THE MOUNTAIN. 91 



subsiding. The axes or arcs of the waves or wrinkles of the 

 rocks flatten out, and the strata show a tendency to assume 

 a horizontal position, approaching the quiet basin of the 

 centre of the continent. These gentler undulations retain 

 the general features of the abrupt eastern axes, that is, 

 they run in lines northeast and southwest, and preserve 

 their usual parallelism, and the relationship of the inclina- 

 tion of strata on the different sides of the axes. The two 

 great natural agents which give external geology and geo- 

 graphy to a country, namely, the deep subterranean or up- 

 heaving, and the superficial disintegrating and abrading 

 forces, have very clearly acted with much less intensity in 

 this region. The dips of the strata do not change often, 

 and the inclination of the rocks is never great, whilst the 

 fracturing and grinding of the strata and the sweeping 

 force of currents appear to have acted with much less 

 violence, and consequently, the destruction of the valuable 

 contents of this region has been prevented, over any con- 

 siderable extent, It is thus that the coal and iron of this 

 highly-gifted portion of the earth has been saved from de- 

 struction. Instead of wide-sweeping valleys of denudation, 

 such as we are presented with in the southeastern part of 

 the State, destroying and carrying to the rebuilding of new 

 continents vast quantities of mineral matter, we have small 

 narrow valleys and ravines, natural excavations as it were, 

 designed to bring into man's power the immeasurable wealth 

 of the rocks below. And here, in the small, as in the largest 

 thing that is, the wisdom and perfection of the Universe is 

 revealed. By this apparently accidental distribution of the* 

 surface into hill and hollow there is the most perfect access 

 to the mineral contents of the region ; and a large and com- 

 prehensive view of the geological structure of the north- 

 western half of the State presents an extensive basin, or 

 rather, the termination of an immense basin which extends 

 southwestwardly from the northern border of Pennsylvania, 

 almost to the centre of Alabama. This coal field, re- 

 markable for its vast extent, continues uninterruptedly from 



