280 
GEOLOGY OF THE FOURTH DISTRICT. 
129, 
1. Chemung group. 2. Grey sandstone, with beds of oolitic limestone. 3. Grey limestone, oolitic above. 4. Diagonally 
laminated sandstone and conglomerate. 5. Coal measures. 
In the Fourth District, the thinning margin of the Old Red Sandstone, from the large pro¬ 
portion of ferruginous matter it contains, has usually more the appearance of an iron ore than 
a sandstone. It appears to be a compound of sand, clay, and calcareous matter, with a large 
proportion of the hydrate of iron, and contains, in abundance, small fragments of bones and 
scales of fishes. These are generally too small and too much worn to be recognized, except 
in the general similarity with better characterized specimens of scales and bones of Holop- 
tychus from other localities. In some places the whole mass is an iron ore of tolerable 
quality, containing probably 20 or 30 per cent, of that metal. In such cases, however, it is 
very thin, and I have been unable to find any rock above it in connection. 
This rock is much better developed in the First and Third Districts ; and it is to be hoped 
that some one with powers of investigation and description, like Mr. Miller of Glasgow, will 
one day give us a work upon the Old Red sandstone of the Catskill mountains, similar to his 
on the same rock in Scotland.* 
Localities. — The principal localities where this rock can be seen in the district, are near 
Wellsville on the Genesee; and at another point near Spring mills, in the southeastern part 
of Allegany county. It likewise appears in several places in Steuben county, on the tops of 
the hills between the Canisteo and the south line of the county. 
The mass is too limited in extent to produce any important influences upon the surface or 
soil, though it tinges the latter of a deep red, like the red shale of the Onondaga salt group. 
Organic Remains of the Old Red Sandstone. 
In passing from the rocks of the Chemung group to the Old Red sandstone, we find a marked 
change in the organic contents. Immediately below the latter we have green shales and shaly 
sandstones charged with shells of Delthyris, Strophomena and Atrypa ; while after leaving this 
♦Few works have ever appeared on the subject of geology, of greater interest than the book entitled “The Old Red 
Sandstone, or New Walks in an Old Field,” by Hugh Miller. The clear and fascinating style of the author has here rendered 
highly interesting, what in most other hands would have consisted so much of dry detail as to have been forbidding to many 
readers. This work, and other writings of the same author, show what can be accomplished by a man who began life as a 
quarryman, and who, having toiled through all the privations and discouragements of that kind of life, now stands among 
geologists in such a position that the Rev. Dr. Buckland offers to give his right hand to possess the same felicity of descrip¬ 
tion as Mr. Miller. 
