PLEISTOCENE LOAMY DEPOSITS. 157 



area, and a great thickness, and it is little wonder that geologists, 

 whose theories of the origin of loss have been based chiefly upon 

 the phenomena presented by that deposit in the larger valleys 

 of Central Europe, should have held the view that loss is some- 

 thing quite by itself, having little or no connection with the 

 other Pleistocene accumulations with which it is associated. 

 But, as we have seen, in Belgium, and more especially in 

 Northern France, it loses much of its typical character, and this 

 is still better exemplified in the valleys and low grounds of the 

 south of England, where the loss-beds are composed in large 

 measure of brick-earth, in which sand, and even gravel, are 

 frequently intercalated. In short, the volume and composition 

 of the loss-beds are directly related to the extent of the drainage- 

 areas in which these deposits occur, and to the geological cha- 

 racter of the rocks from the degradation of which they have 

 been derived. 



Great as is the extent of area in Central and Western 

 Europe, which is covered by loss and brick-earth, it is yet 

 inconsiderable when compared with the vast tracts which in 

 Southern Bussia are clothed with the " Tchernozem " or black- 

 earth — an accumulation which occupies the same geological 

 horizon as the loss, and the origin of which is undoubtedly 

 closely bound up with that of the former. The black-earth 

 extends over the Steppes and low-lying plateaux that border on 

 the Black Sea, the Sea of Asov, and the depressed area to the 

 north of the Caspian, with a breadth from north to south of 

 from 200 or 300 to nearly 700 miles. It may be said to con- 

 tinue with little interruption from the regions watered by the 

 Pruth and the Dniester to the foothills of the Ural Mountains, 

 between Ufa and Orenburg, thus comprising an area of not less 

 than 500,000 square miles. Throughout this wide tract the 

 black-earth shows a singularly uniform character. Like the 

 loss of Central Europe, it has an extremely fine texture, and is 

 usually devoid of well-marked stratification. It varies in colour 

 from dark brown to black, and in thickness from a foot or two 

 up to twenty, and occasionally, it is said, even to sixty feet. 



