I 



DRA IN A GE MODIFICA TIONS 677 



local suhsklcnccs. The remaining areas of these rocks seem to 

 range themseU'cs in two approximately parallel lines. The 

 westernmost line consists of the Dan River" and Danville areas, 

 Scottsville and Barboursville areas, and the great New York- 

 Virginia area stretching in an almost continuous line from Ger- 

 mantown. North Carolina to Stony Point, New York. This is 

 the direct continuation of the Chattahoochee drainage line, and, 

 strangely enough, it is apparently continued to the northward 

 by the valley of the Hudson River and Lake Champlain. The 

 easternmost line, consisting of the Wadesboro and Deep River 

 areas, the Richmond area and the Connecticut area, roughly par- 

 allels the first, and it has a northward extension in the Connect- 

 icut River Valley. Whether or not it ever had a southwest- 

 ward extension similar to the parallel line cannot now be deter- 

 mined, for post-Triassic erosion and sedimentation have removed 

 all traces of such streams if they ever existed. 



These parallel lines are everywhere marked by stream valleys 

 or areas of deposition, therefore by our criteria they should 

 mark the axes of parallel depressions. These depressions seem 

 to have reached their maximum near the center of the line, for 

 in this portion the sediments probably formed a continuous 

 sheet, indicating that the old land surface had sunk entirely 

 below water level. This maximum submergence appears to have 

 been along a cross axis, or one extending in a northwest and 

 southeast direction ; and to this cross depression is probably due 

 the location of the Susquehanna River, the largest and most 

 vigorous of the central Atlantic streams. Judging from the 

 direction of the flow of the streams located along the longitudi- 

 nal axis, it seems probable that the depression reached a mini- 

 mum at the southern line of North Carolina, for at that point 

 the waters divide toward the southwest and the northeast. 



If our interpretation is correct, these are some of the oldest 

 streams in the United States. With the one exception of the 

 upper portion of Savannah River, which formerly belonged to the 



' The names of the various areas of Triassic rocks are taken from Correlation 

 Papers — The Newark System, by I. C. Russell, Bulletin No. 85, United States Geo- 

 logical -Survey. 



