GREAT POINT 509 



southern coast is called), but, as we shall see, the conditions at this opening are 

 peculiar. At the ' inlet ' the outer bar represents what is gone from the sandy 

 cordon at the opening, while the inside bar, sometimes called the 'swash,' is the 

 ground-up sand delivered by the breakers to the flood current and dumped at the 

 point where the flood current loses its power in the lagoon. The circus of shoals 

 outside of the Monomoy entrance is an encroachment from an independent source, 

 as the comparative map shows." 



He considered that " the net effect is a westwardly movement," and 

 that it was necessary to study carefully the action along the cliff on the 

 shore and on the bottom in order to settle whether the shoals were in 

 danger of obstructing navigation at this point or not. 



In order to get at any estimate of the time necessary to build these 

 sand spits into one continuous mass of sand, which the writer has named 

 a tombolo,* it is important to study in the greatest detail possible the 

 method of the upbuilding of the sand. Although there may be no im- 

 mediate danger to the commerce of the country at this particular point, 

 there may be places at other points along the coast where the facts ob- 

 tained by the detailed study of the action of the sea along Great point 

 and Monomo3 r will enable engineers to prevent or delay the closing of 

 important waterways. 



As shown by various measurements made by the U. S. Coast and 

 Geodetic Survey along the east side of Nantucket and cape Cod, there 

 has been within the last fifty years a decided cutting back by the sea of 

 the coast line. From L846 to 1887 there has been a retreat of the shore- 

 line between Sankaty head and Great point, increasing in amount from 

 nothing in these two areas to a maximum of 300 feet at Coskata island.f 



While Monomoy J has grown southward in a marked degree, Great 

 point has remained comparatively stable in its position with reference to 

 its distance north from any fixed point in Nantucket island. § There 

 have, however, been decided changes along the shoreline of Great point 

 within the last few years, although the extreme northern extension of 

 Great point is practically the same today as it was fifty years ago. It is 

 possible that the breaking through of the sea at the old Haulover, at the 

 head of the harbor, may have influenced these changes somewhat. This 

 point will be kept in mind in future studies, but at the present time the 

 writer does not wish to express an opinion. 



On the east side of Great point the sea is cutting into the sand which 

 forms Great point. On the west side of Great point there was discovered 

 a building up of the sand a short distance south of Great Point light 



* Shoreline topography, Proc. Am. Acad. Arts and Sciences, vol. xxxiv, 1899, p. 189. 

 f H. L. Marindin : U. S. Coast and Geodetic Survey. Appendix no. 6, 1892, p. 245. 



X H. Mitchell : U. S. Coast and Geodetic Survey. Appendix no. 9, 1873. 



£ H. L. Marindin : U. S. Coast and Geodetic Survey. Appendix no. 6, 1892, p. 244. 



