Note 1189 — Chapter XV · —Mountain Barriers And Their Passes

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.