124 
GEOLOGY OF THE FOURTH DISTRICT. 
of the group, but it is not marked by the striated or columnar appearances usually seen, and 
the irregular cavities which are sometimes lined with crystalline substances. 
South and southwest of Newark, in Wayne county, the limestone separating the two ranges 
of plaster beds is seen on the surface in several places, presenting an appearance as if cut or 
hacked. These markings extend but a few inches continuously, and have two directions, 
frequently crossing each other, and evidently partake of the nature of joints, the rock breaking 
in these directions much more easily than elsewhere. This character is prevalent in that 
portion of the group throughout the district. 
At the locality just named gypsum, in small rounded masses, is found at some depth below 
the surface, but it is nowhere quarried in this neighborhood. The surface presents, in a small 
degree, what is more fully developed in Monroe county, being covered with small mounds or 
dome-shaped elevations, caused by the sinking down of the strata between the beds of gyp¬ 
sum. 
The rock surrounding the higher range of beds is usually more argillaceous than in the lower, 
the latter being frequently a compact, slaty limestone, enclosing a small quantity of soft marl 
immediately surrounding the mass of gypsum. It is probably owing to this character of the 
rock that the lower gypsum beds are purer and more free from admixture of argillaceous 
matter than those above. 
In the Annual Report of 1839, it was stated that the gypsum (principally crystalline) near 
Newark, the beds near Port-Gibson, and south of that point, and those on the Canandaigua 
outlet belonged to three distinct ranges. There still seems good reason for treating them in 
the same manner, the two upper ones belonging to the two regular ranges of beds, and that 
near Newark being perhaps only a greater development of the second division of the group 
which usually presents only thin seams or small nodules of this mineral. 
Westward, along the Canandaigua outlet, there is little gypsum seen after leaving the town 
of Phelps ; though the rocks of the higher part of the group are still visible, even as far as 
the point where the course of the outlet bends southward. West of this point, as far as 
Mud creek, the great accumulation of drift does not admit any exposure of these deposits. 
That they exist along this distance there can be no reasonable doubt; and more especially 
since a bed of gypsum has been discovered near the village of Victor. This fact also leads 
to another observation, which should be borne in mind as applicable to a large portion of the 
country occupied by this formation east of the Genesee, and within the limits of the Fourth 
District. Many of the hills apparently of drift or alluvial, and rising from fifty to one hun¬ 
dred feet above the surrounding country, are in reality composed of outliers of these marly 
deposits, with only a thin covering of the loose materials. 
The same remarks made in reference to the western part of Ontario county, apply equally 
to that portion of Monroe county on the east side of the Genesee. Although the gypsum beds 
have not been found, there is every reason to believe that they exist beneath the superficial 
accumulations. 
On the west side of the Genesee river, the third division of this group, embracing the 
