The cave mouth is about 20 feet above the river, in a cliff facing due north, in which the Limestone is tilted at an angle of 45 degrees. It is recessed within a lofty arch, but the entrance itself is low, compelling us to creep for the first few yards. After two or three bends, the roof as well as the floor rises, and the passage opens into a chamber whose floor is heaped up to a height of 10 feet with fallen débris, thickly plastered with mud. At first the cave runs due south, but the main axis of this chamber, which is lofty and measures about 20 feet by 20, runs east-south-east. The roof rises about 20 feet higher than the central heap of débris. Water drips occasionally, but there are no stalactites. At the far end the passage turns south-east, and, though lofty, is narrow, the walls being parallel, and tilted at an angle of 20 degrees from the perpendicular. Then a second chamber widens out, 50 feet long by 6 feet broad, as muddy as the former. Rising 10 feet, the passage continues to the east-south-east, but the walls converge for a time, forcing us to crawl, extended on our sides. Then it opens out again, and we climb over more heaps of débris littering the floor, and all bedaubed with thick, tenacious clay. Now the passage becomes loftier but narrower, and progress has to be made by keeping near the roof, the walls sloping at an angle of 30 degrees from the vertical, opening at one point into a small chamber with a false floor of jammed rocks, then immediately closing again, and so continuing for a distance of 60 feet. The narrowness is so great that one goes ahead only by dint of a continuous struggle against friction. Up to this, my friend had kept close at my heels, followed by his man. But here the only way visible was down a still narrower rift bending off to the left, and the latter found his own diameter greater than that of the cave. We left him, and pushed obstinately forward, though we had not seen a sign of any person's former presence for a long distance. Nearer the cave mouth matches and candle-grease and the marks of crawling had been plentiful, local adventurers having got in nearly 100 feet. [Illustration: ON THE CEIRIOG. _Photo by E. A. Baker._] [Illustration: UPPER CEIRIOG CAVE. _Photo by E. A. Baker._]