1 Q9 



Kerr.] A - t} - i [April 4, 



is, that though the force he small, it has been active for a very long 

 period ; and moreover, it may he added, since these river valleys were 

 doubtless scooped out mainly, (as is apparent even from the above sec- 

 tion), during the (early part of the) drift or ice period, when the volume 

 and velocity of their currents were immeasurably greater than now, 

 the deflective force of these currents was far from infinitesimal in amount, 

 or insensible in aggregate effect. These river valleys were excavated 

 while the region was elevated more than one (probably several) hundred 

 feet above its present level, and afterwards silted up during the later 

 ages of the Ice Period, when it was sunk to a depth of more than 400 

 feet lower than now, and then re-excavated as the continent rose the 

 second time from the sea. At the close of the Tertiary, when the coast 

 was elevated so as to bring this territory above the waters of the Atlantic, 

 the surface was doubtless left comparatively level with a gentle slope 

 seaward ; and the rivers, in seeking their channels by the lines of quickest 

 descent, may be supposed to have divided it into belts whose drainage 

 surfaces north and south were about equal. But as their course was 

 over the surface of uncompacted sands, clays, &c, these currents, by 

 the incessant impact of their waters upon the right bank would gradually, 

 but more and more slowly, eat their way southward. Whenever an 

 obstacle was encountered in this southward movement, in the form of 

 resisting clays, compacted earths or projecting rocks, the course of the 

 river above would be thrown into a curve with its convexity to the 

 south. 



It is obvious that under similar conditions these phenomena must be 

 observable elsewhere, that is, in regions where wide level tracts of un- 

 consolidated earths have been traversed for long periods by strong river 

 currents, especially by the floods of Glacial and sub-glacial times. And 

 even in regions occupied by the older rocks the effects of this force of 

 the earth's rotation may manifest itself, for example, in latitudes where 

 the decomposition of the rocks more than keeps pace with the abrasive 

 and transporting power of the meteoric waters. The middle region 

 of North Carolina furnishes an illustration. Observant farmers who 

 have been long accustomed to haul their produce to South Carolina, 

 across the course of the principal streams, have asked me why they had 

 all the worst hills to ascend going to market and only moderate acclivities 

 returning. In this region the rocks are concealed by a thick covering of 

 earth, 30 to 50 feet and more, (resulting from their decomposition in 

 situ) ; so that the conditions being somewhat similar to those existing 

 near the coast, the topography may be supposed to have been affected 

 to some extent by the rotation. If this theory be valid, of course it will 

 receive confirmation from observations in other parts of the world where 

 the proper conditions coexist, "and if not, not." 



