The floor of the pot and the cave was strewn with masses of limestone rounded by the action of the streams; and the water-channels were smoothed and grooved and polished, in a most extraordinary way, by the silt and stones carried along by the current. Some of the layers of limestone were jet black, and others were of a light fawn-colour, and as the strata were nearly horizontal, the alternation of colours gave a peculiarly striking effect to the walls. Beneath each waterfall was a pool more or less deep, and here and there in the bed of the stream were holes, drilled in the rock by stones whirled round by the force of the water. High up, out of the present reach of the water, were old channels, which had evidently been watercourses before the pot and cave had been cut down to their present level. In the sides of the pot there are two vertical grooves reaching very nearly from the top to the bottom, which are unmistakeably the work of ancient waterfalls. There was no stalactite, but everywhere the water was wearing away the rock and enlarging the cave. We found our way back without any difficulty, a small passage on the right-hand side enabling us to avoid the very unpleasant task of scrambling up two of the waterfalls. We arrived finally at the top, after about five hours’ work in the cave, wet to the skin. We had very little trouble in making this descent, because of the completeness of Mr. Birkbeck’s preparations; but we could fully realize what a dangerous feat the first explorers performed when they ventured into an unknown chasm, comparatively unprepared. The very name “Helln Pot,” = Ællan Pot, or Mouth of Hell, testifies to the awe with which the Angles looked down into its recesses.[31] Such is the interior of one of those great natural laboratories in which water is wearing away the solid rock, either hollowing it into caves or cutting it into ravines. At the bottom of Helln Pot it was impossible not to realize, that the enormous chasm had been formed by the same action as that by which it was being deepened before our eyes. It was merely a portion of the vast cave into which it led, which had been deprived of its roof, and opened out to the light of heaven. The bridge was but a fragment of the roof which happened to fall upon the two ledges. The rounded masses of rock at the bottom are fragments that have fallen probably within comparatively modern times. The absence of stalactites and of stalagmites proves that the destructive action is rapidly going on. The water-course at the bottom contained pebbles and boulders of limestone, and gritstone rounded by friction against one another and the rocky floor. The gritstone has probably been derived from the wreck of the boulder clay on the surface above the Helln Pot, and ultimately torn from the millstone grit of the higher hills in the district. _Caves and Pots at Weathercote._ [Illustration: FIG. 5.--Waterfall in Pot-hole at Weathercote.]