Slates).* The Appalachian Mountains on its western side are Middle and 

 . and Devonian formations. West ol 



Upper Silur 

 high escarpi 



Scientific Intellige\ 



ts western side are W 



the long 

 f the Carboniferous formation, forming the mountain 

 plateau ot western Pennsylvania, Western Virginia, Eastern Kentucky, 

 Central Tennessee, and Northern Alabama. The escarpment of this vast 

 plateau, facing the east, and overlooking the Appalachian ranges, with 

 their narrow, parallel, interval valleys, is the so-called Backbone Alle- 

 ghany Mountain, beginning at Catskill on the Hudson, and ending in 

 Alabama. The northern portion of this plateau is drained eastward by 

 the branches of the Susquehanna, and westward by the branches of the 

 Alleghany and Monongahela Rivers. All the waters of Middle Pennsyl- 

 vani, Maryland, and Northern and Middle Virginia flow from the foot of 

 this escarpment towards the Atlantic, breaking successively through the 

 parallel Appalachian ridges of the subcarboniferous formations. The 

 ■»aters of the Tennessee Rn-er head also at the eastern foot of this escarp- 

 ment, and flow along its base for several hundred miles southwestward, 

 before they turn west at Chattanooga, and break through its southern 

 extremity, to make their great circuit through Alabama, Western Tennes- 

 see, and Kentucky to the Ohio River near its mouth. But in the middle 

 of tlie region, namely, in Southern Virginia, its normal drainage is re- 

 versed. The New River heads in the Blue Range, crosses the Great Val- 

 ley westward, breaks into (not out of) the Appalachians, striking the ^- 

 carpment in its face, and Howing directly through and across it (as the 

 Great Kanawha) through Western Virginia into the Ohio, 



The cause of this phenomenon is to be found in a chansfe of structure 

 t this line. Most of the valleys and mountains north 



JSiew Jersey are unbroken anticlinals and synclinals. Most of the valleys 

 Alabama, are monoclinals, 



^rdnia and Eastern Tennes- 



hwest, is fractured in parallel s 



1 five to SIX 



._.. ^_ „„^ angle (dipping soutneasi; 



that at each fault the upper edge of one strip (with its Carboniferous 

 rocks) abuts against the bottom or Lower Silurian edge of the strip next 

 to it. As the Palfeozaie system, thus revealed (on edge) between any two 

 of these faults, contains two massive sandrock formations, No. IV, Middle 

 Silurian, and No, X, Upper Devouian, there occur necessarily between 

 each pair of faults a pair of parallel moutains. The Palaeozoic zone, 

 therefore, included between the Great Valley and the Backbone escar^^ 

 ment. is oprnniprl W ns manv T^nirc ^f ,^orull..l mountains as there are 

 straight lines at neaHy 

 3 run with reniArkable 



--.^^,-^ J o.v.., ... « uuuu.... .1 .wo hundred miles, and are 



lly cut off, eiiher by short cross faults, or by slight angular chanff^ 

 he courses of the great faults. Thus we get an explanation ot tn 



