Chemung and Catshill.— Stevenson. 11 
is shown along the Baltimore and Ohio railroad as it follows 
the Potomac river. Of course there are variations in struct- 
ure; Mr. N. H. Darton tells me that the conglomerates are 
wanting in the section near Staunton, Virginia, but this is merely 
local as they are present elsewhere. Further north, the upper 
beds, or Catskill, have an increased proportion of shale, often 
blood-red, and the sandstones show a more marked conchoidal 
fracture, while the whole section has a greatly increased thickness. 
The Pennsylvania line is reached but a few miles north from 
the Potomac along the outcrop. Crossing that line, one enters 
Fulton county, where the succession is:* 
1. CatskrLu. Shales 1,600' 
Sandstone and shale 2,100’ 3,700! 
2. CuEMUNG. Shales 1,000' 
Upper conglomerate 10’ 
Shales and sandstone 950/ 
Lower conglomerate 10’ 
Shales and flags 1,850’ 3,820’ 
The close resemblance to the Virginia section is apparent at 
once, the most notable change being simply the great increase in 
thickness of the upper portion. The upper Catskill consists for 
the most part of soft deep red shales with occasional sandstones ; 
but the lower Catskill is made up of brownish or greenish to red, 
eross bedded, almost laminated sandstone, often looking as 
though it were worm eaten. Sometimes a large fragment re- 
mains on a hill top, resembling much a pile of thin boards. 
Occasionally more massive sandstone prevails, as along the 
Juniata river in central Bedford county of Pennsylvania, where 
no tendency to lamination was seen. The Catskill appears to be 
wholly non-fossiliferous along the eastern outcrop from central 
Virginia into New York. 
The absolute limit between Catskill and Chemung is indetermi- 
nable, for the passage from one to the other is practically imper- 
ceptible at most localities; the line drawn at any locality, whether 
on stratigraphical or on paleontological grounds, is almost certain 
to be unsatisfactory at any other. In Fulton county, however, 
a marked lithological change occurs at about 1,000 feet above 
the Upper Chemung conglomerate, for there the alternations of red 
*Geology of Bedford and Fulton counties, J. J. Stevenson, Harrisburg, 
1882, pp. 73,75, 82. I have re-arranged the section somewhat, placing 
the line between Chemung and Catskill 200 feet higher than in the 
original. 
