560 W. F. Hume — Notes on Russian Geology. 



underlies this phenomenon. Not having visited the southern reaches 

 of these streams it would be unwise to start a theory without actual 

 evidence to support it. 



At the present day there is still some apparent tendency to 

 Southern advance on the part of the Eussian Continent. The 

 eruptive activities in the Taman peninsula are causing elevations 

 which may eventually close the entry to the Sea of Azov altogether. 

 Meanwhile the Don is pouring its mud-laden waters into the 

 northern end of the same sea. Shipping, that within the memory of 

 men now living, could come right up to the town of Taganrog, has 

 now got to anchor 16 miles outside in the roadstead. Von Baer 

 indeed, held that the Azov Sea is undergoing a gradual elevation. 



Similarly the N. part of the Caspian Sea is slowly retiring or dry- 

 ing up, and the great rivers, as the Volga and Dnieper, are becoming 

 silted up. This fact was strongly impressed on my mind while 

 our steamer was fast aground for about twelve hours on a sand- 

 bank in the latter river, while the peasants apparently standing 

 in mid-stream were only up to their waists in water. 



The following may possibly represent the sequence of events: — 

 I. The Loess particles may be originally derived from the finely 

 ground material resulting from the wearing of the subjacent beds 

 by the ice-sheet. II. The same have been deposited in tundra-like 

 depressions under the influence of slowly-moving waters, or by the 

 action of rivers in flood. III. This deposit under more temperate 

 conditions dried up, and was then suitable material for the redistri- 

 butive action of the wind. 



The redistributive actions are still at work, but denudation is 

 rapidly proceeding, giving rise to the broken ground which lends 

 such special features of beauty and even of wildness to such towns 

 as Kieff', Poltava, and Kharkoff. Floods every year transfer Loess 

 to the lower grounds, whereas wind on the contrary tends to carry 

 it higher in a vertical direction. Plants, with their penetrating roots, 

 steppe-rats tarantulas, and worms all help to break up the porous 

 soil, and thus assists the continuance of the redistribution. 



The Loess country is, as has been already stated, one of the chief 

 wheat growing districts of the world. It satisfies in every particular 

 the conditions which Berthelot demanded as being favourable for 

 the fixation of Nitrogen (Comp. Kendus, cvii. 20, 852, etc.), viz. 

 a soil of sandy and clayey nature, which admits of free access of 

 air and is not too moist. Also it must have been rich in potash and 

 poor in nitrogen. 



Of course the weathering of the granite rocks on the W. of the 

 Dnieper must be constantly adding fresh materials, w4nch, under the 

 action of the wind, will form part, or has helped to form a part, of 

 the Loess as it is met with in those areas. Indeed, I have already 

 mentioned in this connection that in the neighbourhood of the 

 Archfean rocks the Loess appears to be much richer in micaceous 

 materials. 



The belief in an ice-sheet and the traces of its action are so wide- 

 spread that I need scarcely ofier an excuse for using it so freely 

 as a primary cause in the above article. 



