Stevenson.] ZZU [jan. 21, 



that the reports of that survey are so rare ; since the map prepared by 

 Prof. Rogers and published in "The Resources of Virginia," shows that 

 the structure was admirably worked out. The faults are clearly shown on 

 that map, and the distinction between the limestones of the Lower Carbonif- 

 erous and the Lower Silurian was determined accurately, though at that time 

 there was little aside from physical characters to depend on for identifica- 

 tion. When it is remembered that the region was even more thinly settled 

 forty years ago than it is now, one may not refrain from acknowledging 

 the skill and patience with which the structure was worked out at that 

 early day. 



To obtain the material given in this memoir, one section was followed 

 from Black mountain almost directly to Bristol ; a second from Penning- 

 ton's gap in Stone mountain to the Tennessee line by way of Estillville 

 and Moccasin gap through Clinch mountains ; shorter sections were fol- 

 lowed across Moccasin and Copper ridges ; while several of the faults were 

 followed for from ten to twenty miles. Necessarily, many interesting 

 details were neglected, and some points of importance were left undecided, 

 as the object of the reconnaissance was purely economic. 



No map worthy of the name exists, and that accompanying this memoir 

 is based on the old State map, made in 1835. Some gross topographical 

 errors have been corrected partially ; others remain, which interfere 

 seriously with a proper presentation of the geology ; but to correct these 

 would involve a complete reconstruction of the whole. 



I. General Structure of the Area. 



The structure is monoclinal, and the prevailing dip is toward the south- 

 east. The one exception is in the area between Black mountain and the 

 summit of Powell mountain, where, as will be shown, a cracked anticlinal 

 exists. In passing from Black mountain to the Valley of Virginia at 

 Bristol, one crosses 



1. The fault of Poor ValUy ridge. 



2. The Wallen valley fault. 



3. The Pattonsville fault. 



4. The Hunter valley fault, or Clinch river uplift of Lesley. 



5. The fault of Copper creek. 



6. The fault of the North Fork of Holston. 



7. The fault of Walker mountain. 



Black mountain is a rude mass, which owes its origin solely to erosion. 

 It is the dividing ridge between the waters of the Cumberland and those of 

 Powell and Clinch rivers. Its course is irregular but bears westward and 

 southward until, at a little way west from Pennington's gap in Stone 

 mountain, it unites with the latter ridge. The only rocks' exposed in this 

 mountain are those of the Coal Measures, and their dip is northward, or 

 north north-west. Toward Stone mountain, the dip suddenly increases 

 until in that ridge it becomes almost, and at some places, wholly vertical. 



Stone mountain is a bold narrow ridge with a N. 67° E. course, which 



