1891.] NEW YORK ACADEMY OF SCIENCES. 35 



I am inclined to think that the disturbance at this locality was pro- 

 duced by one or more land-slips. 



At Cornwall the upper terrace is underlain by till, and this we 

 find to be the usual succession. In only two instances was the 

 upper terrace found to have the clay beneath. 



Going further down the river we come to llaverstraw. Here we 

 find three terraces, the upper one underlain by till containing large 

 boulders; this drift dips under the clay, as can be seen by a section 

 exposed at the south end of the village and to the rear of T. Chrys- 

 tie's yard. 



Some two miles west of Haverstraw along the N. J. & N. Y. R. 

 K. between Thiells and Mt. Ivy is a very interesting little basin- 

 shaped clay deposit of elliptical outline. It is not over 18 feet thick, 

 as determined by boring. The clay is underlain by till and over- 

 lain by two to three feet of the same material containing small ice- 

 .scratched boulders. The valley in which this deposit lies contains 

 numerous ridges of drift, whose longer axes lie parallel to the 

 direction of the valley. A section of one of them is exposed near 

 the clay deposit. This latter was probably formed in a small tem- 

 porary lake under the ice. 



At Stony Point the upper surface of the clay is very uneven and 

 is covered by two to eight feet of unstratified material consisting of 

 coarse sand and cobblestones. A similar deposit is found over- 

 lying the clay at Low Point above Fishkill. Also at Dutchess 

 Junction the clay is covered by the same kind of material, this latter 

 locality being the only one where any stratification is observable in 

 the mass. The layers dip towards the river. 



The delta deposits of the streams tributary to the Hudson are of 

 great interest. They afford us an idea of the former size of these 

 streams, and also indicate the amount of submergence which took 

 place at the several points. 



These delta deposits are made up of two members : 1st, the thinly 

 stratified loamy clays which were deposited a short distance from 

 the mouth of the river ; and, 2d, the coarse, cros.s-bedded sands and 

 gravels which were deposited at its mouth. 



The following streams between New York and Albany have 

 formed delta deposits (as noted by Dr. Merrill, Amer. Journ. Sci., 

 June, 1891) : Wappinger's Creek, IS^ew Hamburgh ; Fishkill Creek ; 

 Quassaic Creek, Newburgh ; Moodna River, Cornwall ; Indian 

 Creek, Cold Spring; Peekskill ; Pocantico River, Tarrytown ; Saw- 

 mill River, Yonkers; Tibbitt's Brook, Van Cortlandt ; Minisceongo 

 Creek, Haverstraw. 



All of these deltas have been largely eroded by the streams which 

 formed them, and little is left of them at the present day. 



Dr. Merrill (Amer. Journ. Sci., June, 1891) considers it highly 

 probable that some of these deltas once filled a large portion of the 

 valley in the Highlands. At Jones's Point opposite Peekskill there 

 is a deposit of thinly stratified loamy clay which may have formed 

 a portion of the secondary cone of Peekskill Delta ; also at Rose- 



