QUATERNARY DEPOSITS. 
219 
Pratt’s-Hollow. In Onondaga valley there are two deposits, one on the Indian reservation near 
the mouth of South-Onondaga valley; there the hills are highest, and the accumulation the 
greatest, some of the hill appearing to be over one hundred feet in height: the other is a lesser 
deposit, and near the head of the valley. A similar but smaller deposit exists at the head of 
Otisco valley, near where the road takes a rise into the valley which leads to Homer; also 
another in the head of the valley which extends south from Skaneateles lake, in the town of 
Scott. The last great deposit is in Cayuta creek at the head of Cayuga lake, and extends 
for miles along the creek. 
Some of these deposits greatly resemble the hills of loose materials which rise in the valley 
near Fall and Cascadilla creeks, near Ithaca. The hills appear to have been formed by the 
waters of the creeks when the lake was at a higher level; for where such substances are de¬ 
posited in deep and tranquil waters, there is no tendency to diffusion; the head of the lake 
upon which Ithaca is seated, being a perfect flat. 
There are numerous points where the alluvial appears to have been formed over the hill 
side, besides those near the mouths of the creeks near Ithaca; such is the mass on the west 
of Onondaga village ; the descent into the valley northwest of Waterville ; north of the village 
of Greene in the Chenango valley, etc. etc. 
These deposits of alluvion near the line of dividing waters, greatly resemble certain accu¬ 
mulations of similar deposits noticed in the survey of Massachusetts, called diluvial elevations. 
The whole of the district south of the north line of the Helderberg range, shows an im¬ 
mense accumulation of alluvial deposits, either filling up the valleys and forming level surfaces, 
or ranging by the sides of the valleys as terraces, or thrown into irregular hills in the valleys, 
and also occurring on the heights apparently in no regular order. The deposits consist of 
rolled stones large and small, sand, clay and earth. The rolled stones are in prodigious amount, 
nearly two-thirds of which are from rocks north of the Helderberg range. They consist 
chiefly of primary rock, and grey and red sandstone. In some localities, those of limestone 
are numerous ; and where they exist, as their gravel and soil are often present, they give rise 
to deposits of tufa or lake marl; the former kind if air only be present, the latter if deposited 
in water. 
The excavation of the Chenango canal from Oriskany falls south is entirely in alluvial ma¬ 
terials ; showing frequently, in the northern part of the town of Madison, a mass of gravel 
and large rolled stones as an upper deposit. Below the rolled stone, there is often a deposit 
of blackish or dark-colored sand, fine or coarse, which is the common sand of the whole of 
the south valleys. The lighter colored sands exist, but are rare comparatively. The lower 
part of the canal at Chenango forks was in a sand of the kind; above which was a mass of 
coarse gravel from six to eight feet thick, with rolled stones from one to eight inches in diame¬ 
ter, having on the top finer gravel with thin layers of sand. 
The clays in that part of the district are usually of a lighter color than those of the Mohawk : 
the dark ones exist, but are rare. Small pebbles of limestone appear to exist also in the 
clay, as at South-Norwich ; some of the bricks are apt to burst and crumble after being burnt 
and exposed to the weather, showing the northern origin of at least a portion of its materials. 
