Two hundred yards below the Giant is the Grotto so named from the curious irregularity of its inclosing walls. It has an exceedingly intricate formation, with fantastic arches, pillars, and turreted sides, and discharges several times a day. Several of the first explorers crawled through the sinuous apertures when all was quiet. It seemed as harmless as curious then, but their opinion was changed slightly when they saw it an hour after throwing a column of water six feet in diameter to the height of sixty feet. Near it are several vents in which the water boils constantly to the height of six feet, large streams running down the banks into the river.
Around the point of a hill a few hundred yards south of the Grotto, and partially concealed by a grove of pines, is a white cone twenty-five feet high and a hundred feet in diameter at the base. It has evidently been a geyser of considerable importance, but it now merely sends forth puffs of steam from a small orifice at the top. Near it is a quiet hot-spring with a most elegantly scalloped rim. Back of this Pyramid is the Punch Bowl, and still further south, the Black Sand Geyser, neither of which has been specially described.
Returning to the river and crossing we find at the water's edge, nearly opposite the Grotto, the Riverside Geyser, and a short distance below, on the same side, is the Fan. The latter geyser has a double orifice, which discharges five radiating jets to the height of sixty feet, the falling drops and spray giving the appearance of a feather fan. The effect is very beautiful. Its eruptions are frequent, lasting usually from ten to thirty minutes. A vent connected with it, about forty feet distant, expels dense masses of vapor fifty or sixty feet high, accompanied by loud, sharp reports, during the time the geyser is in action. Lieutenant Doane describes the curious action of these vents as follows:
"First the steam would rush from the upper crater, roaring violently, then this would suddenly cease, to be followed by a fan-like jet of water rising from the lower crater to the height of over forty feet, playing for perhaps two minutes; then this would suddenly stop flowing, and the steam would rush forth again for a time. Occasionally the small crater threw a transverse stream, alternating with the others; and thus they played on for hours, after which all would subside to a gentle bubbling."
FAN GEYSER.
Along both banks of the river are small craters built up in every conceivable shape. Several streams pour out cascades from round holes in the rocky bank of the river, and all around are little geysers playing at intervals from six to forty feet.
A plateau opposite the Fan contains fifteen hot springs of various characteristics; some are of a deep blue color and have fantastic caverns distinctly visible below the surface of the water. The openings at the surface are often beautifully edged with delicately wrought rock fringes. One variety deposits a red or brown leathery substance, partially adhering to the sides and bottom of the cavern and waving to and fro like water plants. In size these springs vary from five to forty feet in diameter.