Climb these 500 feet and you stand on the cliff sandstone. A terrace appears, and sometimes a wall of terraces set with alcoves of marvelous structure. Climb to the summit of this alcove sandstone--700 feet--and you stand at the foot of the red wall limestone. Sometimes this stands in two, three, or four Cyclopean steps--a mighty stairway. Oftener the red wall stands in a vertical cliff 1,600 feet high. It is the most conspicuous feature of the grand facade and imparts its chief characteristic. All below is but a foundation for it; all above, but an entablature and sky-line of gable, tower, pinnacle, and spire. It is not a plain, unbroken wall, but is broken into vast amphitheaters, often miles abound, between great angular salients. The amphitheaters also are broken into great niches that are sometimes vast chambers and sometimes royal arches 500 or 1,000 feet in height. 384 powell-canyons-247.jpg BOUNDED INWARD CURVES AND PROJECTING CUSPS OF THE WALLS. THE GRAND CANYON. 385 Over the red wall limestone, with its amphitheaters, chambers, niches, and royal arches--a climb of 1,600 feet--is the banded sandstone, the entablature over the niched and columned marble, an adamantine molding 800 feet in thickness, stretching along the walls of the canyon through hundreds of miles. This banded sandstone has massive strata separated by friable shales. The massive strata are the horizontal elements in the entablature, but the intervening shales are carved with a beautiful fretwork of vertical forms, the sculpture of the rills. The massive sandstones are white, gray, blue, and purple, but the shales are a brilliant red; thus variously colored bands of massive rock are separated by bands of vertically carved shales of a brilliant hue. On these highly colored beds the tower limestone is found, 1,000 feet in height. Everywhere this is carved into towers, minarets, and domes, gray and cold, golden and warm, alabaster and pure, in wonderful variety.