From the Devil's Slide to the mouth of Gardiner's River, twelve miles, the ground rises rapidly, passing from a dead level alkali plain, to a succession of plateaus covered slightly with a sterile soil. Evidences of volcanic action begin to be frequent: old craters converted into small lakes appear here and there, prettily fringed with vegetation, and covered with waterfowl. Scattered over the hills and through the valleys are numerous beautiful specimens of chalcedony and chips of obsidian. Many of the chalcedonies are geodes, in which are crystals of quartz; others contain opal in the centre and agate on the exterior; and still others have on the outside attached crystals of calcite. [Illustration] CHAPTER V. HOT SPRINGS OF GARDINER'S RIVER. Ten miles above the Devil's Slide, Gardiner's River, a mountain torrent twenty yards wide, cuts through a deep and gloomy gorge and enters the Yellowstone at the lower end of the Third Cañon. At this point the Yellowstone shrinks to half its usual size, losing itself among huge granite boulders, which choke up the stream and create alternate pools and rapids, crowded with trout. Worn into fantastic forms by the washing water, these immense rock masses give an aspect of peculiar wildness to the scenery. But the crowning wonder of this region is the group of hot springs on the slope of a mountain, four miles up the valley of Gardiner's River. The first expedition passed on without seeing them, but they could not escape the vigilance of the scientific company that followed.