this vicinity entirely composed of the hot-spring deposits, at least nine-tenths silica, appearing snowy-white in the distance; one of the walls is 175 feet high, and another about 70 feet. They are now covered to a greater or less extent with pines. Steam is constantly issuing from vents around the base and from the sides of these hills. There is one lake 100 by 300 yards, with a number of bubbling and boiling springs rising to the surface. Near the shore is one of the sieve-springs, with a great number of small perforations, from which the water bubbles up with a simmering noise; temperature, 188°. This group really forms one of the great ruins." A short day's march from Hell-broth Spring brings the traveller to a little stream flowing into the Yellowstone, between the upper and the lower fall. From its rapid and tumultuous flow, the first explorers called it Cascade Creek. Just before its union with the Yellowstone it traverses a gloomy gorge cut through a kind of volcanic sandstone, largely made up of fragments of obsidian and other igneous rocks cemented with volcanic ash. This rock is worn by the water into so many fantastic shapes and cavernous recesses, that--with their usual poverty of invention and tartarean taste--the first observers straightway gave the uncanny channel over to the Prince of Darkness, and dubbed it the Devil's Den. A mile below this gorge the stream flows over a series of ledges, making a cascade as beautiful as its previous course has been weird and ugly. There is first a fall of five feet, which is immediately succeeded by another of fifteen, into a pool as clear as amber, nestled beneath overarching rocks. Here the stream lingers as if half reluctant to continue its course, then gracefully emerges from the grotto, and, veiling the rocks down an abrupt descent of eighty-four feet, passes rapidly on to the Yellowstone. For a wonder, this charming fall has received a corresponding name--Crystal Cascade. An infinite variety of volcanic specimens, quartz, feldspar, mica, granites, lavas, basalts, composite crystals--in fact, everything, from asbestos to obsidian, is represented by fragments in the bed of this stream. [Illustration: THE DEVIL'S DEN.] At the foot of the gorge and on the margin of the Yellowstone stands a high promontory of concretionary lava, literally filled with volcanic butternuts. Many of these are loose, and can be taken out of the rock with the hand; broken open, they are invariably hollow, and lined with minute quartz crystals of various tints. This rare formation occurs frequently in the great basin. CHAPTER VIII. THE GRAND CAÑON AND THE FALLS.