Density of population in piedmont belts.
The piedmont boundary also divides two areas of contrasted density of population. Mountain regions are, as a rule, more sparsely settled than plains. The piedmont is normally a transition region in this respect; but where high mountains rise as climatic islands of adequate water supply out of desert and steppes, they concentrate on their lower slopes all the sedentary population, making their piedmonts zones of greatest density. Low mountains in arid regions become centers of population; here their barrier nature vanishes. In the Sudanese state of Darfur, the Marra Mountains are the district best watered and most thickly populated. Nowhere higher than 6000 feet (1850 meters), they afford running water at 4000 feet elevation and water pools in the sandy beds of their wadis at 3200 feet. Below this, water disappears from the surface, and can be found only in wells whose depth and scarcity increase with distance from the central mountains.[1194] The neighboring kingdom of Wadai shows similar conditions and effects.[1195] In the heart of Australia, where utter desert reigns, the Macdonnell Ranges form the nucleus of the northern area occupied by the Arunta tribe of natives; farther north the Murchison Range, usually abounding in water-holes, is the center and stronghold of the Warramunga tribe.[1196]
Mineral wealth or waterpower in the mountains serves to collect an urban and industrial population along their rim, as we see it about the base of the Erz Mountains in Saxony, the Riesen range in Silesia, the coal-bearing Pennine Mountains of northwestern England, and the highlands of southern Wales, all which piedmont zones show a density of over 150 to the square kilometer (385 to the square mile). Hence the original Swiss Confederation, which included only the mountain cantons of Schwyz, Uri and Unterwalden, was greatly strengthened by the accession of the piedmont cantons of Lucerne, Zurich, Zug and Bern in the early fourteenth century, as later by St. Gall, Aargau and Geneva. These marginal cantons to-day show a density of population exceeding 385 to the square mile, and rising to 1356 in the canton of Geneva.
Piedmont towns and roads.
Piedmont belts tend strongly towards urban development, even where rural settlement is sparse. Sparsity of population and paucity of towns within the mountains cause main of traffic to keep outside the highlands, but close enough to their base to tap their trade at every valley outlet. On the alluvial fans or plains of these valley outlets, where mountain and piedmont road intersect, towns grow up. Some of them develop into cities, when they command transverse routes of communication quite across the highlands. The ancient Via Aemilia traced the northern base of the Apennines from Ariminum on the Adriatic to Dertona at the foot of the Ligurian range back of Genoa, and connected a long line of Roman colonies. The modern railroad follows almost exactly the course of the old Roman road,[1197] while a transverse line southward across the Apennines, following an ancient highway over the Poretta Pass to the Arno Valley, has maintained the old preëminence of Bologna. A line of towns, connected by highways or railroads, according to the economic development of the section, defines the bases of the Pyrenees, Alps, Jura, Apennines, Harz, Vosges, Elburz and numerous other ranges. Along the Elburz piedmont runs the imperial road of Persia from Tabriz through Teheran to Meshed. In arid regions these piedmont roads are an unfailing feature, but their towns shrink to rural settlements, except at the junction of transmontane routes.
Piedmont termini of transmontane routes.
Piedmont cities draw their support from plain, mountain and transmontane region, relying chiefly on the fertile soil of the level country to feed their large populations. Sometimes they hug the foot of the mountains, as Bologna, Verona, Bergamo, Zurich, Denver and Pittsburg do; sometimes, like Milan, Turin, and Munich, they drop down into the plain, but keep the mountains in sight. They flourish in proportion to their local resources, in which mineral wealth is particularly important, and to the number and practicability of their transmontane connections. Hence they often receive their stamp from the mountains behind them as well as from the bordering plain. The St. Gotthard route is flanked by Lucerne on the north and Milan on the south. The Brenner has its urban outlets at Munich and Verona. Narbonne and Barcelona form the termini of the route over the eastern Pyrenees; Toulouse commands the less used central passes, and Bayonne the western. Tiflis is situated in the great mountain trough connecting the Black Sea and the Caspian; but over the Caucasus by the Pass of Dariel come the influences which make it a Russian town. Peshawar, situated in the mountain angle of the Punjab, depends more upon the Khaibar Pass and its connections thereby with Central Asia than upon the plains of the Indus; its population, in appearance and composition nearly as much Central Asiatic as Indian, is engaged in traffic between the Punjab and the whole trans-Hindu Kush country.[1198]