322 
GEOLOGY OF THE FOURTH DISTRICT. 
No theory of this kind, moreover, seems sufficient to account for the grooved and striated 
surfaces of the rocks in place, which hold a uniform direction, and which occur in all situa¬ 
tions, and upon the highest and lowest points. In all situations which have been observed 
beyond the influence of deep valleys, these scorings or striae have a uniform direction, or 
varying but a few degrees from N.N.E. and S.S.W. 
The local origin of nearly all, and perhaps all the ancient drift of the district under con¬ 
sideration, can be shown by an examination of numerous sections upon the lake shore, in the 
river courses, and in artificial excavations which reach to the rocky strata. These sections, 
where made in situations beyond the reach of modern disturbing causes, show very clearly 
the conditions under which the superficial detritus has accumulated. The action of the pre¬ 
sent ocean upon cliffs and beds of rock extending beneath its surface, is nowhere more clearly 
represented than in the sections of detritus resting upon the stratified rocks of western New- 
York. 
The shores of Lake Ontario offer some of the most instructive exhibitions of this kind, and 
indeed it might almost be considered a continuous section from one extremity of the district 
to the other. The following section on the east side of Irondequoit bay, illustrates in a perfect 
manner the general character of these superficial deposits. 
158. 
7. The soil of sandy loam. 
6. A coarse deposit of pebbles of the Medina sandstone below, with gravel and sand. 
5. Stratum of pebbles and sand. 
4. Stratum of sandstone pebbles, cemented into a conglomerate by oxide of iron and carbonate of lime. 
3. Bed of fine sand. 
2. Fragments and rolled masses of the sandstone below, with gravel and sand. This contains a few pebbles of the 
shaly, calcareous sandstone next on the north. 
1. Medina sandstone. Shaly, with bands of green. 
Numerous similar sections, varying in some unimportant details, might be given, all showing 
that the older deposit resting upon the red sandstone is composed of fragments of that rock, 
more or less worn, with a small admixture of other materials. This red gravel of the lower 
deposit is always to be relied on, as indicating the immediate proximity of the sandstone. The 
