164 
GEOLOGY OF THE FOURTH DISTRICT. 
only presenting this appearance, it is probably due in some measure to the cause which ex¬ 
cavated the lake, and which doubtless acted with greater effect upon the softer strata beneath 
the limestone. Upon the eastern shore of Cayuga lake, in the Third District, the influence 
of this agency is more distinctly visible. 
From the quarries on the Seneca outlet, to the west of Waterloo, this rock does not again 
appear for several miles, having evidently been excavated in a direction north of Seneca lake, 
for about the same width as the lake. At Jones’ quarry, where it first appears, in the town 
of Phelps, its eastern edge forms nearly a perpendicular escarpment, showing either a sinking 
down of the rock on the east, or its entire removal. The latter seems more probable, since 
there appears no evidence of causes to produce the former, and there are many reasons and 
facts for inferring that the valley of Seneca lake once extended much farther north than at 
present. 
In Ontario county, at the place just mentioned, the rock is nearly of the same color and 
character as in Seneca county. Farther west it becomes of a lighter grey color, and often 
exhibits a tendency to crystalline structure. At the numerous points along this terrace west¬ 
ward where this rock appears, it presents a rounded outline of a light grey or almost ashen 
color, with projecting nodules or layers of hornstone, which, from weathering, have assumed 
a yellowish color, and are checkered by seams in all directions. Near Oakes’ Corners, the 
course of the railroad has cut through its northeastern extremity ; and along the south side of 
the railroad, for some distance, its northern outcrop is visible. 
At Vienna, the whole rock is well exposed in the bed of the stream, extending from the 
lower to the higher village, and appearing still farther beyond. 
The strata resting upon the Onondaga limestone are principally composed of hornstone ; 
the calcareous matter has been dissolved from the same, and it presents the most rugged and 
irregular appearance conceivable. Where the stream passes over these beds, the calcareous 
portions are worn much deeper, while the hornstone stands up in projecting knobs. The lower 
part of the mass is developed in about twelve distinct strata or beds, of about one foot each, 
some of them varying from twelve to fourteen inches. The central portion of the mass at this 
place has a shaly structure, and is free from hornstone; it contains innumerable small fossils, 
which are scarcely distinguishable by the naked eye. This portion of the rock is blue, but 
weathers to an ashen color. 
The shaly division is again succeeded by compact limestone with hornstone, and terminates 
upward in shaly calcareous, thinly laminated strata. Few fossils are found where the horn¬ 
stone is abundant, but in other parts of the rock they are common. 
Two miles west of Vienna, some strata of this rock, containing very little hornstone, are 
exposed over considerable surface. The rock is compact, of a light greyish blue color ; it is 
readily quarried, and furnishes good building stone. The character exhibited in the bed and 
banks of Flint creek at Vienna, is the prevailing one along the outcrop of this rock westward. 
In the bed and banks of Mud creek, above the village of Freedon, it presents nearly the 
same character, except that there is far less hornstone. The central portion is shaly, con- 
