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i 
86 W. Upham—Terminal Moraines 
hills on Long Island is at the low tract of recent beach-sand 
and marsh called Napeague, four or five miles in length and 
nearly two in width; beyond which are the pastured uplands 
of Montauk, extending ten miles, with depressions to sea-level 
at Fort and Great Ponds. 
The cliffs on the south shore of Montauk, twenty to one hun- 
dred feet high, are constantly undermined by the sea and pre- 
sent fine sections, composed of stratified gravel, sand and dag. 
the latter usually containing intermixed gravel, while in most 
portions of all these beds occasional and sometimes frequent 
bowlders, up to three or more rarely five to ten feet in diame- 
ter, are em ed. No unstratified deposits were found in an 
examination of these cliffs for nearly seven miles, from Fort 
Pond to the light-house. The contour of this peninsula is very 
irregular, with many small ponds and swamps. Its surface is 
everywhere strown with bowlders, often very abundantly, so 
that they nearly cover the ground. These, however, very 
rarely exceed ten feet in diameter, being of small size as com- 
pared with the enormous blocks which are found occasionally 
near the north side of the island. 
hese accumulations of drift, reaching in an essentially con- 
tinuous series of hills nearly 200 miles, from Delaware River 
to Montauk Point, and lying as already stated at the southern 
limit of glacial action, seem to be terminal deposits dumped at 
the margin of the ice-sheet during its period of greatest extent. 
The striated summits of all the mountains of New England, 
New York and northern New Jersey, show that the glacial 
mantle was at least a mile thick at a distance of 200 miles 
north from its southern edge. Its formation from the annual 
excess of snow-fall left unmelted would lead us to suppose 
that it would have a nearly level surface; and its motion south- 
ward, caused by the pressure of its much greater thickness far 
at the north, shows that these plains sloped toward their boun- 
dary. The Antarctic continent and the interior of Greenland 
are now covered by similar fields of ice. That of Greenland 
rises steeply at its edge, but after a few miles changes to a 
gently inclined plateau, elevated above the highest peaks of 
the land on which it lies, and apparently of immeasurable 
extent. Dr. Hayes found the angle of ascent on this plain to 
‘filled with the material of the drift at least to the height of the 
peaks and ridges which it crossed. Differences of direction 
and angles of descent in the slopes of the surface of ice above, 
; 
