EXCURSIONS OF THE GEOLOGICAL CONGRESS. 233 



west, and the principal character is that of a series of parallel folds, 

 with the anticlinal crests eroded into longitudinal valleys, so that 

 each axis of elevation produces two parallel lines of heights. Simi- 

 larly, too, the disturbance increases from the west eastward, and 

 metamorphic and intrusive rocks appear and attain a great develop- 

 ment toward the Asiatic side. Beyond, moreover, forming a sepa- 

 rated though intimately connected portion of the system, are the 

 Ilmen Mountains and others that align with them, highly meta- 

 morphic, much intruded, and exceedingly rich in mineral treasures. 

 These recall our Blue Ridge range in its geographical relation to 

 the Alleghanies, though their connection with the Urals is much 

 closer geologically. Finally, the Ural range, like our true Appa- 

 lachians, is monogenetic i. e., the product of a single period of ele- 

 vation. 



The body of the southern Urals consists of Devonian and Car- 

 boniferous beds, much inclined. The latter are principally lime- 

 stones, while the former, largely also calcareous above, become more 

 fragmental lower down. The succession of stages is very regular 

 in each, and is discussed at length. In the lower Devonian (Her- 

 cynian) occurs a hard and heavy sandstone, which by its resistance 

 to erosion forms generally the crests of the parallel ridges. This 

 sandstone not only passes into quartzite, but becomes at times mi- 

 caceous and takes on a distinctly metamorphic habit. Professor 

 Tschernitschew gives a clear and detailed account of the gradual 

 passage of this sandstone into various kinds of micaceous, talcose, 

 and chloritic schists. In the eastern Urals intrusive rocks appear 

 more and more, mainly granites and diabases. Of these there are 

 again many particulars given, and especially interesting accounts 

 of the contact phenomena, where these dikes and veins have trav- 

 ersed the sedimentary rocks and produced local alteration. 



In regard to Quaternary deposits the remarkable fact is brought 

 out that there are no definite traces of glaciation in the Ural Moun- 

 tains south of latitude 61. All the surface deposits are local, 

 either the work of streams or from the decomposition of rocks in 

 place, after the manner of our " southern drift." For this latter 

 process and its results the words " eluvion " and " depots eluviales " 

 are used in these treatises in distinction from material removed and 

 redistributed by flowing water a convenient and desirable term. 

 Most of the gold placers of the Urals are of these kinds alluvial in 

 some places and eluvial in others, but not glacial. In some cases 

 the auriferous gravel and sand can be traced downward almost di- 

 rectly into the disintegrating quartz of an outcropping vein. 



The main Urals are rich in iron ores, chiefly hematite and spathic 

 iron; in the Ilmen range the ore is magnetite and occurs in a differ- 



TOL. LII. 19 



