As already noticed, the country about the mouth of Gardiner's River is desolate and gloomy. The hill-slopes are covered with sage brush, the constant sign of arid soil, and grass is scarce. This is the first poor camping-place on the route. The cañon being impassable, the trail passes to the right, crossing several high mountain-spurs, over which the way is much obstructed by fallen timber, and reaching at last a high rolling plateau. This elevated tract is about thirty miles in extent, with a general declivity to the north. Its surface is an undulating prairie, dotted with groves of pine and aspen. Numerous lakes are scattered throughout its whole extent, and great numbers of springs, which flow down the slopes, are lost in the volume of the Yellowstone. The river breaks through this plateau in a winding cañon over 2,000 feet in depth--the middle cañon of the Yellowstone rolling over volcanic boulders in some places, and in others forming still pools of seemingly fathomless depth. At one point it dashes to and fro, lashed to a white foam on its rocky bed; at another, where a deep basin occurs in the channel, it subsides into a crystal mirror. Numerous small cascades are seen tumbling from the rocky walls at different points and the river appears from the lofty summits a mere ribbon of foam in the immeasurable distance below. Standing on the brink of the chasm the heavy roaring of the imprisoned river comes to the ear only in a sort of hollow, hungry growl, scarcely audible from the depths. Lofty pines on the bank of the stream "dwindle to shrubs in dizziness of distance." Everything beneath, says Lieut. Doane, has a weird and deceptive appearance. The water does not look like water, but like oil. Numerous fish-hawks are seen busily plying their vocation, sailing high above the waters, and yet a thousand feet below the spectator. In the clefts of the rocks down, hundreds of feet down, bald eagles have their eyries, from which one can see them swooping still farther into the depths to rob the ospreys of their hard-earned trout. It is grand, gloomy, and terrible; a solitude peopled with fantastic ideas; an empire of shadows and of turmoil. The plateau formation is of lava, generally in horizontal layers, as it cooled in a surface flow, yet upheaved in many places into wave-like undulations. Occasionally granite shafts protrude through the strata, forming landmarks of picturesque form. Like dark icebergs stranded in an ocean of green, they rise high above the tops of the trees in wooded districts, or stand out grim and solid on the grassy expanse of the prairies. [Illustration: EXTINCT GEYSER, EAST FORK OF THE YELLOWSTONE.]