OF THE APPALACHIAN CHAIN. 487 



of the valley, though still often inverted, are not always so, the 

 flexures being less abrupt, and sometimes of the steep normal 

 type. Thus, in New Jersey, in the tract chiefly occupied by the 

 lower Appalachian limestone, the troughs become somewhat 

 open, and admit long, narrow, synclinal belts of the next superior 

 division, the great slate mass of the Hudson river. As we cross 

 this division northwestward, beyond the valley, the flexures soon 

 grow ^-ery gentle, and, as a consequence, the same rocks spread 

 themselves out over very wide tracts, imparting to both the ge- 

 ology and topography a comparatively monotonous character. 

 In all these conditions of flexure in this division, we detect the 

 proofs of a less energetic uplifting and bending force, when com- 

 pared with that which operated on the contiguous straight belts, 

 situated to the north and south, where the close and oblique pli- 

 cations fill the valley, and wiiere the steep normal flexures range 

 further across the chain. 



3. Susquehanna Division. Here the obliquely folded flexure 

 is the prevalent one throughout the great valley, giving a general 

 southeasterly direction to the dip. This inversion extends even to 

 some distance northwest of the valley, so as to reach the first an- 

 thracite basin, in the middle or widest portion of which a south- 

 erly dip very generally prevails. The flexures or axes of this 

 division occupy a very broad belt of country, extending from 

 Lancaster county, across to the northern line of Pennsylvania, a 

 space of one huncbed and fifty miles. 



4. Juniata Division. In this region, the strata are generally 

 inverted, throughout the whole breadth of the South Mountain 

 and the great valley. The principal anticlinal flexures of the 

 Middle Mountain-belt, are remarkable for their great height and 

 steepness, and for the frequency with which they bring almost 

 the lowest of the Appalachian formations to the surface. These 

 features, with the unusual breadth of the belt, across which the 

 disturbances of the strata extend, would seem to show, that the 

 forces producing the axes of this region were of unusual energy. 



5. Potomac Division. This belt is remarkable for the sti-aight- 

 ness of its principal axes, and for the beautiful manner in which 

 it exhibits the general laws of gradation in the flexures. Upon 



