1891. | NEW YORK ACADEMY OF SCIENCES. 33 
November 30, 1891. 
STATED MEETING. 
Vice-President Dr. Hupsarp 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 By 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 those at Cornwall and Thiells. Unstratified material covering 
the clay.—2. Delta deposits.—3. Terraces:—4. Conclusions.—5. Organic re- 
mains.—6. Concretions.—7. Tables. 
A characteristic topographic feature of the Hudson River Valley 
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. Below 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 clay. 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. 
Vou. XI.—3 
