458 
GEOLOGY OF THE FOURTH DISTRICT. 
when combined with the muck with which it is deeply covered. There are several small de¬ 
posits of marl near the northern edge of the county, upon the Onondaga salt group. There 
is a large muck swamp near Victor, which is probably underlaid by marl. This substance 
will, without doubt, also be found in the swamps at the head of Hemlock and Canadice lakes. 
YATES COUNTY. 
The rocks occupying the greater part of Yates county are similar to those of the southern 
part of Ontario, only the most elevated parts of Barrington and Starkey being occupied by the 
rocks of the Chemung group. The outlet of Crooked lake has excavated its channel through 
the rocks of the Portage group, Genesee slate, Tully limestone, and the upper part of the 
Hamilton group, presenting all these in their order along its course. 
Northwestedly from Penn-Yan, and at Shepherd’s quarry, the rocks of the Portage group 
are well developed. At this place the lower part consists of alternating arenaceous and argil¬ 
laceous strata, containing much iron pyrites, large fragments of carbonized vegetables, and 
occasionally large Orthoceras. 
The lower part of the group furnishes large and fine flag-stones, which are used in the streets 
of Penn-Yan. These thin layers often contain small irregular concretions, surrounded by a 
coating of shale which soon disintegrates, and the concretions become loosened, in many in¬ 
stances injuring the stone. Some of these strata are shaly, and soon wear away on exposure. 
This group appears about a mile south of Penn-Yan, in Sartwell’s ravine, where its con¬ 
nection with the black shale below is very evident; the characteristic Lingula of the latter 
is found in abundance. 
The same group extends west through the towns of Jerusalem and Italy, and appears in 
many of the streams and ravines near the west branch of Crooked lake. The thin layers of 
sandstone are used throughout the country for step-stones, foot-walks, and in many instances 
for enclosures, though rarely for building stones. 
The outlet of Crooked lake affords a good opportunity of examining the higher part of the 
Hamilton group, and its connexion with the Tully limestone and the higher rocks. 
The lower part of the Portage group is developed near Penn-Yan, and on the west bank of 
Crooked lake ; it presents a more arenaceous character than on the Genesee river, and contains 
some fossils not seen elsewhere. 
From the nature of the strata, there are few economical mineral products in this county. The 
outcropping of the Tully limestone along the Crooked lake outlet, is of great importance in 
furnishing lime. Farther south, near Big-stream point, where this rock is concretionary in 
structure, it affords a good hydraulic cement, which promises to be of importance to this 
part of the county. 
