greater pressure more heat is required to
make steam. The water never leaps and bubbles in an engine boiler.
The awful pressure compels it to be quiet. A cubic inch of water will
make a cubic foot--one thousand seven hundred and twenty-eight times as
much--of steam under the pressure of one atmosphere. But under the
pressure of a column of water one thousand feet high, giving a pressure
of four hundred and thirty-two pounds to the square inch at the bottom,
water becomes steam, if at all, only by great heat. Every engineer
knows that the pressure exerted by steam increases by great geometrical
ratios as the heat increases by small arithmetical ratios. Steam made
by two hundred and twelve degrees exerts a pressure, as we have said,
of fifteen pounds.

To simply double the two hundred and twelve degrees of heat increases
the steam pressure twenty-three times.

Now suppose the subterranean tube or lake of Old Faithful to be freshly
filled with its million gallons of water. Sufficient heat makes steam
under any pressure. It rises up the tube and is condensed to water
again by the colder water above. Hence no commotion. But the whole
volume of water grows hotter for an hour. When it is too hot to absorb
the steam, and the tube is too narrow to let the amount made bubble up
through the water, it lifts the whole mass with a sudden jerk. The
instant the pressure of the water is taken off in any degree, the water
below, that was kept water by the pressure, breaks into steam most
voluminously, and the measureless power floods the earth and sky with
water and steam.

It is also known that superheated steam suddenly takes on such great
power that no boiler can hold it. Once let the water in a boiler get
very low and no boiler can hold the force of the resultant superheated
steam. The same heat that, applied to water, gives perfect safety,
applied to steam gives utter destruction. Hence the amazing force of
the vast jets of the geyser that follow the first spurts.

As soon as the steam is blown off the subterranean waterworks fill the
tube and the process is repeated.

This modus operandi was first proposed as a theory by Bunsen in 1846,
and later was demonstrated by the artificial geyser of Professor J. H.
J. Muller, of Freiburg.

[Illustration: Pulpit Terrace and Bunsen Peak.]

MOUNDS OF MINERAL DEPOSITS

I have the extremely difficult task of representing emotions by
words--glories of color and form seen