Now suppose this tube to
be filled with water from surface or subterranean sources. Heat
converts water, under the pressure of one atmosphere, or fifteen pounds
to the square inch, into steam at a temperature of two hundred and
twelve degrees. But under 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.
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