lowland of
England also can be differentiated economically and historically chiefly
according to differences of underlying rocks, Carboniferous, Triassic,
Jurassic, chalk, boulder clays, and alluvium, which also coincide often
with slight variations of relief.[1045] In Russia the contrast between the
glaciated surface of the north and the Black Mould belt of the south
makes the only natural divisions of that vast country, unless we
distinguish also the arid southeastern steppes on the basis of a purely
climatic difference. [See map page 484.]

The broad coastal plain of our South Atlantic States contains only low
reliefs; but it is diversified by several soil belts, which exert a
definite control over the industries of the inhabitants, and thereby
over the distribution of the negro population. In Georgia, for instance,
the rich alluvial soil of the swampy coast is devoted to the culture of
rice and sea-island cotton, and contains over 60 per cent. of negroes in
its population. This belt, which is only 25 miles wide, is succeeded
inland by a broader zone of sandy pine barrens, where the proportion of
negroes drops to only 20 or 30 per cent. of the total. Yet further
inland is another fertile belt, devoted chiefly to the cultivation of
upland cotton and harboring from 35 to over 60 per cent. of negroes in
its population.[1046] Alabama shows a similar stratification of soils and
population from north to south over its level surface. Along the
northern border of the state the cereal belt coincides with the deep
calcareous soil of the Tennessee River Valley, where negroes constitute
from 35 to 60 per cent. of the inhabitants. Next comes the mineral belt,
covering the low foot-hills of the Appalachian Mountains. It contains
the densest population of the state, less than 17 per cent. of which is
negro. South of this is the broad cotton belt of various rich soils,
chiefly deep black loam of the river bottoms, which stretches east and
west across the state and includes over 60 per cent. of negroes in its
population. This is succeeded by the low, coastal timber belt, marked by
a decline in the quality of the soil and the proportion of negro
inhabitants.[1047]

[Sidenote: Value of slight elevations.]

In the dead level of extensive plains even slight elevations are seized
upon for special uses, or acquire peculiar significance. The Kurgans or
burial mounds of the prehistoric inhabitants of Russia, often twenty to
fifty feet hi