170 HELDERBERG DIVISION. 



outcropping edge all the way from mar Catskill to Cayuga bridge. It is eighteen inches 

 thick al Auburn. It extends on this line no farther west than the last mentioned locality. 

 It is proper i" Bay, in tliis connection, that from its hardness, it frequently forms a narrow 

 terrace, something more than merely an outcropping edge ; but it never properly consti- 

 tutes the surface rock of a continuous helt of country, as many of the New-York rocks do. 



In giving the preceding localities, it is not designed to intimate that they are the only 

 ones al which this nuk may lie examined with profit, but they are leading localities in the 

 range in which it appears in its northern outcrop. Many others exist at intermediate places, 

 and this is perhaps found with a greater certainty than any other in the New-York series, 

 and heme becomes one of the important landmarks in studying the system. 



Thickness of the Oriskany sandstone. At Leeds, compressed between its associates, it is 

 only six inches thick ; at the rise of the Helderberg mountain, east of Clark's, it is one 

 foot; ai Schoharie, two feet; at Cherryvalley, about eighteen inches; at Oriskany falls, 

 twenty feel ; at Perryville, and below Cazenovia, only a few inches ; between Elbridge 

 and Skaiuaieles, on the old Seneca road, thirty feel ;* at Auburn, eighteen inches ; a 

 mile and a half south of Onondaga hollow, seven feet.* In places still farther west than 

 any which have been named, a sprinkling of its peculiar angulai sand is all which indi- 

 cates its continuance ; yet out of the State of New- York, and within the limits of Penn- 

 sylvania, this rock is said to be seven hundred feet thick. 



Relations of t his rock in the J\'cw-York scries. In Hudson river district, its relations have 

 been spoken of: it succeeds, in the ascending order, the Encrinal limestone ; above, it is 

 succeeded by the Cauda-galli grit. West of Cherryvalley, however, where some of the 

 succeeding rocks disappear or thin out, it is immediately below the Onondaga limestone. 

 These are the relations of the rock in Onondaga and Cayuga counties. The Hydraulic 

 limestones are in contact with it below, and the Onondaga above. We have already 

 stated that the Pentamerus, Delthyris and Encrinal limestones disappear in succession. 

 The same fact exists in regard to the two rocks which intervene between the Oriskany 

 sandstone and the Onondaga limestone. Near Mr. Geddes, at Tyler Post-office, the 

 Oriskany is represented by a few boulders of the Niagara limestone. One was removed 

 from beneath the Onondaga limestone, and found to be more than a foot in diameter : 

 this mass belonged to the bituminous part of the Niagara limestone. 



Some peculiarities worthy of notice which accompany this rock. At a few localities, the 

 lower part of the rock is a dark-colored sandy limestone. Fossilized wood, in angular 

 pieces, as if broken by violence, have been found in the rock at New-Scotland. 



This rock is widely distributed in the drift south and southeast of the Helderberg. At 

 the base of the Catskill mountains, in many of their gorges, and on the summits of the 

 highest ridges in Greene and Albany counties, excepting those of the Catskill, boulders of 

 the Oriskany sandstone are abundant. Many have found their way over the valley of the 

 Hudson, and lie upon its eastern side, far beyond the limits of the rock. 



* Vanuxem's Report, p. 126. 



