191^.] STEVENSON— THE, FORMATION OF COAL BEDS. 547 



•changed his course and ascended the river 253 miles to Pavlodav. 

 The numerous natural sections had the same structure and com- 

 position as at Omsk, except that the pebbles increased in number and 

 size, becoming as large as a walnut within 100 miles. The section 

 of the deposit at Pavlodav is 



Feet. 



1. Soil. 



2. Stratified red sand, with lines of small gravel 20 



3. Light colored sandy silt 8 



4. Coarse, clean sand, with lines of small pebbles and one line of 



coarse pebbles 15 



5. Clayey silt, not laminated; fragments of bed rock in the lower 



half 6 



resting on magnesian limestone. The river at this place flowed on 

 the edge of an alluvial plain 6 miles wide. He crossed at Pavlodav 

 and travelled southwest seeking the source of the pebbles. At 

 about 60 miles from that city, his wheel jolted on the first stone 

 encountered during the ride of nearly 1,000 miles. Thencefor- 

 ward, angular fragments of quartz were abundant and within a 

 short distance he reached exposures of crystalline rocks. Belt was 

 inclined to believe that ice had impounded the fresh water into a 

 lake, but Ansted had asked, whence came the water to make the 

 freshwater lake of nearly 3,000,000 square miles, in which the steppe 

 deposits were laid down, and also, if there had been the lake, what 

 has become of the water. Ramsay^*^ conceived that, if we could 

 imagine the vast flat territory of Siberia with its mighty rivers facing 

 south to a sub-tropical sea, we would have something like the 

 Carboniferous. Coal beds do not indicate old lakes but continental 

 areas, through which rivers meandered. 



Reference was made on an earlier page to Kuntze's^*^ description 

 of conditions in the Paraguayan region, but other writers have 

 gone into more detail respecting some features requiring considera- 

 tion here. Church^^° says that a vast area in the Plata region is 



*^° G. E. Church, " Argentine Geography and the Ancient Pampean Sea," 

 Rep. Brit. Assoc. Adv. Set., for 1898, pp. 932-934. 



14S 



A. C. Ramsay, " Physical Geology and Geography of Great Britain," 

 5th ed., London, 1878, p. 139. 



' O. Kuntze, " Geogenetische Beitrage," 1895, PP- 67, 68. 



149 , 



