st beyond which is another brimstone basin
containing forty or fifty boiling sulphur and mud springs, and any
number of small steam jets. A small creek runs through the basin, and
the slopes of the mountains on either side to the height of several
hundred feet showed unmistakable signs of volcanic action beneath the
crust over which we were traveling. A considerable portion of the slope
of the mountain was covered with a hollow incrustation of sulphur and
lime, or silica, from which issued in many places hot steam, and we
found many small craters from six to twelve inches in diameter, from
which issued the sound of the boiling sulphur or mud, and in many
instances we could see the mud or sulphur water. There are many other
springs of water slightly impregnated with sulphur, in which the water
was too hot for us to bear the hand more than two or three seconds, and
which overflowed the green spaces between the incrustations, completely
saturating the ground, and over which in many places the grass had
grown, forming a turf compact and solid enough to bear the weight of a
man ordinarily; but when it once gave way the underlying deposit was so
thin that it afforded no support. While crossing, heedless of General
Washburn's warning, one of these green places, my horse broke through
and sank to his body as if in a bed of quicksand. I was off his back in
an instant and succeeded in extricating the struggling animal, the turf
being strong enough to bear his body alone, without the addition of the
weight of a man. The fore legs of my horse, however, had gone through
the turf into the hot, thin mud beneath. General Washburn, who was a few
yards behind me on an incrusted mound of lime and sulphur (which bore us
in all cases), and who had just before called to me to keep off the
grassy place, as there was danger beneath it, inquired of me if the
deposit beneath the turf was hot. Without making examination I answered
that I thought it might be warm. Shortly afterwards the turf again gave
way, and my horse plunged more violently than before, throwing me over
his head, and, as I fell, my right arm was thrust violently through the
treacherous surface into the scalding morass, and it was with difficulty
that I rescued my poor horse, and I found it necessary to instantly
remove my glove to avoid blistering my hand. The frenzied floundering of
my horse had in the first instance suggested to General Washburn the
idea that the under stratum w