650 



HISTORICAL GEOLOGY. 



section from the heart of the Anthracite region, between Nesquehoning 

 Valley on the west (left in section), and Mauch Chunk. It is from the 

 Eeport of C. A. Ashburner, of the Geological Survey of Pennsylvania. The 

 length is about 1200 yards (the scale of the figure being lOUO feet to the 

 inch). The flexures to the west have their summits pushed westward 40° 

 beyond the vertical. The folded rocks consist of beds of Anthracite, and 

 intervening strata of shale and sandstone ; and the Anthracite beds include 

 the great "Mammoth bed" (lettered at its outcrop E, E,^ E-), which is 13 

 to 27 feet thick, and the bed F (outcropping at F,^ F,^ F,^ F,^ F^), 11 to 20 

 feet thick, besides one of eight to nine feet. The " Mammoth bed "is 

 doubled on itself at E\ Fig. 1026, from Lesley, is from the Anthracite 



1026. 



Section on the Schuylkill, Pa.; P, Pottsville, on the Coal-measures (14). Lesley. 



region of Pottsville, about 30 miles south of west of Mauch Chunk. All the 

 Paleozoic formations from the bottom of the Paleozoic (2) to the last, the 

 Carboniferous (14), are here flexed together: No. 2 being Cambrian; 3, 

 Canadian ; 4, Trenton ; 5, Niagara ; 7, Lower Helderberg ; 8, Oriskany ; 

 9, Corniferous ; 10, Hamilton; 11, 12, Upper Devonian; 13, Subcarbonifer- 

 ous ; 14, Carboniferous. Fig. 1027, from H. D. Rogers, in which the flexures 



1027- 



Section of the Coal-measures, half a mile west of Trevorton Gap, Pa. H. D. Rogers. 



are more gentle, is from Trevorton Gap, 45 miles west of Mauch Chunk. 

 The whole Anthracite region has been thus upturned. 



Constitution of the Coal-measures. — Beds of sandstone, shale, clay, and 

 limestone, with occasional beds of coal, and a bed of fire clay commonly beneath 

 the coal-bed, make up the Coal-measures. About one foot in 40 of the total 

 thickness is usually good coal ; but in the Upper and Lower Productive 

 Measures, the proportion is larger, rising to one foot in 20. 



The following tables, 1 A, 1 B, 2, 3, 4, derived from the reports of the 

 recent Pennsylvania Survey (1, 2, and 3, by J. J. Stevenson, and 4, by H. M. 

 Chance) will give a general idea of the many coal-beds in the series in 

 western Pennsylvania, from the Upper Barren series to the Lower Productive 

 Measures, and of their alternating beds of sandstone, shale, limestone, fire 

 clay, and iron ore : 



