38 Feather stonhaugh's Geological Report. 



slates and other rocks known as the gold region of the United 

 States. 



Wherever the geological student finds the strata thrown out 

 of the horizontal line, and dipping in any direction, he may ? 

 with few exceptions, enumerate such beds amongst the forma- 

 tions hitherto described, the old red sandstone inclusive. Few 



county, Virginia, it consists of the members of the lower Cambrian rocks, very much 

 studded with points ef native copper, with a belt of porphyritic granite running 

 at its eastern base. In other parts of this chain I have observed quartzose sand- 

 stones and conglomerates prevailing, of undoubted aqueous origin ; whilst in some 

 districts, slates of a green quartzose character contain, imbedded and mixed up and 

 alternating with them, true porphyritic masses. This admixture of rocks, to which 

 different origins are attributed, appeared to me to justify a designation for this 

 chain which expressed, in some degree, its predominant mineral character. The 

 only proper use which those who write on this subject, at present, can make of 

 theoretical terms, is to give the greatest degree of perspicuity to what they say. 

 The terms primary and primordial are, undoubtedly, always very properly applied 

 to the lower rocks, to which an igneous origin has been attributed ; but may fairly 

 be extended to any series of rocks constituting a great geographical boundary, to 

 which they give a predominating character, especially at a period when the term 

 Transition is passing into disuse, and leaves the term Primary freed from theoret- 

 ical views, to class all the rocks in below the secondary order. I have felt 

 myself authorized to do this by the example of one of the most distinguished men 

 of this age. Professor Sedgwick, of Cambridge, England, in his " Introduction 

 to the general structure of the Cambrian mountains," (Transactions of the Geo- 

 logical Society of London, vol. 4, part 1, page 66,) observes: " I beMeve, how- 

 ever, that there is a broad mineralogical distinction between the primary stratified 

 rocks (including under that term all stratified rocks inferior to the old red sand- 

 stone) and the secondary/' Professor Phillips, also, the able and experienced 

 Professor of Geology in King's College, London, has, in his Guide to Geology, 

 page 19, classed all the rocks beneath the old red sandstone as " Primary strata," 

 adding, " It is usual to class the upper systems under the title of Transition strata,, 

 and to confine the name of Primary to the mica, schist, and gneiss systems." And 

 at page 72, he says : " Thus, for example, of the extinct crustaceous animals, call- 

 ed Trilobites, the far greater portion of those found in England belongs to the 

 primary strata. They ako characterize the primary system of North America." 

 In fact, he generally speaks of the beds beneath the carboniferous group as the 

 " fossiliferous primary strata," and, at page 124, distinctly includes all the beds of 

 whatever kind, constituting what, on account of its geographical situation princi- 

 pally, I had named " Atlantic primary chain," in the following passage. " The 

 older strata are now very generally called primary, and an indefinite upper group 

 or portion of them is,, by many geologists,, called the Transition series, a& marking 



