GEOLOGY. 449 



ROCKS OF THE BLUE RIDGE. 



As regards the crystalline rocks of the southern part of the Appala- 

 chian belt, J. B. Elliott has described several sections from the great 

 'alley along the border of Georgia, Tennessee, and the Carolinas. He 

 adopts the notions advanced by Bradley and some others as to the 

 °aleozoic age of these crystalline rocks. The Ocoee and theKnox groups 

 ,»f Safford, which include the Taconian and parts of the succeeding 

 'Jambriau, are supposed by Elliott to form, in a inetamorphio condition, 

 the great gneissic, micaceous, aud hornblendic belt of the Blue Bidge. 

 Phe view here resuscitated is not sustained by any new facts. The rocks 

 )f this region, as seen and described by the writer, in northwestern 

 G-eorgia, are pre-Cambrian schists, chiefly of Montalban age, with over- 

 ling Taconian quartzites, slates, and marbles, the age and relation of 

 #hich were long ago correctly pointed out by Lieber in South Carolina. 

 Che hypothesis of Bradley has no other argument in its support than 

 :hat deduced from apparent stratigraphical succession, which is as value- 

 less and misleading here as farther north along the same mountain-belt 

 n the Alps, in Wales, or in the Scottish Highlands, in all of which 

 "egious the fallacy of the metamorphic hypothesis and the pre-Cam- 

 H'ian age of the crystalline schists is now established. 



The recent studies of Fontaine in Virginia are important in this con- 

 aection as showing the relation of the crystalline rocks of the Blue Bidge 

 to the base of the Paleozoic series. In the interval of about sixty miles 

 between Turk's Gap and Balcony Falls he finds three groups of rocks. 

 The oldest, referred by him to the Laurentiau, is described as consist- 

 ing chiefly of coarse heavy-bedded granitoid gneisses, destitute of mica, 

 and containing a small amount of hornblende, which is not well defined. 

 Associated with and overlying these are massive bedded rocks, in which 

 hornblende predominates, with a triclinic feldspar and some magnesian 

 mica, doubtfully referred by him to the same series. The second group, 

 called by him Huronian, includes chloritic, argillaceous, and hydro-mi- 

 caceous schists, becoming epidotic, and passing into massive beds de- 

 scribed as felsitic in character, often concretionary and amgydaloidal. 

 This group abounds in copper, both native and in sulphuretted forms. 

 The third group, recognized by Fontaine as the Primal series of Bogers, 

 has here a thickness of about 2,400 feet, and consists essentially of shales, 

 flags, sandstones, and conglomerates. In its upper fourth is found a great 

 mass of quartzite, carrying the Scolithus typical of this series in Penn- 

 sylvania and elsewhere. Beneath it are intercalated quartzite beds, 

 sometimes conglomerate, and holding pebbles of the ancient gneiss. The 

 basal conglomerate, of unequal thickness, varies in composition with 

 that of the adjacent Eozoic rock, of which it is chiefly composed ; the peb- 

 bles being in some cases derived from the Laurentian gneisses and in 

 others from the Huronian schists. These basal beds are infiltrated with 

 quartz and chlorite, and in some cases are only distinguished from the 

 underlying Huronian schists, from which they were derived, by thepres- 

 H. Mis. 69 29 



