THE GREAT PLAINS. 'Phis is the name usually given to the lands which rise gradually from the prairies to the eastern base of the Rocky Moun tains. But the altitude of these lands is such that they might he called with propriety a pla teau. From altitudes of about 1000 feet along the Missouri River in Kansas mud Nebraska, they rise to heights of 5000 to 6000 feet at the foot of the western mountains. In general this rise is imperceptibly gradual, but its continuity is sometimes interrupted by escarpments, and the easterly (lowing rivers have incised shallow val leys upon the region. The strata are little dis turbed and thus the country resembles the prairie region, but the underlying hells are geologically younger and are overlain in many areas by large bodies of waste, which in part may have been deposited in lakes and in parts was no doubt distributed by torrents from the mountains. Climatic causes have also made the region different in aspect from the prairies. The plains are semi-arid in the east and truly arid in the west, and are therefore but sparsely clad with vegetation. Forests are thus infre
quent, the herbaceous vegetation is sparse and has the character of the desert, and agriculture as one goes west is dependent on irrigation. Over large areas the water supply for this purpose is deficient, and grazing is the only remaining re source. This region is a vast one, having the east and west limits already given, and reaching from central Texas to the northern border of the country, where it merges into the great Western plains of Canada. In the north the most promi nent break in the plains is the Black Tiflis moun taM area. Here an elevated mass of ancient rocks protrudes through the younger strata, giv ing a region of rugged relief, hard rocks, mines, and forests. ln the Black (Tills region. in much of the western Dakotas, and in Montana and western Nebraska. are the Bad Lands (q.v.).