The Fountains,
Therefore, That We See Mounting To The Sky During An
Eruption, Are Nothing But The Superincumbent Mass Of
Waters In The Pipe Driven Up In Confusion Before The
Steam At The Moment It Obtains Its Liberation.
[Footnote:
Professor Bunsen has lately announced a chemical theory,
which I believe has been received with favour by the
scientific world.
He points to the fact that water, after
being long subjected to heat, loses much of the air
contained in it, has the cohesion of its molecules much
increased, and requires a higher temperature to bring it
to boil; at which moment the production of vapour becomes
so great, and so instantaneous, as to cause explosion.
The bursting of furnace boilers is often attributable to
this cause. Now, the water at the bottom of the well of
the Great Geysir is found to be of constantly increasing
temperature up to the moment of an eruption, when on one
occasion it was as high as 261 degrees. Fahrenheit.
Professor Bunsen's idea is, that on reaching some unknown
point above that temperature, ebullition takes place,
vapour is suddenly generated in enormous quantity, and
an eruption of the superior column of water is the
consequence.]
The accompanying sketch may perhaps help you to understand
my meaning.
[Figure: fig-p074.gif]
The last gulp of water had disappeared down the funnel.
We were standing at the bottom of the now empty basin,
gazing into each other's faces with joyous astonishment,
when suddenly we perceived a horseman come frantically
galloping round the base of the neighbouring hill towards
us.
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