The cause of this great region of the plains spreading out treeless and devoid of vegetation has been the subject of extravagant _conjecture_, and some queer _theories_ have been advanced. Some persons think that it was once covered with trees and plants, but was swept over by fire, which so thoroughly destroyed all seed and roots that there was nothing left to sprout; hence the broad, clear range. All persons who have _been_ upon the plains will scout all such theories, for nothing will grow there if planted. The physical condition of this great track is but the reasonable effect of the working of natural laws. _Rain_ is all that is required to make the desert beam and blossom like the beautiful valleys of the _states_, though of course it would take some years to turn the dry sands into soil. No well-informed person wonders why _Sahara_ is a desert; and though the region of the plains is visited with a few more little showers, and the surface is not so sandy, yet the _principle_ is the _same_. What falls from the clouds is but that which arises by the process of evaporation from the waters below. The evaporation from our little _inland_ waters is very _limited_, that as _rain_ it would amount to very few and feeble showers. The great oceans, seas, and gulfs that fringe the continent are the mighty reservoirs from which rise our dews and refreshing showers; and wherever their moisture is not carried, the effect is invariably that of which the great deserts of the world, and the mighty plains of America, bear testimony to-day. In this case, the distance is so great from the waters north and east that all the moisture is lost before it reaches the prairie-land. It is also a great way from the gulf, and to the west the _mountain ranges_ rear their cold summits aloof to extract the dampness from the Pacific breeze. Hence, so long as the broad, open waters roll in their present channels, and the hills and valleys remain, the American plains will divide the East from the West, and their dry surface will glitter in the bright, burning sun. It is, nevertheless, an excellent stock-range; and judging from the mighty herds annually shipped from this great field, it appears a _necessary_ pasture-land for the _world_. It appears that the all-designing Providence, in the creation, prepared for the contingencies of mankind, and adapted this region to its present use, as well as the mountain-sides to the glittering diamonds and rusty ores.