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interest, and at the same time renders the task of such an examina- 

 tion laborious and difficult. 



Whatever may be our view of the origin of the truly crystalline 

 rocks which occasionally occur throughout this region, numerous 

 sectional examinations, which have been made with the view of 

 solving some of the difficulties connected with its geology, have 

 combined in establishing this interesting conclusion, that by far the 

 largest portion of its surface is occupied by rocks which do not be- 

 long to the primary system, while they have, at the same time, 

 served to display the modifying effects of igneous agents, as 

 manifested in the changed structure of many of these rocks, on a 

 scale of wonderful variety and extent. 



Early in the present report, allusion was made to the prevailing 

 errors on the subject of the true geological character of this region, 

 inclusive of the Blue Ridge ; and enough has already been stated in 

 regard to the structure of the region, to satisfy the enlightened 

 geologist of the entire impropriety of the designation of primary 

 which it has heretofore uniformly received. The further particulars 

 about to be given relative to some of its rocks, chiefly those of 

 economical value, will serve still more clearly to evince the inac- 

 curacy which has hitherto prevailed with regard to the limits of the 

 great geological subdivisions of the state, as well as to display the 

 practically valuable results which are linked with an investigation 

 which at first view appears to be purely scientific in its character. 



The rocks of the South-west mountain and its prolongations, and 

 of the country within a few miles on either side, will first be de- 

 scribed, after which some account will be given of those lying more 

 to the west, and in particular of some portions of the Blue Ridge. 



Pursuing the line indicated in the profile, after leaving the bed of 

 limestone, already referred to, we meet with slates and schists in 

 some places of a micaceous and talcose, and in others of a silicious 

 nature, and so friable as to be of but little use in building ; com- 

 prising occasional beds of a denser texture, and more resembling 

 roofing slate. This brings us to the greenish and dark blue argil- 

 laceous sandstone of which Carter's mountain, as well as much of 

 the region on its eastern and western flanks, principally consists. 

 Beds of gray and yellow sandstone occasionally present themselves 

 among the darker rock, and these are uniformly of a coarser texture, 

 and in many cases are rapidly decomposed by exposure to the air 

 and weather. Quarries of the dark greenish and bluish rock have 



