The savant to whose tender mercies these disjecta membra have been committed, finds in the molluscan life the most recent types yet discovered in the American Tertiaries,—forms closely allied to existing Asiatic species. How and wherefore this lake dried up, and gave place to the present barren wilderness of sand and sage, is one of those profound conundrums of nature yet unguessed by geologists. From being a wide and beautiful expanse of water, edged by winding mountain-shores, with forest-clad slopes containing a fauna whose remains are now charming those light-minded fellows, the paleontologists, the scene has entirely changed, and a monotonous, blank desert spreads itself as far as the eye can reach. Only here and there, near the snowy mountain-tops, a bit of cool green contrasts refreshingly with the sterile uniformity of the plain. During the period of desiccation, perhaps in a measure accounting for it, a general flood of lava poured down from the mountains and deluged nearly the whole Snake Basin. The chief sources of this lava lay at the eastern edge, where subsequent erosion has failed to level several commanding groups of volcanic peaks. The three buttes and three tetons mark centres of flow. Remarkable features of the volcanic period were the sheets of basaltic lava which closed the eruptive era, and in thin, continuous layers overspread the plain for three hundred miles. The earlier flows extended farthest to the west. The ragged, broken terminations of the later sheets recede successively eastward, in a broad, gradual stairway; so that the present topography of the basin is a gently inclined field of basaltic lava, sinking to the west, and finally, by a series of terraced steps, descending to the level of lacustrine sand-rocks which mark the bottom of the ancient lake, and cover the plain westward into Oregon.
The head-waters of the Snake River, gathering snow-drainage from a considerable portion of the Rocky Mountains, find their way through a series of upland valleys to the eastern margin of the Snake plain, and there gathering in one main stream flow westward, occupying a gradually deepening cañon; a narrow, dark gorge, water-worn through the thin sheets of basalt, cutting down as it proceeds to the westward, until, in longitude 114° 20´, it has worn seven hundred feet into the lava. Several tributaries flowing through similar though less profound cañons join the Snake both north and south. From the days of Lewis, for whom this Snake or Shoshone River was originally named, up to the present day, rumors have been current of cataracts in the Snake cañon. It is curious to observe that all the earlier accounts estimate their height as six hundred feet, which is exactly the figure given by the first Jesuit observers of Niagara. That erratic amateur Indian, Catlin, actually visited these falls; and his account of them, while it entirely fails to give an adequate idea of their formation and grandeur, is nevertheless, in the main, truthful. Since the mining development of Idaho, several parties have visited and examined the Shoshone.
In October, 1868, with a small detachment of the United States Geological Survey of the 40th Parallel, the writer crossed Goose Creek Mountains, in northern Utah, and descended by the old Fort Boise road to the level of the Snake plain. A gray, opaque haze hung close to the ground, and shut out all distance. The monotony of sage-desert was overpowering. We would have given anything for a good outlook; but for three days the mist continued, and we were forced to amuse ourselves by chasing occasional antelopes.
The evening we camped on Rock Creek was signalized by a fierce wind from the northeast. It was a dry storm, which continued with tremendous fury through the night, dying away at daybreak, leaving the heavens brilliantly clear. We were breakfasting when the sun rose, and shortly afterward, mounting into the saddle, headed toward the cañon of the Shoshone. The air was cold and clear. The remotest mountain-peaks upon the horizon could be distinctly seen, and the forlorn details of their brown slopes stared at us as through a vacuum. A few miles in front the smooth surface of the plain was broken by a ragged, zigzag line of black, which marked the edge of the farther wall of the Snake cañon. A dull, throbbing sound greeted us. Its pulsations were deep, and seemed to proceed from the ground beneath our feet.
Leaving the cavalry to bring up the wagon, my two friends and I galloped on, and were quickly upon the edge of the cañon-wall. We looked down into a broad, circular excavation, three quarters of a mile in diameter, and nearly seven hundred feet deep. East and north, over the edges of the cañon, we looked across miles and miles of the Snake plain, far on to the blue boundary mountains. The wall of the gorge opposite us, like the cliff at our feet, sank in perpendicular bluffs nearly to the level of the river, the broad excavation being covered by rough piles of black lava and rounded domes of trachyte rock. We saw an horizon as level as the sea; a circling wall, whose sharp edges were here and there battlemented in huge, fortress-like masses; a broad river, smooth and unruffled, flowing quietly into the middle of the scene, and then plunging into a labyrinth of rocks, tumbling over a precipice two hundred feet high, and moving westward in a still, deep current, to disappear behind a black promontory. It was a strange, savage scene: a monotony of pale blue sky, olive and gray stretches of desert, frowning walls of jetty lava, deep beryl-green of river-stretches, reflecting, here and there, the intense solemnity of the cliffs, and in the centre a dazzling sheet of foam. In the early morning light the shadows of the cliffs were cast over half the basin, defining themselves in sharp outline here and there on the river. Upon the foam of the cataract one point of the rock cast a cobalt-blue shadow. Where the river flowed round the western promontory, it was wholly in shadow, and of a deep sea-green. A scanty growth of coniferous trees fringed the brink of the lower cliffs, overhanging the river. Dead barrenness is the whole sentiment of the scene. The mere suggestion of trees clinging here and there along the walls serves rather to heighten than to relieve the forbidding gloom of the place. Nor does the flashing whiteness, where the river tears itself among the rocky islands, or rolls in spray down the cliff, brighten the aspect. In contrast with its brilliancy, the rocks seem darker and more wild.
The descent of four hundred feet from our standpoint to the level of the river above the falls has to be made by a narrow, winding path, among rough ledges of lava. We were obliged to leave our wagon at the summit, and pack down the camp equipment and photographic apparatus upon carefully led mules. By midday we were comfortably camped on the margin of the left bank, just above the brink of the falls. My tent was pitched upon the edge of a cliff, directly overhanging the rapids. From my door I looked over the cataract, and, whenever the veil of mist was blown aside, could see for a mile down the river. The lower half of the cañon is excavated in a gray, porphyritic trachyte. It is over this material that the Snake falls. Above the brink the whole breadth of the river is broken by a dozen small trachyte islands, which the water has carved into fantastic forms, rounding some into low domes, sharpening others into mere pillars, and now and then wearing out deep caves. At the very brink of the fall a few twisted evergreens cling with their roots to the rock, and lean over the abyss of foam with something of that air of fatal fascination which is apt to take possession of men.
In plan the fall recurves up stream in a deep horseshoe, resembling the outline of Niagara. The total breadth is about seven hundred feet, and the greatest height of the single fall about one hundred and ninety. Among the islands above the brink are several beautiful cascades, where portions of the river pour over in lace-like forms. The whole mass of cataract is one ever-varying sheet of spray. In the early spring, when swollen by the rapidly melted snows, the river pours over with something like the grand volume of Niagara, but at the time of my visit it was wholly white foam. Here and there along the brink the underlying rock shows through, and among the islands shallow, green pools disclose the form of the underlying trachyte. Numberless rough shelves break the fall, but the volume is so great that they are only discovered by the glancing outward of the foam.
The river below the falls is very deep. The right bank sinks into the water in a clear, sharp precipice, but on the left side a narrow, pebbly beach extends along the foot of the cliff. From the top of the wall, at a point a quarter of a mile below the falls, a stream has gradually worn a little stairway: thick growths of evergreens have huddled together in this ravine.
By careful climbing we descended to the level of the river. The trachytes are very curiously worn in vertical forms. Here and there an obelisk, either wholly or half detached from the cañon-wall, juts out like a buttress. Farther down, these projecting masses stand like a row of columns upon the left bank. Above them, a solid capping of black lava reaches out to the edge, and overhangs the river in abrupt, black precipices. Wherever large fields of basalt have overflowed an earlier rock, and erosion has afterward laid it bare, there is found a strong tendency to fracture in vertical lines. The immense expansion of the upper surface from heat seems to cause deep fissures in the mass.
Under the influence of the cool shadow of cliffs and pine, and constant percolating of surface-waters, a rare fertility is developed in the ravines opening upon the cañon shore. A luxuriance of ferns and mosses, an almost tropical wealth of green leaves and velvety carpeting, line the banks. There are no rocks at the base of the fall. The sheet of foam plunges almost vertically into a dark, beryl-green, lake-like expanse of the river. Immense volumes of foam roll up from the cataract-base, and, whirling about in the eddying winds, rise often a thousand feet in the air. When the wind blows down the cañon a gray mist obscures the river for half a mile; and when, as is usually the case in the afternoon, the breezes blow eastward, the foam-cloud curls over the brink of the fall, and hangs like a veil over the upper river. On what conditions depends the height to which the foam-cloud rises from the base of the fall it is apparently impossible to determine. Without the slightest wind, the cloud of spray often rises several hundred feet above the cañon-wall, and again, with apparently the same conditions of river and atmosphere, it hardly reaches the brink. Incessant roar, reinforced by a thousand echoes, fills the cañon. Out of this monotone, from time to time, rise strange, wild sounds, and now and then may be heard a slow, measured beat, not unlike the recurring fall of breakers. From the white front of the cataract the eye constantly wanders up to the black, frowning parapet of lava. Angular bastions rise sharply from the general level of the wall, and here and there isolated blocks, profiling upon their sky line, strikingly recall barbette batteries. To goad one’s imagination up to the point of perpetually seeing resemblances of everything else in the forms of rocks is the most vulgar vice of travellers. To refuse to see the architectural suggestions upon the Snake cañon, however, is to administer a flat snub to one’s fancy. The whole edge of the cañon is deeply cleft in vertical crevasses. The actual brink is usually formed of irregular blocks and prisms of lava, poised upon their ends in an unstable equilibrium, ready to be tumbled over at the first leverage of the frost. Hardly an hour passes without the sudden boom of one of those rock-masses falling upon the ragged débris piles below.