Geology of Long Island. 341 



XX. — On the Geology of Long Island. 



BY F. J. H. MERRILL. 

 Read November 7, 1884. 



The following contributions to the Geology of Long Island are 

 the result of some five weeks' exploration and study of that well- 

 known and interesting region, during the summer of 1883. This 

 paper is but preliminary ; and many questions which have been 

 merely touched upon or wholly neglected, the writer hopes to 

 discuss at length when more extended research and deeper exca- 

 vations have given him further data. 



The surface geology of this region has already been minutely 

 described by Mather in his Report on the Geology of the First 

 District of New York, 1843, and also, with special reference to 

 the glacial deposits, by Mr. Warren Upham, in his articles on 

 "Terminal Moraines of the North American Ice Sheet," Am. 

 Jour. Sci., Ill, 18. I shall therefore review very briefly the 

 physical characteristics of the island and endeavor to throw what 

 additional light I can upon its geological history, from the study 

 of sections of strata recently exposed, and such other phenomena 

 as it has been my fortune to observe. 



Long Island as a whole is comparatively low and flat, but 

 throughout the central part is a range of hills extending from 

 Bay Ridge northeasterly to Roslyn, and thence continuing to 

 Montauk Point in a series of elevations, the more important of 

 which are known as West, Dix, Comae, Bald, and Shinnecock 

 Hills. The average height of this chain is about 250 feet ; but 

 at some points it is much greater. Harbor Hill at Roslyn is 384 

 feet above tide ; Jane's Hill is 383 feet high ; Reuland's Hill has 

 an elevation of 340 feet, and Wheatly Hill is 369 feet above the 

 sea. 



There is also, along the north shore, an elevation which usually 

 follows the contour of the numerous deep bays and inlets, vary- 

 ing in night from 30 to 200 feet, and almost continuous from 



