from the spray of its waters. The diameter of
this basin, in one direction, is fifty-six feet, and forty-six in
another. (See fig. 94.) In the centre is a pipe seventy-eight feet in
perpendicular depth, and from eight to ten feet in diameter, but
gradually widening, as it rises into the basin. The inside of the basin
is whitish, consisting of a siliceous crust, and perfectly smooth, as
are likewise two small channels on the sides of the mound, down which
the water escapes when the bowl is filled to the margin. The circular
basin is sometimes empty, as represented in the following sketch; but is
usually filled with beautifully transparent water in a state of
ebullition. During the rise of the boiling water in the pipe, especially
when the ebullition is most violent, and when the water is thrown up in
jets, subterranean noises are heard, like the distant firing of cannon,
and the earth is slightly shaken. The sound then increases and the
motion becomes more violent, till at length a column of water is thrown
up, with loud explosions, to the height of one or two hundred feet.
After playing for a time like an artificial fountain, and giving off
great clouds of vapor, the pipe or tube is emptied; and a column of
steam, rushing up with amazing force and a thundering noise, terminates
the eruption.

[Illustration: Fig. 94.

View of the Crater of the Great Geyser in Iceland.[775]]

If stones are thrown into the crater, they are instantly ejected; and
such is the explosive force, that very hard rocks are sometimes shivered
by it into small pieces. Henderson found that by throwing a great
quantity of large stones into the pipe of Strockr, one of the Geysers,
he could bring on an eruption in a few minutes.[776] The fragments of
stone, as well as the boiling water, were thrown in that case to a much
greater height than usual. After the water had been ejected, a column of
steam continued to rush up with a deafening roar for nearly an hour; but
the Geyser, as if exhausted by this effort, did not send out a fresh
eruption when its usual interval of rest had elapsed. The account given
by Sir George Mackenzie of a Geyser which he saw in eruption in 1810
(see fig. 95), agrees perfectly with the above description by Henderson.
The steam and water rose for half an hour to the height of 70 feet, and
the white column remained perpendicular notwithstanding a brisk gale of
wind which was blowing against it. Stones thrown into the pipe were