Note 1119 — Chapter XIV · —Plains, Steppes And Deserts

Such supplementary agriculture usually shifts with the nomad group. But where high mountains border rainless tracts, their piedmont districts regularly develop permanent cultivation. Here periodic rains or melting snows on the ranges fill the drainage streams, whose inundation often converts their alluvial banks into ready-made fields. The reliability of the water supply anchors here the winter villages of the nomads, which become centers of a limited agriculture, while the pasture lands beyond the irrigated strips support his flocks and herds. Where the piedmont of the Kuen Lun Mountains draws a zone of vegetation around the southern rim of the Takla Makan Desert, Mongol shepherds raise some wheat, maize and melons as an adjunct to their cattle and sheep; but their tillage is often rendered intermittent by the salinity of the irrigating streams.1119 Along the base of the Tian Shan Mountains, the felt yurt of the Gobi nomad gives place to Turki houses with wheat and rice fields, and orchards of various fruits; so that the whole piedmont highway from Hami to Yarkand presents an alternation of desert and oasis settlement.1120 Even the heart of arid Arabia shows fertile oases under cultivation where the lofty Nejd Plateau, with its rain-gathering peaks over five thousand feet high, varies its wide pastures with well tilled valleys abounding in grain fields and date-palm groves.1121 Along the whole Saharan slope of the Atlas piedmont a series of parallel wadis and, farther out in the desert, a zone of artesian wells, sunk to the underground bed of hidden drainage streams from the same range, form oases which are the seat of permanent agriculture and more or less settled populations. The Saharan highlands of Tibesti, whose mountains rise to 8,300 feet, condense a little rain and permit the Tibbus to raise some grain and dates in the narrow valleys.1122