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.
The lower reaches of the valley of Gardiner's River, and the enclosing hillsides, are strewn with volcanic rock, having the appearance of furnace cinder. The tops of the rounded hills are covered with fragments of basalt and conglomerate, whose great variety of sombre colors add much to the appearance of desolation which characterizes the valley. Here and there are stagnant lakes fifty to a hundred yards in diameter, apparently occupying ancient volcanic vents. Crossing a barren, elevated region two miles in extent, and three or four hundred feet above the river-bed, the trail descends abruptly to a low "bottom" covered with a thick calcareous crust, deposited from hot springs, now for the most part dry. At one point, however, a large stream of hot water, six feet wide and two feet deep, flows swiftly from beneath the crust, its exposed portion clearly revealed by rising steam. The quantity of water flowing from this spring is greater than from any other in this region; its temperature ranges from 126° to 132° Fah. A little further above are three or four other springs near the margin of the river. These have nearly circular basins, six to ten feet in diameter, and a temperature not above 120°. Already these springs have become the resort of invalids, who speak highly of the virtues of the waters. A short distance up the hill are abundant remains of springs, which in time past must have been very active. For nearly a mile the steep hill-side is covered with a thick crust of spring deposits, which, though much decomposed and overgrown with pines and cedars, still bear traces of the wonderful forms displayed in the vicinity of the active springs further up the hill. Ascending the hill, Dr. Hayden's party came suddenly and unexpectedly upon these marvellous deposits, which they agreed in pronouncing one of the finest displays of natural architecture in the world. The snowy whiteness of the deposit, which has the form of a frozen cascade, at once suggested the name of White Mountain Hot Spring. The springs now in active operation cover an area of about one square mile, while the rest of the territory, three or four square miles in extent, is occupied by the remains of springs which have ceased to flow. Small streams flow down the sides of the Snowy Mountain in channels lined with oxide of iron of the most delicate tints of red. Others show exquisite shades of yellow, from a deep, bright sulphur, to a dainty cream-color. Still others are stained with shades of green, all these colors as brilliant as the brightest aniline dyes. The water after rising from the spring basin flows down the sides of the declivity, step by step, from one reservoir to another, at each one of them losing a portion of its heat, until it becomes as cool as spring-water. Within five hundred feet of its source Dr. Hayden's party camped for two days by the side of the little stream formed by the aggregated waters of these hot springs, and found the water most excellent for drinking as well as for cooking purposes. It was perfectly clear and tasteless, and harmless in its effects. During their stay here all the members of the party, as well as the soldiers comprising their escort, enjoyed the luxury of bathing in these most elegantly carved natural bathing-pools; and it was easy to select, from the hundreds of reservoirs, water of any desired temperature. These natural basins vary somewhat in size, but many of them are about four by six feet in diameter, and one to four feet in depth. Their margins are beautifully scalloped, and adorned with a natural beadwork of exquisite beauty.
BATHING-POOLS (DIANA'S BATH.)
The level or terrace upon which the principal active springs are located, is about midway up the sides of the mountain, covered with the sediment. Still farther up are the ruins of what must have been at some period more active springs than any at present known. The sides of the mountain for two or three hundred feet in height, are thickly encrusted with calcareous deposit, originally ornamented with elegant sculpturing, like the bathing pools below; but atmospheric agencies, which act readily on the lime, have obliterated all their delicate beauty.
The largest living spring is near the outer margin of the main terrace. Its dimensions are twenty-five feet by forty, and its water so perfectly transparent that one can look down into the beautiful ultramarine depth to the very bottom of the basin. Its sides are ornamented with coral-like forms of a great variety of shades, from pure white to a bright cream yellow, while the blue sky reflected in the transparent water gives an azure tint to the whole which surpasses all art. From various portions of the rim, water flows out in moderate quantities over the sides of the hill. Whenever it gathers into a channel and flows quite swiftly, basins with sides from two to eight feet high are formed with their ornamental designs proportionately coarse; but when the water flows slowly, myriads of little basins are formed, one below another, with a semblance of irregular system. The water holds in solution a great amount of lime, with some soda, alumina and magnesia, which are slowly deposited as the water flows down the sides of the mountain. Underneath the sides of many of the pools are rows of exquisitely-ornamented stalactites, formed by the dripping of the water over the margins. All these springs have one or more centres of ebullition which is constant, though seldom rising more than four or five inches above the surface. The ebullition is due mainly to the emission of carbonic acid gas. The springs in the centre of the main basin are probably all at the boiling point—194° at this elevation. Being inaccessible, however, it is impossible to determine their actual temperature. The hottest that could be reached was 162° Fah. The terrace immediately above the main basin is bordered by a long rounded ridge with a fissure extending its whole length, its interior lined with beautiful crystals of pure sulphur. Only hot vapors and steam issue from this fissure, though the bubbling and gurgling of water far beneath the surface can be distinctly heard. Back of this ridge are several small springs which throw up geyser-like jets of water intermittently to the height of three feet.
On the west side of this deposit, about one-third of the way up the White Mountain from the river and terrace, where was once the theatre of many active springs, old chimneys or craters are scattered thickly over the surface, and there are several large holes and fissures leading to vast caverns below. The crust gives off a dull hollow sound beneath the tread, and the surface gives indistinct evidence of having been adorned with the beautiful pools or basins already described. At the base of the principal terrace is a large area covered with shallow pools some of them containing water, with all the ornamentations perfect, while others are fast going to decay, and the decomposed sediment is as white as snow. On this sub-terrace is a remarkable cone about 50 feet in height and 20 feet in diameter at the base. Its form has suggested the name of Liberty Cap. It is undoubtedly the remains of an extinct geyser. The water was forced up with considerable power, and probably without intermission, building up its own crater until the pressure beneath was exhausted, and the spring gradually closed itself over at the summit and perished. No water flows from it at the present time. The layers of lime were deposited around the cap like the layers of straw on a thatched roof, or hay on a conical stack. Not far from the Liberty Cap is a smaller cone, called, from its form, the "Bee-hive." These springs are constantly changing their position; some die out, others burst out in new places. On the northwest margin of the main terrace are examples of what have been called oblong mounds. There are several of them in this region, extending in different directions, from fifty to one hundred and fifty yards in length, from six to ten feet high, and from ten to fifteen feet broad at the base. There is in all cases a fissure from one end of the summit to the other, usually from six to ten inches wide, from which steam sometimes issues in considerable quantities, and on walking along the top one can hear the water seething and boiling below like a cauldron. The inner portion of the shell, as far down as can be seen, is lined with a hard, white enamel-like porcelain; in some places beautiful crystals of sulphur have been precipitated from the steam. These mounds have been built up by a kind of oblong fissure-spring in the same way that the cones have been constructed. The water, continually spouting up, deposited sediment around the edges of the fissure until the force was exhausted, and then the calcareous basin was rounded up something like a thatched roof by overlapping layers.
