406 



PALEOZOIC TIME. 



claiming absolute accuracy, it gives a correct general idea of the 

 number and positions of the folds in this part of the Appalachian 

 region. 



Fig. 624. 



Map of Pennsylvania, showing the positions of the axes of the folds in the strata. 



The following are some of the most important facts established 

 with regard to these Appalachian flexures : — 



1. They occupy the whole Appalachian and Eastern-border regions of 

 the continent nearly or quite to the Atlantic Ocean. 



2. They are parallel with the general course of the mountains, 

 and nearly with the Atlantic coast. 



3. They are most crowded and most abrupt over the part of the 

 regions which is towards the ocean, — that is, the southeast side 

 (figs. 622, 623). 



4. The steepest slope of a fold is that which faces the northwest, 

 or away from the ocean (figs. 621-623). 



