CORTLAND COUNTY. 
289 
building material, shows itself on the lake shore to the south of Aurora. These two kinds 
as to hardness, form the great mass of the group. Fossils are in great profusion in this 
county, some detail of which was given under the head of the group. In the ravines near 
Kidder’s ferry, the encrinal limestone, which forms a part of the group on Cayuga lake, there 
appears forming the first falls. 
Tull]) limestone. This rock appears near Yannetten’s mill in Sempronius ; at the falls at 
Montville, and those of Moravia; on the opposite side of the valley, on the road to Stuart’s 
corners ; on the road from Aurora to Ludlowville, in two places ; and in the ravines whose 
waters flow into the lake from the north line of Genoa to Tompkins county. It is usually 
about sixteen feet thick, some of its separate layers being several feet in thickness. They 
differ greatly in purity: some make a strong, but not a white lime. From its hardness, it 
generally forms the falls of the brooks and other water courses, where more usually it is seen. 
The Genesee slate. This is well seen in the ravines near Kidder’s ferry, resting upon the 
Tully limestone, with a thickness of over eighty feet; showing a range of septaria near the 
Tully limestone, and another near the top of the mass. The thickness in this ravine appeared 
to be greater than farther south. The slate shows itself in other localities, but not to the same 
advantage. 
The Portage and the Ithaca groups. These terminate the whole of the rock series of the 
county, being the upper ones resting upon the last named one. It consists chiefly of shale 
and thin layers of sandstone, forming the base of the group. It covers all those portions to 
the south of the county, excluded from the limits of the Hamilton group. 
Since the close of the survey, an interesting note was received from David Thomas of 
Scipio, accompanied by some small cockscomb crystals of gypsum from the upper part of 
the Quaternary or Chittenango deposit near Springport, which is made up in great part of the 
gypseous red shale. The crystals had not been observed. There was also a part of a jaw of 
a small ruminant animal, supposed to have been derived from the same deposit, and appear¬ 
ing from its color, etc. to be in a fossil state. The writer of the note also directs attention to 
the different colored bricks, which the clay at Carr’s brick-yard above Springport produces ; 
part of the mass burning red, and a part of a sulphur color, showing a twofold origin or 
source from whence the clay was derived. The crystals of gypsum, and the jaw, are in the 
State Collection. 
10. Cortland County. 
The same characteristic features of the south part of Onondaga county, namely, broad and 
flat valleys, and low hills, extend into Cortland county, through the towns of Preble, Homer, 
Truxton, and to the south of that town towards Solon. The hills rise to the south ; the 
whole drainage of the county, with the exception of a small part in Virgil, being effected by 
the Tioghnioga or Onondaga river commonly so called. This river presents no such barrier ; 
their are no falls, but rapids ; the valley south, with some few exceptions, is narrower and less 
Geol. 3d Dist. 37 
