NANTUCKET HARBOR AND COATUE 521 



Brant point, and Coatue all represent deposits built up by the sea out of 

 the waste of other portions of the island. The harbor thus formed by 

 Brant point and Coatue is a body of water much protected from the ac- 

 tion of the waves and consequently of value to man. It is, however, a 

 region of comparatively quiet water, and therefore a region where sand 

 may be deposited more easily than in Vineyard sound. If sand is 

 carried in by the tide, there is a tendency to raise the level of the sand 

 flats in the harbor, when more sand is carried in by the rising tide than 

 is carried out by the falling tide. Another source of filling is, of course, 

 the sand brought in by the wind across Coatue. Except in the region of 

 the jetties, no detailed studies have been made of the rate of filling of the 

 harbor. It was supposed that the breaking through of the Haulover 

 might effect a scouring out of the sand in the harbor by forming a tidal 

 current from the head of the harbor to the opening between Brant point 

 and Coatue. It was even proposed* to cut through the tombolo at the 

 head of the harbor in order to increase the tidal scour at the mouth of 

 the harbor. The results of the breaking through of the Haulover show 

 that there was no appreciable effect at the mouth of the harbor from 

 the opening between Coskata and Wauwinet. It was pointed out in the 

 discussion of the forms of the tombolo since the break in the winter of 

 1896-'97 that the tombolo is really continuous below water, and that 

 there never has been any channel across this tombolo deep enough to 

 allow the water to have any force in scouring out the harbor. 



The shoals between Coatue and the northern shore of the oldland are 

 so near to the surface of the water that it would be impossible to get a 

 current of any great erosive force to act south of Coatue without the ex- 

 penditure of a very large sum of money. 



Coatue 



Coatue has been built from the oldland of Coskata island southwest 

 toward the town of Nantucket, and forms a mass of sand 5 miles long, 

 practically all of which must have come from the east side of Nantucket 

 and traveled around Great point along Coskata beach. On the north- 

 west side it has a smooth outline, showing that the dominant current is 

 along the shore. On the southeast side there are six cuspate projections 

 into the harbor, which probably indicate a small eddy current between 

 each pair of points. On nearly all of these points there is at present a 

 little pond, showing that the growth was probably that of a V-shaped 

 bar inclosing a lagoon which has been more or less filled by sand. On 

 the points of some of these forelands the lagoon is completely filled, and 



* Report of the Chief of Engineers, U. S. War Department, 1880, p. 431. 



