OF THE APPALACHIAN CHAIN. 515 



westward from the region of intrusive veins and dykes, which 

 has evidently been the quarter of extensive and violent actual dis- 

 ruptions of the crust. It moreover affords a reason for the striking 

 parallelism which prevails between the axes in every division of 

 the chain, and the veins and dykes in the corresponding tracts to 

 the southeast. In this rent and dislocated zone of country, begin- 

 ning with the chain of the Blue ridge, the incalculably numerous 

 and greatly extended dykes and veins that every where penetrate 

 and fill the altered and hypogene rocks, comprise, we believe, an 

 ample quantity of inwedged material, to balance the horizontal 

 contraction of the whole plicated chain. 



The mere fact of a regular gi*adation in the amount of flexure, 

 is of itself a proof, that the axes thus related had a common 

 source, while the dnection of this gradation, clearly establishes, 

 that the southeast was the quarter from whence the movement 

 proceeded. 



The views here entertained of the nature of the elevating action, 

 afford a satisfactory cause for the arrangement of the axes in 

 groups, since we have merely to imagine successive sets of pul- 

 sations of varying magnitude and momentum, to have followed 

 each other in the same general period of disturbance, and we are 

 supplied with a cause sufficient to produce all the diversity which 

 we behold in the distances and directions of the flexures. The 

 almost exact parallelism of these in each group, and the general 

 parallelism of all that enter into the same division of the chain, 

 are the necessary results of that wave-like movement in which we 

 conceive the axes to have originated ; and we confess ourselves at 

 a loss to imagine how any other action, but an undulation of the 

 crust, propagated in parallel lines, either straight or curving, could 

 give rise to this exti'aordinary feature in these enormously extended 

 anticlinal and synclinal lines. 



The curious facts connected with the curving form of the axes, 

 in certain districts, are likewise well accounted for by the hypoth- 

 esis. Of those divisions where they are convex to the northwest, 

 and where the curvature is generally so regular, we have merely 

 to suppose that the disturbance began with the production of the 

 axes of each adjoining division, that these terminated towards 



