1891. J NEW YORK ACADEMY OF SCIENCES. 33 



November 30, 1891. 



Stated Meeting. 



Yice-President Dr. Hubbard in the chair. About thirty persons 

 present. 



The minutes of the previous meeting (November 23d) were read 

 and approved. 



The following paper was then read, entitled : 



The Clays of the Hudson River Valley. 



BY HEINRICH RIES, COLUMBIA COLLEGE. 



(Published bt Permission of the N. Y. State Museum.) 



(Illustrated by lantern slides.) 



Summary of Contents. — 1. General description of the clay deposits, with spe- 

 cial reference to lliose at Cornwall and Thiells. Unstratified material covering 

 the clay. — 2. Delta deposits. — 3. Terraces. — 1. Conclusions. — 5. Organic re- 

 mains. — 6. Concretions. — 7. Tables. 



A characteristic topographic feature of the Hudson River Yalley 

 between New York and Albany is formed by the natural terraces 

 which extend more or less continuously along both sides of the 

 river. 



These terraces are underlain by three types of quaternary de- 

 posits : — 



1. Drift. 



2. Delta deposits. 



3. Estuary deposits of fine stratified sand, and blue and buff clays. 

 These estuary deposits indicate a period of submergence, during 



which the water covering the land was very quiet. 



The clays extend more or less continuously from Sing Sing to 

 Albany, with the exception of two narrow portions of the river, 

 viz., from Jones's Point to Cornwall and from New Hamburgh to 

 Staatsburgh, where little or no clay is found, the terrace, if present, 

 being usually underlain by till. BeloAv Sing Sing the clay occurs 

 in isolated patches of no great extent. ( W. W. Mather, Geol. First 

 District, N. Y., p. 133.) 



The different members of the estuary deposits are not always 

 present in any one spot. Sometimes only two occur, rarely only 

 one. The clay is usually horizontal, but in a few instances dips 

 slightly towards the river; the stratification is more distinct and 

 the layers thinner in the buff c[?i\. The blue is more plastic than 

 the buff and makes a better brick. Both effervesce readily with acid 

 from the amount of lime in them and are known as marly clays. 



At most localities where the clay is exposed the blue has a greater 

 thickness than the buff, though there are cases in which only the 

 buff is present. 

 Vol. XI.— 3 



