indication that both these caves have been subject to the action of
enormous volumes of water, there is equally positive evidence that
neither was ever the scene of a flowing cave-river. The lowest levels in
both show the narrowest fissures and the heaviest deposits of crystal,
by which we infer that the water was held in confinement here, while all
the higher passages or channels bear witness to the water's flow. But
many of these channels in Crystal Cave, or indeed we might say, most of
them, present an unmistakable record of the gauge of the water stage at
different periods. During the earlier time, when the volume of water and
consequent pressure were greatest, frictional motion must have been
limited to the main channel connecting with the vent, and the high gauge
of water maintained a fairly uniform degree of heat near its surface. In
consequence of these conditions geyser action, probably, was constant,
and chemical activity was such that great chambers were formed and then
decorated, as already described, with wonderful masses of crystal. As
the water gauge receded to lower levels the higher chambers became
storage basins for water and steam forced up by the pressure from below,
and the time required for these to fill and accumulate sufficient
pressure to continue the ejectment, formed the periods between eruptions
after the geyser became intermittent. It was during this stage that the
sharp crystals in many of the channels, now called passages, were worn
down to smooth surfaces; and later, when water occupied only the lowest
level, and the great geyser had become reduced to merely a steam vent,
the channels immediately connecting with that level were in their turn
subjected to the same smoothing process, and then all action ceased.

As no two of the glorious geysers of the Yellowstone Park are alike,
neither do the two great caves of the Hills indicate that they should be
so. The vent-tubing of each is quite unlike that of the other in all the
essential governing points of length, size, shape, angle of inclination
and power-conserving bends. And the differences extend in an almost
equally marked degree throughout the vast and complicated succession of
storage chambers and their connecting channels. The small vent of Wind
Cave shows that the ejected jet was far from being equal to that of the
Crystal Cave in volume; but the nearly perpendicular long arm of its
tube shows also that its jet attained a much greater