180 



TRANSACTIONS OF THE 



prolonged to an unknown distance, or from contraction 

 and consequent subsidence on either side — that, with the 

 exception of some cases of unconformableness in the con- 

 torted limestones and undulating soft shales, I have ob- 

 served its influence has been exerted over a breadth of 

 thirty miles on one side of the anticlinal line, and from 

 twenty-five to thirty miles on the other. I have reason 

 to conceive, further, that on the west side tliis anticlinal 

 line the strata uniformly dip to the west under the se- 

 condary formations, and on the east towards the pri- 

 mitive region ; that this line ranges parallel with and is 

 co-extensive with the entire Alleghany mountain range, 

 in its passage across central Pennsylvania from Maryland 

 to Luzerne county in this state; and if so, it forms one 

 of the most interesting features in American geology. 

 Much remains to be be done ere this supposition is con- 

 firmed in its contemplated extent : at present I shall 

 only state, as the basis upon which the opinion is founded, 

 that I have traced this line of fracture running for the 

 space of one hundred and fifty miles, equidistant from 

 the Alleghany mountains. 



Below Newport on the Juniata, and at Montgomery's 

 Ferry on the Susquehanna, a break occurs in the ar- 

 rangement of the strata, which extensively influences the 

 physical features of this district. Here then we discover 

 a second anticlinal line traversing the Juniata and Sus- 

 quehanna in a S. E. course, parallel with the Alleghany 

 mountain. To the north of this line numerous grau- 

 wacke rocks, gritstones, coal shales, and carboniferous 

 sandstones of the transition class, conglomerates and va- 

 riously coloured shales, chiefly those of a chocolate colour, 

 dip to the north at angles varying from 25 to 70°, for 

 a breadth of fifteen to twenty miles. To the south of 

 the same line of elevation another extensive suite of red 

 contorted shales, red and white sandstones and silicious 

 conglomerates, some of them perhaps identical with the 



