From The First Burst Upwards
To The Moment The Last Jet Retreated Into The Pipe, Was
No More Than A
Space of seven or eight minutes, and at
no moment did the crown of the column reach higher than
sixty
Or seventy feet above the surface of the basin.
Now, early travellers talk of three hundred feet, which
must, of course, be fabulous; but many trustworthy persons
have judged the eruptions at two hundred feet, while
well-authenticated accounts - when the elevation of the
jet has been actually measured - make it to have attained
a height of upwards of one hundred feet.
With regard to the internal machinery by which these
waterworks are set in motion, I will only say that the
most received theory seems to be that which supposes the
existence of a chamber in the heated earth, almost, but
not quite, filled with water, and communicating with the
upper air by means of a pipe, whose lower orifice, instead
of being in the roof, is at the side of the cavern, and
BELOW the surface of the subterranean pond. The water
kept by the surrounding furnaces at boiling point,
generates of course a continuous supply of steam, for
which some vent must be obtained; as it cannot escape by
the funnel, the lower mouth of which is under water, it
squeezes itself up within the arching roof, until at
last, compressed beyond all endurance, it strains against
the rock, and pushing down the intervening waters with
its broad, strong back, forces them below the level of
the funnel, and dispersing part, and driving part before
it, rushes forth in triumph to the upper air.
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