Low mesas, dry, treeless, stretch back from the brink of the canyon, often showing smooth surfaces of naked, solid rock. In some places the country rock is composed of marls, and here the surface is a bed of loose, disintegrated material through which one walks as in a bed of ashes. Often these marls are richly colored and variegated. In other places the country rock is a loose sandstone, the disintegration of which has left broad stretches of drifting sand, white, golden, and vermilion. Where this sandstone is a conglomerate, a paving of pebbles has been left,--a mosaic of many colors, polished by the drifting sands and glistening in the sunlight. After the canyons, the most remarkable features of the country are the long lines of cliffs. These are bold escarpments scores or hundreds of miles in length,--great geographic steps, often hundreds or thousands of feet in altitude, presenting steep faces of rock, often vertical. Having climbed one of these steps, you may descend by a gentle, sometimes imperceptible, slope to the foot of another. They thus present a series of terraces, the steps of which are well-defined escarpments of rock. The lateral extension of such a line of cliffs is usually very irregular; sharp salients are projected on the plains below, and deep recesses are cut into the terraces above. Intermittent streams coming 33 powell-canyons-13.jpg A ZUÑI COURT. 34 powell-canyons-14.jpg ADOBE CHURCH--ZUÑI. THE VALLEY OF THE COLORADO. 35 down the cliffs have cut many canyons or canyon valleys, by which the traveler may pass from the plain below to the terrace above. By these gigantic stairways he may ascend to high plateaus, covered with forests of pine and fir. The region is further diversified by short ranges of eruptive mountains. A vast system of fissures--huge cracks in the rocks to the depths below--extends across the country. From these crevices floods of lava have poured, covering mesas and table-lands with sheets of black basalt. The expiring energies of these volcanic agencies have piled up huge cinder cones that stand along the fissures, red, brown, and black, naked of vegetation, and conspicuous landmarks, set as they are in contrast to the bright, variegated rocks of sedimentary origin.