oo much
to be cooled at once, the deposit may still be made fifty or one
hundred feet from the point of issue. If the overflow is sufficient,
it may be building up every inch of a vast cone at once, every foot
being wet.

[Illustration: The Punch Bowl, Yellowstone Geysers.]

Many minerals are held in solution and are deposited at various stages
of evaporation. Let us suppose the lake to have the bottom sloping
toward the abysmal center; the different minerals will be assorted as
if with a sieve. At the Sunlight Basin the edge is as flaming red as
one ever sees in the sunlit sky. And every color ever seen in a sunset
flames almost as brilliantly in the varying depths. Suppose a low cone
to be flooded only occasionally, as in the case of the Old Faithful
geyser. The cooled water falling from the upper air builds up, under
the terrible drench of the cataract, walls three or four inches high,
making pools of every conceivable shape, a few inches deep, in which
are the most exquisite and varied colors ever seen by mortal eye. You
walk about on these dividing walls and gaze into the beaded and
impearled pools of a hundred shades of different colors, never equaled
except by that perpetual glory of the sunset.

Consider the case of a pool that does not overflow. Just as lakes that
have no outlet must grow more and more salt till some have become solid
salt beds, so must this pool, tossing its hot waves two or three feet
high, evaporate its water and deposit its solids. Where? First,
against the cooler sides of the rock under the water, tending to reduce
the opening to a mere throat. Second, each wavelet tossed in air is
cooled, and deposits on the edge, solid as quartz, a crust that
overhangs the pool and tends to close it over as with hot ice. It may
build thus a mound fifteen feet high with an open throat in the middle.
Thus the pool has constructed an intermittent geyser. If the water
supply continues, it also destroys itself. The throat closes up by its
own deposits. It is a case of geyseral membranous croup.

I exceedingly longed to try vivisection on a geyser, or at least take
one of half a hundred, drain it off, and make a post-mortem
examination. On my very last day I found opportunity. I found a dead
geyser, though not by any means yet cold. It was still so hot that
people had given it an infernal name. I squeezed myself down through
its hot throat, which seemed a veritable open sepulcher, and fo