springs and ponds of water deeply embosomed in the cliffs. From the southern escarpment of this plateau the great Colorado Plateau rises by a comparatively gentle acclivity, and Marble Canyon starts with walls but a few score feet in height until they reach an altitude of about 5,000 feet. On the way the channel is cut into beds of rock of lower geologic horizon, or greater geologic age. These rocks are sandstones and limestones. Some beds are very hard, others are soft and friable. The friable rocks wash out and the harder rocks remain projecting from the walls, so that every wall presents a set of stony shelves. These shelves rise along the wall toward the south as new shelves set in from below.
In addition to this shelving structure the walls are terraced and the cliffs of the canyon are set back one upon the other. Then these canyon walls are interrupted by side streams which themselves have carved lateral canyons, some small, others large, but all deep. In these side gorges the scenery is varied and picturesque; deep clefts are seen here and there as you descend the river—clefts furnished with little streams along which mosses and other plants grow. At low water the floor of the great canyon is more or less exposed, and where it flows over limestone rocks beautiful marbles are seen in many colors; saffron, pink, and blue prevail. Sometimes a façade or wall appears rising vertically from the water for thousands of feet. At last the canyon abruptly ends in a confusion of hills beyond which rise towering cliffs, and the group of hills are nestled in the bottom of a valley-like region which is surrounded by cliffs more than a mile in altitude.
From here on for many miles the whole character of the canyon changes. First a dike appears; this is a wall of black basalt crossing the river; it is of lava thrust up from below through a huge crevice broken in the rock by earthquake agency. On the east the Little Colorado comes; here it is a river of salt water, and it derives its salt a few miles up the stream. The main Colorado flows along the eastern and southern wall, Climbing this for a few hundred feet you may look off toward the northwest and gaze at the cliffs of the Kaibab Plateau.
This is the point where we built a trail down a side canyon where Mr. Walcott was to make his winter residence and study of the region; it is very complicated and exhibits a vast series of unconformable rocks of high antiquity. These lower rocks are of many colors; in large part they are shales. The region, which appears to be composed of bright-colored hills washed naked by the rain, is,in fact, beset with a multitude of winding canyons with their own precipitous walls. It is a region of many canyons in the depths of the Grand Canyon itself.
In this beautiful region Mr. Walcott, reading the book of geology, lived in a summerland during all of a long winter while the cliffs above were covered with snow which prevented his egress to the world. His companions, three young Mormons, longing for a higher degree of civilization, gazed wistfully at the snow-clad barriers by which they were inclosed. One was a draughtsman, another a herder of his stock, and the third his cook, They afterward told me that it was a long winter of homesickness, and that months dragged away as years, but Mr. Walcott himself had the great book of geology to read, and to him it was a winter of delight.
A half dozen miles below the basaltic wall the river enters a channel carved in 800 or 1,000 feet of dark gneiss of very hard rock. Here the channel is narrow and very swift and beset with rapids and falls. On the south and16
