The Llano, together with its southward extension, having the same characteristics and known as the Edwards plateau, is bordered on the west by the deep and broad valley of the southward-flowing Pecos River, and on the north by the equally deep and broad valley carved in the plateau country by the eastward-flowing Canadian River. The eastward slope of the surfaces of the two plateaus is continued throughout the region bordering them on the east all the way to the shore of the Gulf of Mexico. The streams originating on the eastern border of the eastward sloping plateaus and flowing to the Gulf of Mexico, represented at the present time by the Colorado (of Texas), the Brazos, Trinity, and Red Rivers, extended their trunks by head-water corrasion and developed numerous branches so long as the rainfall was sufficient to maintain a surface drainage. But as the streams were lengthened they cut farther and farther westward and into a region that became drier and drier, until finally they reached a land in which all of the scanty rain that fell was absorbed by the thirsty soil. The drainage from this higher and drier region is subterranean, and reaches the head waters of the streams to the eastward to a considerable extent as springs. The streams which lowered the country to the eastward of the Llano developed many branches, some of which were extended westward into the drier plateau country in such a manner as to give the eastern margin of the remaining upland a scalloped and irregular border. In travelling westward up the courses of the rivers of eastern Texas, one passes from a low region of old topography to one where the head branches of the streams flow in canyons, and the relief has the ruggedness of youth; on gaining the western border of the belt of country having surface streams one ascends to the smooth surface of the high plateau, which is young as regards stream development, although in years older than the country with a deeply eroded surface to the eastward. The Llano and Edwards plateau present us with examples of perpetuated topographic youthfulness. The Llano, although dreaded by early explorers and shunned so far as possible even by experienced plainsmen, on account of a lack of water, has in recent years become more favourably known. It is crossed at present by two railroads. Water has been found beneath the surface in numerous localities, and the desert-like region now bids fair to become a favourable cattle-raising country. It is not to be expected, however, that all the glowing predictions which have been published concerning this and neighbouring table-lands will be more than partially fulfilled through the use of the subsurface waters.