466 Reports and Proceedings — 



Abstracts of Papers read before the Geological Section of 

 THE British Association at Montreal, August, 1884. 



1. — Pennsylvania before and after the Elevation of the 

 Appalachian Mountains. 



By Prof. E. W. Claypole, B.A., B.Sc, F.G.S. Lond. 



THE paper, of which the following notes are an abstract, is in- 

 tended as an attempt to handle, in a necessarily imperfect 

 manner, and only to first approximations, a difficult but important 

 and interesting geological subject. The method of treatment is, in 

 the writer's opinion, one that has not hitherto been employed for 

 the same purpose. 



The object in view is to form some estimate, as near to the truth 

 as possible, of the amount of compression or shortening produced at 

 the surface by the corrugation of the upper layers of the coast into 

 mountain chains, with especial reference to the American Atlantic 

 seaboard. 



In order to confine the paper within due limits, certain proposi- 

 tions must be taken as proved. The principal of these are : 



1. That central contraction has developed tangential pressure 



in the crust. 



2. That the tangential pressure has produced crumpling of 



the crust. 



3. That to this crumpling are due long ranges of mountains. 



4. That the Appalachian Mountains came into being in this 



manner in the later portion of the Palaeozoic era. 



Thesfi admitted, the conclusion necessarily follows that during the 

 formation of the Appalachian Mountains a considerable contraction 

 of the crumpled area ensued, in a direction at right angles to that 

 of the chain. 



The following points constitute the main features of the paper : 



1. Short account of the great ranges of Pennsylvania, in plan 



and section, with diagrams. 



2. Situation and account of the line of section adopted. 



3. Limitation of the field to a consideration of eleven great 



ranges — 

 Blue Mountains 

 Bower Mountains 

 Conecoclieague Mountains 

 Tuscarora Mountains 

 W. Shade Mountains 

 Black Loff Mountains 



Blue Eidge Mountains 

 Jack's Mountain 

 Standing Stone Mountains 

 Tussey Mountains 

 Bald Eagle Mountains 



4. Discussion of the diff'erent parts of this section — 



(a) The Mountain Region. 

 \b) The Cumberland Valley. 



5. Attempt to estimate or measure the curved line of the 



crumpled Upper Silurian (Medina) sandstone. 



6. Inference that the sixty-five miles of the line of section 



