We pass many side canyons to-day that are dark, gloomy passages back into the heart of the rocks that form the plateau through which this canyon is cut. It rains again this afternoon. Scarcely do the first drops fall when little rills run down the walls. As the storm comes on, the little rills increase in size, until great streams are formed. Although the walls of the canyon are chiefly limestone, the adjacent country is of red sandstone; and now the waters, loaded with these sands, come down in rivers of bright red mud, leaping over the walls in innumerable cascades. It is plain now how these walls are polished in many places. At last the storm ceases and we go on. We have cut through the sandstones and limestones met in the upper part of the canyon, and through one great bed of marble a thousand feet in thickness. In this, great numbers of caves are hollowed out, and carvings are seen which suggest architectural forms, though on a scale so grand that architec- 239 powell-canyons-154.jpg NOONDAY REST IN MARBLE CANYON. 240 powell-canyons-155.jpg VIEW OF MARBLE CANYON FROM VERMILION CLIFFS. FROM THE GRAND TO THE LITTLE COLORADO. 241 tural terms belittle them. As this great bed forms a distinctive feature of the canyon, we call it Marble Canyon. It is a peculiar feature of these walls that many projections are set out into the river, as if the wall was buttressed for support. The walls themselves are half a mile high, and these buttresses are on a corresponding scale, jutting into the river scores of feet. In the recesses between these projections there are quiet bays, except at the foot of a rapid, when there are dancing eddies or whirlpools. Sometimes these alcoves have caves at the back, giving them the appearance of great depth. Then other caves are seen above, forming vast dome-shaped chambers. The walls and buttresses and chambers are all of marble. The river is now quiet; the canyon wider. Above, when the river is at its flood, the waters gorge up, so that the difference between high and low water mark is often 50 or even 70 feet, but here high-water mark is not more than 20 feet above the present stage of the river. Sometimes there is a narrow flood plain between the water and the wall. Here we first discover mesquite shrubs,--small trees with finely divided leaves and pods, somewhat like the locust. August 10.--Walls still higher; water swift again. We pass several broad, ragged canyons on our right, and up through these we catch glimpses of a forest-clad plateau, miles away to the west.