On the summit of the great mound is one of a class I have called central springs; it is located on the highest point of the mound on which this great group belongs; has a crater twenty feet in diameter, very nearly quiescent, slightly bubbling, or boils near the centre, with a thin, elegant rim projecting over the spring, with the water rising within a few inches of the top. The continual but very moderate overflow of this spring, uniformly on every side, builds up slowly a broad-based mound, layer by layer, one-eighth to one-sixteenth of an inch thick. Looking down into these springs, you seem to be gazing into fathomless depths, while the bright blue of the water is unequalled even by the sea. There are a number of these marvellous central springs, with projecting rims carved with an intricate delicacy which of itself is a marvel; and as one ascends the mound and looks down into the wonderfully clear depths, the vision is unique. The great beauty of the prismatic colors depends much on the sunlight, but about the middle of the day, when the bright rays descend nearly vertically, and a slight breeze just makes a ripple on the surface, the colors exceed comparison; when the surface is calm there is one vast chaos of colors, dancing, as it were, like the colors of a kaleidoscope. As seen through this marvellous play of colors, the decorations on the sides of the basin are lighted up with a wild, weird beauty which wafts one at once into the land of enchantment; all the brilliant feats of fairies and genii in the "Arabian Nights" entertainments are forgotten in the actual presence of such marvellous beauty; life becomes a privilege and a blessing after one has seen and thoroughly felt these incomparable types of nature's cunning skill.... Our search for new wonders leading us across the Fire-Hole River, we ascended a gently incrusted slope, and came suddenly upon a large oval aperture with scalloped edges, the diameters of which were eighteen and twenty-five feet, the sides corrugated and covered with a grayish-white silicious deposit, which was distinctly visible at the depth of a hundred feet below the surface. No water could be discovered, but we could distinctly hear it gurgling and boiling at a great distance below. Suddenly it began to rise, boiling and spluttering, and sending out huge masses of steam, causing a general stampede of our company, driving us to some distance from our point of observation. When within about forty feet of the surface it became stationary, and we returned to look down upon it. It was foaming and surging at a terrible rate, occasionally emitting small jets of hot water nearly to the mouth of the orifice.