brisk walk will bring us to them. The mud springs, which
are scattered over an area of several hundred acres, present many
strange and interesting features. There are holes in the earth with
bubbling mud at the bottom, cones from the tops of which streams
of muddy water issue, and ponds of mud, in some cases as thick
as molasses, in others thin and watery. There are little jets of
steam, strange odors, and a vista of many mingled colors. Taken
altogether, it is a place quite different from any other that we
have ever seen.

The ground is soft and marshy, and in some places undermined by
the water, so that we have to take great care in walking about.
Some of the smaller springs occupy round depressions, sometimes
three or four feet across, which look as if they had been made
by pressing a large pan down into the clay. The bubbling mud in
the bottom of the pan, as well as the hot water in many of the
springs, makes it easy to imagine that we are standing upon the
top of a great cooking stove in which a hot fire is burning. As
the gas with which the water is impregnated comes up through the
mud, it forms huge bubbles which finally break and settle down,
only to rise again. In this way concentric mud rings, perfect in
form, are made to cover the entire surface of the pool.

Where there is little water, the surface of the mud hardens and
leaves a small opening, through which the bubbling gas throws small
columns of mud at regular intervals. From the large pools, some
of which are forty to fifty feet in diameter, there comes a low
murmuring sound like the boiling of many kettles. The water is
sputtering and bubbling, and in some places it is hot enough to give
off thin clouds of steam. Occasionally we get whiffs of sulphur,
while about the borders of some of the ponds pretty crystals of
this mineral can be found.

More commonly the pools are crusted about with a white deposit
of salt, for they all contain more or less of this substance in
solution. Around a few of the pools the mud is stained with the
red tinge of iron, and red lines mark the paths of the streams
as they run off from the pools toward the still lower portions of
the desert.

[Illustration: FIG. 31.--POT-HOLES]

The built-up cones or volcanoes appear in every stage, from the
little ones a few inches high to the patriarchs, which in some
cases have reached a height of twelve feet. These cones are formed
by the hardening and piling up of mud about the op