486 
GEOLOGY OF THE FOURTH DISTRICT. 
Southeast of Rockville, on White creek, we find a greenish shale, with a concretionary 
sandstone, which in some places becomes a conglomerate in the upper part of the layers. 
When not concretionary, it is fit for grindstones. Sandstone appears in nearly all the ravines 
in this neighborhood. 
The bed of the Genesee river, at the Transit bridge, is in a mass of very fossiliferous sand¬ 
stone, some portions of which are slightly conglomerated. 
At Hull’s mills, near Angelica, the rocks are exposed in the bank of the creek, for fifty 
feet or more in height. They consist principally of shale, which contains the fossils common 
to the Chemung group, and among others, the large Pecten-like Avicula. The lower portion 
of the mass is a hard grey sandstone, containing in some parts, great numbers of fossils, among 
which Delthiyris and Strophomena are most abundant. This sandstone has been quarried for 
building ; it is durable, and presents a very good appearance. 
About a mile and a half south of Angelica, sandstone has been quarried, though the greater 
portion of the rock exposed is shale. The sandstone has been used in the construction of a 
mill near the quarry ; though, when first quarried, it is extremely friable, and scarcely coheres* 
Like most sandstones of this region, it contains a large proportion of moisture. 
The sandstone along Van Campen’s creek was quarried by Judge Church, and used in 
building more than thirty years since ; it still remains firm, though somewhat iron-stained 
from the decomposition of pyrites. 
At Philipsburgh, two and a half miles south of Hobbieville, we find a change in the rocks, 
which is indicated by their fossils more than their lithological character. Green shale is the 
predominating portion of the mass ; with some thin strata of sandstone, it occupies the bed 
of the river for an eighth of a mile, and, together with the vertical bank, presents a thickness 
of forty feet or more. Above Philipsburgh, on the Genesee, rocks similar in character occur 
in several places in the bed and bank of the river. At Vandermark’s creek, five miles from 
Philipsburgh, we find the green shale, not so highly fossiliferous, and with it thin courses of 
coarse-grained sandstone, containing abundance of a large species of Delthyris. This fossil 
occurs in a rock of similar texture in many places of the same elevation, and maybe found to 
constitute a definite point, or to mark the termination of some group ; certain it is that along 
this line we find scarcely any fossiliferous rocks above it. 
The next place south of Vandermark’s creek, where rocks are seen, is on Dike creek, near 
Wellsville, at an elevation of sixty or seventy feet above the Genesee, and between fifteen 
hundred and sixteen hundred feet above tide water. The rock at this place consists principally 
of grey sandstone, embracing a brick red or brownish mass six or eight inches thick. This is 
composed of sand, or rounded particles of quartz, with much argillaceous matter, splitting into 
laminae half an inch or an inch in thickness, and is so highly impregnated with iron that it 
stains the hands nearly as much as the oolitic ore of Wayne county, but is not, like that, 
unctuous to the touch. It is considered by the inhabitants as a stratum of iron ore; but its 
specific gravity proves the proportion of metal to be too small ever to repay working. Single 
joints of crinoidea occur in this and the grey rock below. On close inspection, the materials 
