took the lowest calculation. My method
was, to compare the height of the water with
the diameter of the basin, which I knew to
be fifty-one feet, and this jet was full twice
that length. The width of the stream is not
equally easily determined by the eye, on account
of the steam and spray that envelops
it: in most instances, not more, probably,
than eighteen or twenty feet of the surface
of the water is cast into the air; but it
occasionally happens, as was the case now,
that the whole mass, nearly to the edge of
the basin, is at once heaved up: all, however,
is not spouted to an equal height; for the
central part rises the highest, but, having
gained some elevation, the spray divides, and
darts out little jets on every side, that fall
some way over the margin of the basin. After
this last discharge, the water subsided about
fifteen feet in the pipe, and so remained some
time; but in two hours the funnel was again
filled to within two feet of the edge. As often
as I tried the heat of the water in the pipe,
I always found it to be 212°; but, when
the basin also was full, on immersing the
thermometer as far from the margin as I
could reach with my arm, I never saw the
quicksilver rise above 180°; although the
water in the centre was boiling at the same
time. It seems probable that the height to
which the Geyser throws its waters may have
increased somewhat in the course of a few
years; as, when Sir Joseph Banks visited
Iceland in 17 7 the greatest elevation to
which the column ascended, was ascertained
to be ninety two feet; while in the year
1789, its height was taken by a quadrant, by
Sir John Stanley, and found to be near one
hundred feet, and this day, if I am not mistaken,
it was still greater. Povelsen and
Olafsen were in all probability deceived,
when they imagined they saw the loftiest jets
reach to the elevation of sixty toises, or three
hundred and sixty feet. Previously to the
last eruption, Jacob and myself amused ourselves
with throwing into the pipe a number
of large pieces of rock and tufts of grass,
with masses of earth about the roots, and we
had the satisfaction to find them all cast out
at the discharge, when many of them fell
ten or fifteen feet beyond the margin. Some
rose considerably higher than the jets which
forced them up: others fell down into the
basin, and were with the following eruption