of the United States of North America. 409 



beneath the coal formation, increases gradually in de- 

 scending, until they are but a few degrees from ver- 

 tical, in central Pennsylvania. Mr. "Weaver is satisfied 

 with the existence and identity of this group in York 

 State, but not that it is identical with that which I have 

 traced from the same State and shown to pass imme- 

 diately beneath the bituminous (secondary) coal-field 

 of Pennsylvania in Tioga. 

 3. The Upper Transition and Grawwacke Series, commen- 

 cing at the termination of the red shales and sandstone 

 at the base of the Alleghany mountain, and dipping 

 at a very high angle under that mountain inid the bitu- 

 minous coal on its summit, the whole series being 

 much broken and heaved up on its edges, inclining in 

 several anticlinal and synclinal groups. In Pennsyl- 

 vania this series consists of at least eight zones of 

 (transition) limestone, in general deficient in fossils; 

 and as niany zones of sandstones and conglomerates, 

 stretching parallel with the Alleghany. The aggre- 

 gate of this upper transition system, even on the lowest 

 computation, is of enormous thickness. It comprises 

 four or five troughs or basins containing coal, which 

 on the east side of the State is anthracitous, and on 

 approaching the south-west, contains upwards of six- 

 teen per cent, of bitumen and volatile matter. 

 Mr. Weaver, and one or two other writers, conceive that 

 the whole series, from No. 1 to No. 3, inclusive, is secondary. 

 If so, then must the grauwacke and upper transition series 

 be absent; nor can the red sandstone under the Alleghany 

 mountain and coal-field, be the old red sandstone, as I pre- 

 sumed. 



I must confess that I have not seen beneath the great Alleg- 

 hany coal-field a formation fully answering to the characters 

 of the carboniferous limestone. No such rock interposes be- 

 tween this secondary coal-field and the red sandstone, for the 

 occasional beds of thin gritty gray limestone, resembling the 

 " cornstone " in the old red sandstone, cannot of course be 

 its representative. If we select for this purpose one out of the 

 eight zones of limestone, we might expect to find it in the 

 first and most western; but although this slaty limestone con- 

 tains some fossils in particular localities, it has no claim, par 

 excellence, to the title of the carboniferous limestone. 



In York State the limestone which is thought to resemble 



in geological age and character the carboniferous limestone of 



Europe, appears decidedly loisoer in the series than the group 



I have designated as the old red sandstone, but at the same 



Third Series. Vol. 9. No. 5Q. Dec. 183G. 3 C 



