199 
Also in front of the Harbor Hill Moraine is an extensive, 
though rather thin, cover of fine gravel and sand deposited by 
water flowing from the melting ice. In the northern part of the 
Botanic Garden, close to the moraine, the fine gravel contains 
boulders. South of Brooklyn this so called wash plain extends 
down to the bays north of Coney Island. It is fan-shaped in out- 
line with the handle near the Botanic Garden, where the main 
streain issuing from the ice had its mouth. 
The length of time that the ice border remained at the two 
moraines is not known. Nor is the time occupied by the recession 
— 
from the first moraine to beyond the second known. However, 
if we may judge from other moraines, whose rate of formation 
has been determined it seems probable that each moraine repre- 
Fic. 20. Glacial sand plain with intercalated till bed near the top. West 
side of Hempstead Harbor, Long Island. The glacial boulders were prob- 
b ropped from floating icebergs while the sand and till were being 
deposited. The talus (Latin, ankle) over the foot of the embankment has 
been deposited as a series of alluvial fans. (7989. From Barton W. Stone 
Collection, Columbia University. Courtesy of Prof. A. K. Lobeck.) 
