form of this part of the coast. 

 According to his interpretation the innermost, oldest bar at Provincetown 3 

 may have been formed when the land on the south, between Truro and Wellfleet, 



1 The English Pilot, the fourth book, London, 1775. Copy in Congressional Library at Washington 

 contains (No. 8) "A map of the coast of New England from Staten Island to the Island of Breton, as it 

 was actually surveyed by Capt. Cyprian Southack." See Phillips, A list of geographical atlases, 1, pp. 

 590-591, Washington, 1909, which contains references to early maps of the New England coast in earlier 

 editions of The English Pilot. 



2 Davis, W. M., The outline of Cape Cod, Proc. Amer. Acad. Arts and Sci., 33, pp. 303-332, 1896. 

 See fig. 1, p. 311. 



3 At Provincetown in 1916 Dr. T. W. Vaughan called my attention to coarse gravels on the bar at 

 Wood End and Long Point, which indicate the former existence there of a shoal, possibly first an island, 

 of glacial material that has been washed away. 



