110 



CAPE COD GEOLOGY 



ARTIFICIAL CHANGES 



CHANGES MADE BY WHITE MEN 



The geological map of the densely built-over part of the town of Nantucket 

 is necessarily imperfect. Low, marshy ground that originally bordered the shore 

 of the harbor has been filled, and high ground has been leveled down. The 

 names of North and South Water Streets indicate that they were laid out along 

 the shore, the land east of them having been gained by filling in along and be- 

 yond the ancient beach. Gull Island, the site of the brick-clay pits referred 

 to in historical accounts, is not now an island. Everywhere glacial boulders have 

 disappeared. Wesko, the aboriginal name of the site of Sherburn, now Nan- 

 tucket, is said to mean ' 'white stone," presumably a light-colored boulder that 

 stood on the site. The account given by the author of ' 'The Letters of an Am- 

 erican Farmer," 1 indicates that small boulders and "stones" were never so 

 abundant on the morainal north side of the island as they still are on parts of 

 Marthas Vineyard and on the neighboring mainland. According to the writer of 

 these letters stones were brought from the mainland both for filling in about the 

 wharves and for building cellar walls. 



INDIAN SHELL HEAPS 



Some heaps of fragments of shells left by the aborigines are found along the 

 coast. Scant traces of these relics of the native inhabitants have been seen at 

 several places along the east coast, at the top of the glacial drift beds and 

 beneath a later coating of wind-blown sand. A deposit of shells covered by 

 peat was seen in the low cliffs at Squam Head. 



In 1915 layers of shells were well exposed in the low bluff on the south side 

 of Coskata islet, at the north end of Haulover Break. The stratification in these 

 layers indicates a change in the species gathered, if not in the local geographic 

 conditions, while the shells were collected. The deposit begins on the east with 

 a zone about 2 inches thick made up entirely of shells of Venus mercenaria. 

 Upon this layer lie 2 to 3 inches of wind-blown sand, over which there is another 

 thin layer of shells, chiefly of Ostrea sp., and a few Venus mercenaria, all of 

 which is covered by old wind-blown sand and turf. A few feet west of this place 

 a layer of Venus mercenaria about 6 inches thick begins the record, upon which 

 lies a few shells of Ostrea. The whole deposit does not exceed 10 inches in thick- 

 ness and is covered by later wind-blown sand. The change from the clam (Venus 

 mercenaria) to the oyster (Ostrea sp.) is well marked in this deposit. The deposit 



1 Crevecoeur, Hector St. John, The letters of an American farmer, pp. 97-98, Philadelphia, March 4, 



1793. 



