When the fountain is busy throwing out its volumes of water, the appearance is very peculiar.  Little notice is given of an eruption, which takes place suddenly, although at stated intervals.  All at once the watcher is rewarded for his patience by having the stillness changed into activity of the most boisterous character.  The water is hurled upwards in a mass of frothing, boiling and foaming crystals.  The actual height varies, but frequently goes as far as thirty feet.  In a moment the wall of water becomes compact, oblong and irregular.  Crystal effects are produced, varying according to the time of day and the amount of light, but always delightful and peculiar.

Close at hand are the Mammoth Paint Pots, in the center of the Firehole Geyser.  We can explain the appearance of the Paint Pot or Mud Bath much more easily than we can account for the phenomenon.  It is well named, because it resembles a succession of paint pots of enormous size more than anything else that the imagination can liken it to.  The basin measures forty by sixty feet, with a mud boundary three or four feet high on three sides of it.  The contents of the basin have kept scientists wondering for years.  The substance is white, looking very much like ordinary paint, but, unlike paint, it is constantly in motion, and the agitation is so persistent that an idea is given that the Paint Pot’s basin is the bed of a crater.  The continual bubbling and vibration is very interesting in its effects, and the noise it makes is quite peculiar, not unlike a subdued hiss or a badly executed stage-whisper.  Mixed among the white substance is a quantity of silicious clay of all sorts and conditions of color.  This produces a variation in the appearance, but is merely in addition to what is otherwise marvelous in the extreme.  Pearl gray, with terra cotta, red and green tints is the basic color of this boiling, seething mass, which seems to be continually at unrest and in a course of worry.

The Excelsior Geyser is the most conspicuous feature of the Midway Basin, a collection of hot springs and pools.  They are situated in the Midway Basin, and were originally called Cliff Caldron.  Excelsior Geyser is in a continual state of anarchy, without law, government or regulation.  It does just as it likes and when it likes.  It seldom performs when wanted to, but when it does break out into a condition of fermentation, the effect is very magnificent.  As one writer puts it, the beauties and exhibitions of this geyser are as far superior to those of all the others as the light of the sun seems to that of the moon.