of intercourse, retarded development and poverty of the choicest habitable areas.  This is one disadvantage of South Africa, emphasized farther by a poor coastline.  The Pacific face of Australia would gain vastly in historical importance, if the drop from the highlands to the ocean were stretched out into a broad slope, like that which links our Atlantic coastal plain with the Appalachian highlands.  There each river valley shows three characteristic anthropo-geographical sub-divisions—­the active seaports and tide-water tillage of its lower course, the contrasted agriculture of its hilly course, the upland farms, waterpower industries and mines of its headstream valleys, each landscape giving its population distinctive characteristics.  The same natural features, with the same effect upon human activities and population, appear in the long seaward slopes of France, Germany and northern Italy.

[Sidenote:  Piedmont belts as boundary zones.]

At the base of the mountains themselves, where the bold relief begins, is always a piedmont zone of hilly surface but gentler grade, at whose inner or upland edge every phase of the historical movement receives a marked check.  Here is a typical geographical boundary, physical and human.  It shifts slightly in different periods, according to the growing density of population in the plains below and improved technique in industry and road-making.  It is often both an ethnic and cultural boundary, because at the rim of the mountains the geologic and economic character of the country changes.[1189] The expanding peoples of the plains spread over the piedmont so far as it offers familiar and comparatively favorable geographic conditions, scatter their settlements along the base of the mountains, and here fix their political frontier for a time, though later they may advance it to the crest of the ridge, in order to secure a more scientific boundary.  The civilized population of the broad Indus Valley spread westward up the western highlands, only so far as the shelving slopes of the clay and conglomerate foothills, which constitute the piedmont of the Suleiman and Kirthar Mountains, afforded conditions for their crops.  Thus from the Arabian Sea for 600 miles north to the Gomal River, the political frontier of India was defined by the line of relief dividing the limestone mountains from the alluvial plain, the marauding Baluch and Afghan hill tribes from the patient farmers of the Sind.[1190] This line remained the border of India from pre-British days till the recent annexation of Baluchistan.

These piedmont boundaries are most clearly defined in point of race and civilization, where superior peoples from the lowlands are found expanding at the cost of retarded mountain folk.  Romans and Rhaetians once met along a line skirting the foot of the eastern Alps, as Russians to-day along the base of the Caucasus adjoin the territories of the heterogeneous tribes occupying that mountain area.[1191] [See map page