ratures in the side conduit,
I have little doubt he would soon have reached a point where the
temperature would not only be at the boiling point for that depth but
even exceed it. In the Yellowstone Park we obtained a number of surface
temperatures which were above the boiling point. In the Great Geyser of
Iceland, the mass of water in the tube prevents this condition at the
surface, and when it takes place opposite the aperture an eruption is
caused. In the main, however, I am inclined to accept Bunsen's theory,
especially as it seems to me to require subterranean cavities in which
the water must be heated. Whether these are caverns, enlargements of
tubes, or sinus channels, appears to me to be of no consequence, except
as the interval or period of the geyser might be affected by the form of
the reservoir holding the water."

Dr. Peal has reached conclusions which present an imaginary picture of
the interior structure of the great geysers of the Park, that bears a
striking resemblance to what the two caves of the Black Hills prove to
be the true conditions; although it is evident he had in mind caverns of
no such vast extent, nor of so complicated a system of cavities and
tubes. He overlooked an important feature, however, in not accepting
Professor Comstock's idea of the tube having a double curve. The double
curve is, or was, conspicuous in both the caves. Unfortunately, its
perfection in Wind Cave was necessarily partially sacrificed to make the
passage traversable for visitors; but in describing the enormous labor
of opening up the cave, Mr. McDonald showed how an arching "crawl" had
been worked down by blasting, and the depression beyond filled to raise
it to the desired level for securing the present easy passage at the
bottom of the main tube, which is the entrance passage. This double
curve in the tube is simply the rough original of the S trap of sanitary
plumbing. In both caves it is somewhat irregular and deformed, but the
familiar "trap" is easily recognized. The destruction of one of the
Yellowstone geysers was, no doubt, due to the breaking of the S. One of
the many reasons for establishing military control over the Park is said
to have been the disastrous results following the introduction of a
large quantity of soap into the geyser to cause a premature eruption.
The impatience of the party was rewarded by an eruption accompanied by
explosions that shook the earth for a great distance, and the geyser has