1890.] NEW YORK ACADEMY OF SCIENCES. 79 



the southeast,, on a portion of which the town of Freehold 

 stands, about 180 feet above tide. 



The estuary deposits of the Hudson River at New York 

 indicate a post-glacial depression of more than 70 feet. In the 

 basin between the Palisade ridge and the Orange Mountain, 

 similar estuarine conditions prevailed, and the streams which 

 flowed into that estuary formed delta-plains in water which stood 

 about 80 feet higher than present tide-level. 



The altitudes of the Hudson River estuary deposits have been 

 determined at a few points as follows: — 



Fort Lee, N. J 70 feet 



Mouth of Croton River 100 " 



Peekskill 120 '' 



West Point 180 " 



Fishkill 210 " 



Vicinity of Albany 335 *' 



A preliminary study of these formations, in connection with 

 those of similar origin in New Jersey, indicates that -the lines 

 of equal terrace altitude are nearly parallel to the Kittatinny- 

 Shawangunk mountain range, and suggests that the elevation of 

 these estuary deposits to their present height may be due to a 

 change of altitude and attitude in the continental margin, 

 caused by an uplift in the Appalachian system. 



On the Long Island Sound shore of Westchester County, N. Y., 

 the till which covers the metamorphic rocks has apparently 

 been levelled off by wave-action at an altitude of 75 to 85 feet. 

 Plains of this character occur at frequent intervals, being 

 separated by river- valleys, and may have been formed during the 

 post-glacial depression which occasioned the estuary deposits of 

 the Hudson River valley. On one of the most extensive of them 

 the village of New Rochelle has been built. 



On Staten Island and western Long Island alluvial plains of 

 stratified material rise gently from the ocean to the margin of 

 the moraine, terminating at an altitude of about 80 feet, and, 

 though no continuous shore-line has been found, these plains 

 are referred provisionally to the same period as the estuary 

 deposits a few miles north. 



The 80-foot depression at the mouth of the Hudson River is 

 believed by the writer to have been contemporary with one of 

 equal amount at Trenton, evidenced there by distinct terraces 

 which, however, have been considered by Mr. W. J. McGee to 

 be of pre-glacial origin. 



In studying the terraces of the Atlantic coast of New Jersey 

 and of the shores of the Delaware estuary and bay, it was found 

 that the principal Quaternary terraces were higher on the bay 



