On the opposite side of the river, along a little branch that flows in from the west, is a considerable group of geysers and boiling springs. Near the base of the mountains is a first-class boiling spring with a curious fungus-like rim. It is always in violent agitation, sending forth great columns of steam. It flows from beneath a hill, and is surrounded with springs whose silicious deposits take the form of the toad-stool fungus. Some of this group may be called spasmodic springs. One, with a most beautifully scalloped rim, fifteen by twenty feet in diameter, is always boiling, and occasionally explodes with great violence, shooting its water several feet into the air.
Along the eastern side of this Lower Geyser Basin are several extensive areas abounding in mud-springs, boiling springs and geysers, whose infinitely varied characteristics can have no more than the briefest notice. Beginning at the north, the first that commands attention is that whose central object of interest is the Thud Geyser, so called from the peculiar noise it makes as the water rises and recedes. It is situated on the slope of a small hill, is about twenty feet in diameter, and has a crater five feet wide and five high, composed of geyserite of a greyish color, full of deep pockets containing balls of the same material, about the size of walnuts, each one covered with little rosette-like formations. The column of water thrown out by this geyser during its eruptions is very wide, and reaches the height of fifty feet. Near it was obtained some pieces of wood, coated with geyserite of a delicate pink tinge: the silica had thoroughly penetrated the woody fibre. There were found, also, pine-cones coated in the same manner, forming beautiful specimens. A few yards back of the geyser are three large mud-springs, in one of which the mud is red, in another white, and in the third pink--the jets of steam causing the mud to assume the form of small conical points throughout the basins. They are situated in a bed of clay, the red color being due to iron. Below these latter are some chalybeate springs whose bright-red iron deposit have spread over a considerable area, in glaring contrast with the white color of the silicious deposits of their neighbors.