1877.^ Oil [Ashburner. 



"par excellence," having a thickness of 3000 feet at Mauch Chunk on the 

 Lehigh river. 



2d. There is no marked distinction in physical aspect or composition 

 between the lower and upper members of No. XI eilier in Western Penn- 

 sylvania, where the limestone is found, or in Eastern Pennsylvania, where 

 it is entirely wanting. 



3d. The topography produced by the upper member of No. X is so 

 different from that produced by the red shale XI below the limestone as 

 to suggest a classical distinction between the two. 



The lower member is made up principally of red sandstones and shales ; 

 with alternations of coarse-grained, gray and greenish-gray, flaggy sand- 

 stones and shales ; the latter predominating toward the bottom. 



The lower member is devoid of all remains of fossil life, as is also the 

 upper member. 



In the layers transitional between the Umbral (XI) and Vespertine (X) 

 occurs an iron ore bed of some local importance in Trough Creek basin. 

 Its precise stratigraphical position was not determined ; but it is 

 probably not far above what we have considered as being the top of No. X . 



This ore of XI has been developed to some extent at the old workings 

 of the Trough Creek furnace, at the eastern base of Terrace Mountain. 

 "Here the bed occurred in balls closely imbedded in a little earth and 

 was of a number of varieties." (Rogers, Vol. I, page 539.) "Several of 

 these varieties were of a common compact brown ore, seldom exhibiting 

 any hematitic structure, but having a smooth jaspery surface and brittle 

 fracture." 



"The Hopewell ore-openings display the ore bed on both sides of the 

 gap cut through Terrace Mountain by Yellow creek. A tunnel 90 feet 

 long reached the ore on the south side of the gap 90 feet below its outcrop, 

 the ore being from 20 inches to 3 feet thick, interposed between the sand- 

 stone below and the red shale above, and interstratified with more or less 

 clay. The adjoining red shale lies in thick but very soft strata, is friable 

 and of an intense red color directly below the ore. Thin layers of a more 

 sandy ore are interleaved with the red shale." 



The three horizons of economical importance are therefore : 



1, that of the Ore bed directly under conglomerate No. XII ; 



2, that of the Mountain limestone ; 



3, that of the Ore bed directly above No. X. 



No. X. 



Pocono ( Vespertine) Sandstone. 



Upper member (massive and flaggy sandstone), 



Nos. 313, 211 and 310 610 feet. 



Middle member, 1 . Coal bearing strata Nos. 809 



to 158 inclusive, (New River series) 313 



2. Conglomeritic strata, characterized bj' 



false bedding, Nos. 157 to 137 inclusive 380 J 

 Lower member (sandstone and shale), (Nos. 126 to 117) 830 



PROC. AMER. PHILOS. SOC. XVI. 99. 3p 



693 " I 2133' 



