CHAMPLAIN DIVISION. 
377 
the course of the Hudson, from Baker’s falls on the north, to the Highlands below Newburgh 
on the south. The borders of the lake are composed principally of argillaceous slate, which 
extends back to the more elevated ridges, where in many places it is overlaid by greywacke 
or greywacke slate, and in some places evidently alternates with it. 
“ On the eastern shore of the lake, three miles from its southern termination, there is a 
singular and interesting stratification of these rocks, at a place called Snake hill. This hill 
projects into the lake for some distance, and rises abruptly more than two hundred feel above 
the level of the water, presenting a naked and almost perpendicular front, which looks to the 
west and southwest, where the different strata are as regular and well defined as xhough they 
were painted on a wall. They rise from the water in regular succession along the southern 
part of this front, and pursue an elevation of from thirteen to fifteen degrees to the northwest, in 
straight and parallel lines, until they arrive towards the northern termination of this promontory. 
Here they make an abrupt curve, and pass up the mountain in an oblique direction to its sum¬ 
mit, producing a declination exactly in an opposite direction. The curve made by the strata 
taking an opposite course, is the segment of a circle, the diameter of which would not exceed 
twenty or thirty inches. The strata are of different dimensions, varying from half an inch to 
two feet in thickness, and consist of alternate layers of argillaceous slate and greywacke or 
greywacke slate. The greywacke contains impressions of shells in great abundance ; they 
consist principally of bivalves, and both the formations effervesce with acids. 
“ The Plate 36, fig. 6, is a full view of the hill with its curved strata, as they appear from 
the water; the back ground is the elevated ridge which separates the lake from the Hudson 
on the east. 
“ Plate 36, fig. 7, is a section of the hill, showing more distinctly the arrangement, eleva¬ 
tion and curve of the different strata. The dark lines may be supposed to represent the ar¬ 
gillite, and those of a lighter'shade the greywacke. 
“ It is impossible«to examine this locality, without being strongly impressed with the belief, 
that the position which the strata here assume could not have been effected in any other w'ay 
than by a power operating from beneath upwards, and at the same time possessing a progres¬ 
sive force ; something analogous to what takes place in the breaking up of the ice of large 
rivers. The continued swelling of the stream first overcomes the resistance of its frozen sur¬ 
face, and having elevated it to a certain extent, it is forced into a vertical position, or thrown 
over upon the unbroken stratum behind, by the progressive power of the current.”* 
The horizontal and slightly inclined strata of slates and grits of the Hudson river group, 
lying on the west of the anticlinal axis, as traced from New-Jersey to Saratoga lake, were 
formerly considered as more recent strata than the upturned rocks of the Hudson valley, and 
as resting unconformahly on them. It was not until the labors of the geological survey were 
more than half completed, that sufficient evidence was obtained to establish the fact with cer- 
Geol. 1st Dist. 
American Journal of Science, Vol. ix, pp. 1, 4. 
48 
