180 
GEOLOGY OF THE THIRD DISTRICT. 
As a group, the sandstone is of a lighter color than the lower one, the greenish or olive color 
being more general, and the shale more disposed to assume the same color when altered. 
Concretions of a large size often appear in the shale and sandstone, the nucleus being more 
solid than the surrounding parts. Carbonate of iron often replaces its fossils, particularly its 
encrinites, which are usually about half an inch in diameter, and different from those of the 
Ithaca or any rock below it. Some of the sandstone masses are loaded with shells, the cement 
being limestone, making a more durable building stone; and some of the varieties make good 
fire-stones, from the mixture of shells; premising^ that a good fire-stone does not mean one 
which will not melt, but which will not crack or fall into pieces when heated in the fires of 
the asheries. 
This group was only distinctly recognized in the counties of Tompkins, Tioga, Cortland, 
Chenango and Broome, and in none of the others. In Tompkins, it covers the towns of Danby 
and Caroline, a small portion of Ithaca, and the southeast part of Dryden ; in Tioga, the whole 
of the county north of the Susquehannah, and a portion on the south border of the river; in 
Cortland, the southwest part of Virgil, and those parts of the towns of Marathon, Willet, 
Freetown and Cincinnatus which border on each other ; in Chenango, the greater part of the 
town of Greene, and some portion further north and to the west of Genegansette river; in 
Broome, all to the north of the Susquehannah, and west of the town of Colesville, including 
the south border of the river, and portions along the river through Windsor and Colesville. 
At the beginning of this group, it was mentioned that an exception existed as to the Che¬ 
mung group being the lowest rock of Broome county. This exception exists at Port Crane 
on the Chenango canal, near the north line of the county. There rocks appear, having similar 
fossils to those of the lower rocks which are quarried around the village of Norwich, and 
those exposed in the sides of the brook to the west of the village of Oneonta. There are 
three fossils at these localities also, which are the same with those of the Hamilton group, the 
Posidonia lirata, Strophomena carinata and Atrypa plebeia; showing that localities existed 
which favored the continuance of certain species, long after their total destruction in others ; a 
subject which requires thorough investigation, and without which the value of fossils as a 
character will not be as deservedly esteemed as they should. It may be well also to mention 
that there are two other fossils very generally distributed throughout the Chemung group, 
which are considered to be the same as the Linear and the Umbonated strophomenas of the Ha¬ 
milton group ; but they have not been sufficiently examined to ascertain with certainty either 
identity or non-identity with them. These shells are small, and therefore more difficult to 
determine, and other objects have appeared to be more important and pressing. 
