Dana — Long Island Sound in the Quaternary Era. 429 



in 1877.* These bays are marvels for size and depth, consid- 

 ering that they have now no sufficient stream to make or keep 

 them open. Their varying courses and complexity of form are 

 unfavorable to the idea that they were made by the shove of 

 the glacier against the unconsolidated sand, gravel and clay- 

 beds of the island — an idea suggested by Mr. F. J. H. Merrill. f 

 The great bay east of Eaton's Neck, called Huntington Bay, 

 has a depth of 50 feet in its southwest part, and of 52 and 58 

 feet in its inner eastern section called Northport Bay. The 

 bay west of Lloyd's Neck, called Oyster Bay, has a depth, just 

 south of the sand-bank that nearly closes its entrance, of 63 

 feet, and the inner western portion has soundings of about 50 

 feet. These equal the greatest depth in New York harbor. 

 The narrow Hempstead Harbor, farther west, has a depth of 

 30 feet almost at its inner extremity. The depths of these 

 bays have been diminishing since glacial times by the west- 

 ward tidal drift, which has made shallow entrances, and by the 

 transporting action of waters draining the high sand and gravel 

 hills which border the bay. The most probable explanation 

 of so great size and depth, and of so complex forms for these 

 essentially riverless bays, is that of their excavation by under- 

 glacier streams when the island was enough higher to give the 

 streams the power of cutting ; and of cutting not only 50 and 

 60 feet below the present surface but 60 plus the amount of 

 depth lost by subsequent depositions. An increase in height 

 of 100 feet seems therefore to be a reasonable conclusion. 



But if the northern side bears such evidence of elevation, the 

 southern should afford some corresponding facts. We find 

 such apparently in the south side gravel plain and that at the 

 head of Peconic Bay. This south-side plain is two-thirds as 

 long as the island and nearly half as broad. To the north of a 

 middle east-west line — which is shown on the map, between 

 Jamaica on the west and Shinecock Bay on the east — the land 

 rises to 200 feet and beyond, reaching 384 feet in the most 

 elevated part ; and this higher land continues to the northern 

 coast, where the height is mostly 100 to 200 feet ; and also 

 westward to Bay Ridge on the northwest coast of the island, 

 on New York Harbor and eastward to Montauk Point, the 

 southeastern cape. 



These higher lands have a basis of Cretaceous or Tertiary 

 clays and other strata, which, in some places on the north side 

 of the island, have a height above tide-level of 100 feet or more. 

 But the surface is everywhere, though often quite sparsely, 



* Water Courses on Long Island, this Journal, III, xiii, 142. 



My own study of Long Island was made in 1875, 1876, and at that time I 

 reached the conclusions here presented. 



f Annals K T. Acad. Sci., iii, 341, 1886: a valuable paper "on the Geology 

 of Long Island." 



