The. Black Earth. 305 



of S. Enssia, in which he rejects the aeolian theory, and advocates 

 that of glacial origin. 



He considers the deposit under several heads : 



1. The Loess may be of glacial, marine, lacustro-fluviatile, eluvial, 

 or diluvial origin. 



2. The fine-grained Loess of the Poltava or Nijni-Novgorod type, 

 of uniform structure throughout its thickness (except where a few 

 small erratic blocks are present in its lower portions), and containing 

 terrestrial or marsh-living organisms only ; this Loess, covering the 

 watersheds and ancient slopes, ^'s of exdnsively glacial origin, and 

 represents the finer constituents of the glacial mud deposited over 

 a country already covered with vegetation, and inhabited by the 

 typical rodents of the steppes (as the Alactaga, the Spermophilus, 

 the Arctomys, and the Lagomys) ; by the Mammoth and Ehiuoceros, 

 and occasionally by the Beaver. 



3. A similar Loess occurs sporadically as little islands throughout 

 the whole of the districts bearing traces of glaciation, sometimes in 

 the inferior sands containing erratic blocks, and sometimes in the 

 northern brown clays ; but they become less frequent as we approach 

 the sources of the Russo-Scandinavian glacier. 



The Glacial Loess occurs principally (1) at the S. and S.E. limits 

 of the glacier itself, and (2) in that part of the open country 

 immediately contiguous to its probable boundary. In the first case 

 it may cover all the watersheds ; in the second it will only be in 

 those districts where the absolute height is inferior to that of the 

 most elevated points of the neighbourhood occupied by deposits of 

 erratic blocks. For example, in the government of Poltava the 

 maximum height of these deposits above sea-level is 210 metres, 

 consequently in the whole of the lower basin of the Dnieper it 

 should only occur at heights less than 210 metres. 



4. One of the most characteristic peculiarities of the Glacial Loess 

 is the presence of the dark-grey glacial mud, forming a definite 

 but interrupted layer, frequently attaining a thickness of over two 

 metres. It is distributed in patches, containing many large grains 

 of quartz, and sometimes calcareous inclusions. The humus per- 

 centage is 3. 



5. In the eastern wing of the glacier, that of the Don, the Loess 

 is a stratified, coarse, and somewhat porous clay, of a brown-grey 

 colour, but its origin is similar to that previously mentioned. 



6. The typical Loess is absent, and cannot in general exist on the 

 very ancient portions of the earth's crust. Exceptions occur along 

 the whole of the Dnieper Valley, at the exterior limits of the 

 glacier, and on the littoral of the Sea of Azov, where marine are 

 interstratified with glacial deposits ; Loess possessing the type 

 characteristics also occurs in the south of Poland. 



7. The Asiatic Loess is in all probability partly glacial in origin, 

 but may be also eluvial, diluvial, or alluvial ; only in isolated 

 regions, occupying ravines of greater or less depth, will it be 

 distinctly of aeolian derivation. Prof. Dokoutchaieif would also 

 remove the Loess of W. Europe from the seolian category. 



DECADE IT. VOL. I. — NO. VII. 20 



