appear at the surface until
they have heated the water to their own temperature.

"'When so much vapor has escaped that the expansive force of that which
remains has become less than the pressure of the confining column of
water, tranquility is restored, and this lasts until such a quantity of
vapor is again collected as to produce a fresh eruption. The spouting of
the spring is therefore repeated at intervals, depending on the
capacity of the cavern, the height of the column of water, and the heat
generated below.'" Dr. Peal continues:

"Bishof says that the eruptions of the Geyser and Strockr agree exactly
with this explanation and he accounts for the two distinct classes of
eruption observed in the Geyser as follows:

"'The two distinct classes of eruption in the geyser which we have
already mentioned seem to be attributable to two different cavities. A
small cavity fills quicker, and, therefore, empties itself more
frequently; a larger one fills slower, empties itself seldomer, but with
greater violence.'"

Bunsen's theory is the next considered and is somewhat similar to
Bischof's but with notable differences. After taking temperatures at
different points in the Geyser tube his first conclusions are that:

(1) The temperature in the geyser tube increases as we descend.

(2) At no point does the water in the tube attain the temperature of
ebullition which it should have under the pressure to which it is
subjected, but the temperature depends on the time that has elapsed
since the last eruption. As a great eruption comes near it approaches
the boiling point.

(3) At the depth of about forty-five feet the difference between the
temperature of the water and the calculated boiling point for that
pressure is the least.

The main point of his theory appears to be that an eruption takes place
when the water in the tube reaches the boiling point, and to account for
it, "He supposes that the column in the central tube communicates by a
long and sinuous channel with some space, be it what it may, which is
subjected to the action of the direct source of subterranean heat. The
temperature gets raised above the boiling point, due to the pressure,
and a sudden generation of steam is the result. This steam rises in the
column of water, which, being cooler, causes it to condense. Gradually
the heat of the water is raised until the water of the channel must
boil, and the steam therefore cannot condense, but must accumulate