and
acquire a gradually increasing tension. The condensation of the bubbles
possesses a periodic character, and to this is due the uplifting of the
water in what Bunsen calls conical water hills, which are accompanied by
the subterranean explosions."

Prof. Comstock is quoted as thinking "Bunsen's theory has not yet been
proved adequate to explain the more prominent features of geyser
eruptions. Nor does it, in his opinion, account for all the differences
between geysers and hot springs, and he proposes a structural
hypothesis which combines Bischof's and Bunsen's theories."

This hypothesis is illustrated by a figure in which a reservoir partly
filled with water is connected with the surface by a tube having a
double curve, and he explains that the water collecting in the depressed
curve should confine the steam, rising from the reservoir in the other
curve until the pressure is sufficient to cause an eruption. His theory
of action being that the water in the reservoir remains in equilibrium
at a certain level, and the constant heat fills the space above with
vapor, which heats the water held in the downward bend of the tube, and
that also evolves vapor which fills the balance of the tube to the vent.
When the combined pressure of this vapor and water are overcome by the
expansion of vapor accumulated above the reservoir, they are forced out,
and followed by a portion of the water of the reservoir. This theory is
in the report of Captain Jones on Northwestern Wyoming.

The last theory cited by Dr. Peal is that of S. Baring-Gould, "Who
visited the Iceland geysers in 1863, and thinks that a bent tube is
sufficient to explain the action of the Great Geyser. He took an iron
tube and bent it in an angle of 110 deg., keeping one arm half the length
of the other. He filled the tube with water and placed the short arm in
the fire. For a moment the surface of the liquid remained quiet, and then
the pipe began to quiver; a slight overflow took place, without any sign
of ebullition, and then suddenly, with a throb, the whole column was
forced high into the air. With a tube, the long arm of which measured
two feet and the bore of which was three-eighths of an inch, he sent a
jet to the height of eighteen feet. Steam is generated in the short arm
and presses down the water, causing an overflow until the steam bubble
turns the angle, when it forces out the column in the long arm with
incredible violence."

Dr. Peal now goes on t