A great master-joint or fissure runs across the hill towards the battlefield, and in it lie the caves, or rather the cave, for so far as we could make out they are all parts of one stream-channel. At the top of a cliff that is now being worked for lime is a small orifice, a mere fox's hole, blocked up against Master Reynard or the badgers that often find a home in these small caves. A hundred feet beneath it is a larger opening, which is said to give entrance into several good-sized chambers; but that also has been carefully built up with fragments of Limestone by the quarrymen. We were driven accordingly to seek the outlet of the cave, and this we found by following the smooth, straight escarpment, produced by the fault, in a wood close to the mainroad. A large stream once issued from the cave mouth, but has since become engulfed in some internal swallet, and emerges a few yards lower down, welling out from a funnel of crystal water some 15 feet deep. The cave itself discharges a stream only in flood-time. There, too, we were stopped from penetrating far by the beds of clay that gradually rose to the cave roof; but in this instance the deposits had been made by the stream, and were not the results of glacial action pushing upwards. In fact, this is a cave with quite a modern history, one still in working order, and used as a waterway at the proper times and seasons by the stream that made it. The Tanyrogo Caves, on the other hand, have ceased for untold ages to be actual water-channels, having been deprived long ago by denudation above and behind them of the greater part of their drainage area. And since that remote epoch they have gone through the series of vicissitudes so plainly recorded in their present physiognomy.
[Illustration: A PRE-GLACIAL CAVE, LLANDULAS.
The other day, a Liverpool friend, who has a bungalow in the Ceiriog Valley, close to Offa's Dyke, told me he had found a cave there, which had never been explored, but was reputed to go six miles underground, to the neighbourhood of Oswestry. He invited me to come down and explore it, and I readily agreed, on the condition that he was to seize the opportunity to make his début as a cave explorer. On the side of the valley where the cave lies the hill falls steeply to the Ceiriog, and the densely-wooded cliff of Limestone that bathes its foot in the river is like a bit of Dovedale. Not so the other side of the valley, where different strata crop out, and the hills, with all their trees, rise more gently to the brow overlooking Llangollen.