404 



PALAEOZOIC TIME. 



Mauch Chunk region, Pennsylvania. The great coal bed is folded 

 and doubled on itself, and part of the enclosing strata are nearly 

 vertical. In fig. 620 (by Rogers), from Trevorton, Pa., the folding 

 is of a more gentle kind ; eight coal seams are contained in this 



Fig. 620. 



Section of the Coal measures half a mile west of Trevorton Gap, Pa. 



section, each of the dark lines representing one. These are exam- 

 ples of the condition of the whole anthracite region. The patches 

 into which it is divided, as shown on the map, p. 323, illustrate 

 other effects of the foldings ; for the whole, in all probability, was 

 originally one great area, continuous with that of western Penn- 

 sylvania. 



The sections represented in figs. 621, 622, illustrate the flexures 

 of the Palseozoic rocks, showing that the whole participated in 



Fig. 621. 



Section on the Schuylkill, Pa. ; P. Pottsville, on the Coal measures. 



the system. Fig. 621 (by Lesley) is a section from the Schuyl- 

 kill along by Pottsville : the formations included in it embrace 



Fie. 622. 



VVLYJY M 



ectiori from the Great North to the Little North Mountain through Bore Springs, Va. ; t, t, 

 position of thermal springs. 



from the Potsdam sandstone (2) to the Coal formation (14); the 

 numbers indicate the formations. The section in fig. 622 (by 

 Rogers) extends from the Great North to the Little North Moun- 

 tain through the Bore Springs, in Virginia: it has been partly ex- 



