1897.] 



NATURAL SCIENCES OP PHILADELPHIA. 



413 



development of its limestones and marls in innumerable swellings or 

 lumps of various sizes from a few inches to a few feet in diameter, 

 which on examination prove to consist either of concentric cabbage- 

 like layers, or of irregular foliations like the bent leaves of a book. 



The immensely important conditions which follow from the 

 acceptation of the Russian Survey's determination of the relations 

 of the rocks forming the Oural-Taou, or main chain of the Oural, 

 makes it desirable to consider it a little more attentively. 



The Oural-Taou, or main chain, and water-divide of those moun- 

 tains is formed of crystalline schistose rocks, which are in intimate 

 connection with deposits of indisputable paleozoic age, and which 

 themselves are nothing but modified paleozoic rocks. This is the 

 terse summing up of the thesis [L. G., Ill, 12], and the argument is 

 contained in the ideal section (ib., p. 11), in which the lower Devonic 

 member is shown to be a quartzite lying in a synclinal between 

 schists and limestones above and below ; and the lower of these lime- 

 stones is stated to contain no fossils by which its age can be definitely 

 ascertained in the northern Oural region. But in the South Ouralsit 

 contains an extensive fauna described by Tschernischew. 



if.ir. 



Section from +he 7L\a<r{\ qn "ho +he Avn\r\r 



(from Livret" GuideUE . pit) 



Fig. 1. 

 Df Limestone. Upper stage of the Lower Devonic. 

 DJ g Quartzose sandstone and schists. 

 D\ c Limestones. 

 M Metamorphic schists and quartzites. 



The section representing the views of the Russian Geological 

 Survey as to the structure of the Oural chain is seen in L. G., Ill, 

 p. 11, and is thus described by M. Tschernischew: — 



" The most instructive section of the lower Devonic of the south 

 Ourals extends south of the line of railway, from the chain of 



