154 
GEOLOGY OF THE FOURTH DISTRICT. 
twenty feet or more of chert in thin irregular layers, with scarcely any calcareous matter. 
This cherty mass contains the usual fossils of the Onondaga limestone, and they are persistent 
as far as the hornstone continues. The cherty layers are again succeeded by thin-bedded 
compact, bluish or greyish blue limestone, marked by fossils typical of the next higher rock. 
This example furnishes an instance where the fossils of the lower limestone pass into the 
hornstone, which eminently characterizes the next rock, and from which its name is taken. 
Should such cases prove to be of frequent occurrence, it might become a source of difficulty 
in identifying these rocks. The fact is stated as occurring, not for the purpose of throwing 
difficulty or obscurity in the way of the observer, but to prepare him for some variations in 
character, which will ever be found in all subdivisions which can be made; and if he be not 
previously made acquainted with them, he is likely to experience more difficulty in endeavor¬ 
ing to force rocks to accord with arbitrary descriptions, than from a knowledge of any such 
variations from the general rule. 
About two miles northeast of the point just described, the cherty mass has greatly dimi¬ 
nished, and the Onondaga limestone in its typical characters is presented in several thick- 
bedded regular strata. It is of a light grey, often approaching white, composed of comminuted 
fossils, and marked by the presence of large numbers of crinoidal columns, Cyathophylli and 
Favosites. The crinoidal portions are often reddish or pink, and give a beautiful variegated 
appearance to the rock. The quarries at this place belong to Messrs. Clifford and Rich. 
Half a mile farther west, there is another similar quarry. The rock is extensively wrought, 
sawed into slabs, and polished for hearthstones, mantels and other purposes. It is also much 
used for buildings. From these quarries the stone for the Court House at Batavia was ob¬ 
tained. There is scarcely a better locality in the district for an exhibition of the typical 
features of the rock. 
Following the outline of the terrace westward, this rock appears in several points, though 
but obscurely developed, sometimes being represented by a single stratum of less than two 
feet in thickness. In the town of Newstead, Erie county, its place is marked by a thin band, 
almost entirely composed of Favosites and other corals, with a few calcareous laminae, and 
a large proportion of shaly matter. The latter is partially decomposed, and the coralline 
masses appear as if imbedded in a ferruginous mud. 
At Clarence Hollow this limestone is but meagrely developed, a thin stratum resting on 
the terminating rock of the salt group, being all that is seen. A mile west of this point, how¬ 
ever, it is well developed, appearing as a grey sub-crystalline rock, very coarse grained, and 
crumbling under a blow of the hammer. At this place it abounds in its typical fossils, and 
in some places the mass is nearly composed of crinoidal columns and Cyathophylli. From 
this place to some distance west of Williamsville, it continues to be a well-marked and highly 
important rock. In some points it contains large numbers of silicified corals, and some irre¬ 
gular nodules of hornstone, which render it unfit for lime burning. Every point, however, 
where free from these substances, and the grey crinoidal mass well developed, is marked by 
one or more limekilns, and it will be found a convenient guide to this rock throughout Erie 
county to inquire for these. 
