STRATIGRAPHICAL AND ORUOENIO EELATIONS. 11 



close of the Carboniferous period. This table-land is well exhibited in the 

 plateau of central Tennessee, but is most strikingly shown in the degraded 

 remnant of its northern part, known as the Catskill Mountains. 



It has not yet been sufficiently recognized that to the east of tne old 

 -Appalachian axis there was a great series of mountain ranges, now obliter- 

 ated, which extended from the southern part of North Carolina along the 

 Atlantic coast as far as Eastport, Maine. The reason why this portion of 

 the system has been neglected is found in the fact that the structures which 

 belong to it are peculiar in form and have been so far worn away that they 

 present no considerable topographical reliefs. The region has the general 

 character of a country which has been bx^ought near to base-level, and the 

 determination of the position of the ridges and furrows can be made only 

 from the attitudes of the rocks. In fact, in the present state of our knowl- 

 edge of this section of the country, only a few of the old troughs are 

 recognizable and the position of the folds is not well made out. 



Beginning on the south, we find the southernmost of these folds, so far 

 as they have been recognized, in the Dan Eiver Basin of North Carolina. 

 Farther north, the Kings Mountain district appears to indicate the seat 

 of another folding, a part of the rocks involved in the movement being so 

 hard that they have not yet been completely eroded. In the Richmond 

 coal field an extensive series of beds, |)i*obably of Triassic or Rhsetic age, 

 indicates the presence of another considerable basin, which has something 

 like the area, depth, and general form of the Narragansett downfold. 

 From studies of the Richmond Basin, made at various times, I have 

 becomes convinced that the depth of the depression in its central parts 

 probably exceeds 3,000 feet, and may be twice that amount, and that, in 

 part at least, it is separated from the sea by an area of uplift which is now 

 worn down to its granitic base. 



To the north of the James River Valley in eastern Virginia the Triassic 

 rocks are again found involved in relatively deep, broad troughs, the forms 

 of which are not yet well made out. There are probably several of these 

 troughs, some of which contain ancient stratified rocks of undetermined 

 age that may belong in pre-Paleozoic time. From the Potomac River 

 northward, owing to the mantle of Cretaceous and Tertiary waste, we have 

 no distinct indications of this series of foldings until, in New Jersey, we 

 again find the Trias involved in troughs. East of the Hudson the broad 



