194 BRIGHAM—TOPOGRAPHY AND DEPOSITS OF MOHAWK VALLEY. 
and from three-eighths to half an inch thick has been plucked, leaving 
a ragged rim to the east, north, and south, while the westward edge of 
Ficure 1.—Striated Surface of Limestone at Amsterdam. 
The diagram is about one-half natural size. The arrow indicates the westward direction of strie. 
g 
the depression is, with one slight exception, well subdued. The inclosed 
space is as perfectly polished as the surrounding area, and on the west 
the general surface drops by a narrow bevel to a shghtly lower plane. 
Drirr Drposits 
PREVIOUS INVESTIGATIONS 
Considering that the Mohawk valley has long been known to geologists 
as an important channel, published observations concerning it are sur- 
prisingly few. Vanuxem alludes to a “ determinate order of alluvial de- 
posits,” namely, blue clay, covered with sand and sometimes with rolled 
stones. He mentions a few of the large bodies of drift.* Dana, in his 
paper on the Mohawk Valley glacier, thus refers to the character and 
importance of the terraces : 
“<The subject of river terraces, or stratified post-Tertiary deposits, on the Mohawk 
and its tributaries is also one of great interest in this connection and merits a thor- 
ough examination. The deposits have some relation to the drift, as they belong 
to the epoch immediately following—the Champlain epoch—and consist in part, 
at least, of material that had been transported by the ice. They are of unusual 
extent on the East and West Canada creeks and other northern tributaries of the 
Mohawk.”’ 
Chamberlin, as already noted, gives a general description of the drift 
shoulders between Utica and Little Falls, and Merrill alludes to them in 
*L, Vanuxem; Geology of the Third District, p. 212. 
