232 POPULAR SCIENCE MONTHLY. 



valley which passes gradually into the great trans- Yolgian steppes. 

 Much interesting discussion as to the peculiar soils of the steppes and 

 their relations to geology and to tree-growth can only be alluded 

 to. In proceeding eastward the great Permian formation, so named 

 by Murchison, begins to appear, forming a broad band or zone stretch- 

 ing along the western base of the Urals. The " tchernozem " or 

 surface soil of the steppes rests upon successively older rocks as 

 the route passes northeastward from the Volga toward the moun- 

 tains. Beneath it appear more or less of the Caspian deposits, partly 

 overlaid and partly connected with the " terrace clay " of the Quater- 

 nary. The underlying rocks are in succession Cretaceous, Yol- 

 gian, Jurassic, and Permian, as this wide area is traversed. Permo- 

 carboniferous and Carboniferous rocks are met on entering the 

 Urals, the lower members of each appearing successively, and, when 

 the folds of the mountains are fully reached, a great body of De- 

 vonian. 



Between Samara and Oufa, as the steppes rise, the country pre- 

 sents an aspect which Professor Nikitin observes as strikingly like 

 the eroded plateau regions of the western United States. This is 

 particularly well marked in the valley of the Dioma River, where 

 high level regions of nearly horizontal stratified sediments have been 

 worn down along all the drainage lines into scarped and picturesque 

 heights, with broad, flat areas of intervening watershed as we 

 should call it, a country of caiions, mesas, and " mauvaises terres." 



The rocks of this region are principally Permian, but the Russian 

 geologists are not fully agreed as to the details. A great body of 

 limestones, marls, and sandstones, definitely of upper Permian age 

 (" Zechstein "), lies between two distinct series of " marines irisees " 

 red and variegated marls. The lower of these is undisputed (the 

 " Rothliegender "), but the upper is regarded by some as also true 

 Permian, and by others as transitional to the Triassic. For this 

 upper series the name " Etage Tartarien " is employed. 



It is interesting to note how much more continuous the geological 

 succession appears to be here than in the west of Europe. The 

 recognition of the Permian itself, as a whole, was an immense ad- 

 vance in this direction; and now we can almost trace it downward 

 through the Permo-carboniferous and upward through the Tar- 

 tarian, connecting the Palaeozoic and the Mesozoic continuously. In 

 the same way, and in almost the same region, the Yolgian series 

 appears to unite the Jurassic with the Cretaceous. 



From Oufa to and through the southern Urals the description 

 is taken up by Professor Tschernitschew. The structure of the 

 Urals bears some marked resemblances to that of our Appalachians; 

 the general course is much the same, north-northeast to south-south- 



