124 THE CAMBRIAN. bull. 81. 



PENNSYLVANIA. 



In the second annual report of the State geologist of Pennsylvania, 

 Prof. H. D. Rogers summarizes in a table the order of stratification, 

 the geographical position, composition, and thickness of the lower 

 Secondary formation in Pennsylvania, east of the Susquehanna River. 1 

 The description of formation No. I, or the sandstone of the South Moun- 

 tain, is as follows: 



In the ascending order, the first formation which we meet with, reposing on the 

 primary rocks of the South Mountain, * * * is a remarkably compact and rather 

 fine-grained sandstone, usually white or of some light shade of gray. * # "* The 

 formation ranges, according to my present belief, from the Delaware, at Eastou, more 

 or less iuterruptedly across the State to the Maryland line, pursuing an undulating, 

 irregular belt, coinciding with the northern and northwestern side of the chain of 

 hills most commonly called in this State the South Mountain, the prolongation of the 

 Highlands of New York and of the Blue Ridge of Maryland and Virginia. 2 



It contains, as far as yet examined in Pennsylvania, very few organic remains, the 

 best defined species discovered in it being a marine plant, indicative of the oceanic 

 position iuto which the materials of this stratum were originally swept. 



I have satisfied myself that this rock is not confined to the Appalachian region of 

 Pennsylvania, but that it possesses a prodigiously extensive range, not only through 

 Maryland and Virginia, but in a contrary direction through New Jersey and New 

 York, and I believe beyond those limits, constituting everywhere the lowermost for- 

 mation of the widespread Secondary strata which it encircles in a somewhat inter- 

 rupted belt, following the primary boundary of these rocks from Tennessee to Lake 

 Champlain, and thence northwestward to the northern shores of Lake Huron and 

 Lake Superior 3 



Prof. Rogers recognized the sandstone at many points iu New Jersey 

 and New York, and considered it identical with the formation in north- 

 eastern New York, described by Prof. Eaton under the name of Cal- 

 ciferous sandrock, 4 and states that it is probably the same stratum 

 which Dr. Bigsby has mentioned as existing on the north side of Lake 

 Huron. 5 In the table showing the order of stratification, formation No. 

 I is assigned a probable thickness of 1,000 feet. 



A description is given in the third report 6 of the geographic distri- 

 bution of the sandstone as it occurs in the various counties of the south- 

 eastern portion of the State. 



In Northampton and the eastern corner of Lehigh the sandstone * * * is sub- 

 ordinate in importance to the gueiss and other primary rocks on which it rests. 7 



. ^ ___ 



1 Second A.nnual Report on the Geological Exploration of the State of Pennsylvania. Harrisburg, 

 1838, oppo. p. 19. 



2 Op. cit.,p.21. 



3 0p.cit.,pp.22,23. 



4 The Potsdam sandstone was not differentiated from the calciferous sandrock hy Eaton, He in- 

 cluded the sandstone and the superjacent calcareous sandstone, under the common name of calciferous 

 sandrock, as one formation. 



6 Op. cit., p. 23. 



6 Rogers, Henry D. Third Annual Report of the Geological Survey of the State of Pennsylvania. 

 Harrisburg, 1839, pp. 14-1G. 



7 Op. cit., p. 15. 



