INSIDE THE OGO, NEAR ABERGELE.
Photo by E. A. Baker.
The line of the fissure creating the upward chasms inside the cave can be traced in the external configuration of the cliff; in sundry vertical openings in the face, and in the clean-cut walls, where sheer masses have fallen away, broken at the joints. Similar joints and fissures played a part in the formation of a lower tier of caves, which we explored next. The first was only a yard or two wide, but very lofty, and its floor was composed of a level bed of sand and clay. This gradually rose as we walked into the darkness, until the cave ended more abruptly even than the last. We noticed pebbles of Bunter sandstone in the floor, and the next cave produced many more examples of the same stone, which must have been brought from a long distance, the nearest strata corresponding to it being in Wirral. At the back of this next cave a bank of cave earth and boulder clay was piled right up to the roof, so steeply that it was not too easy a climb to the summit. Arrived there, we found no possible egress; but a horizontal tunnel, a sort of squint or hagioscope probably more than forty feet long, gave us a peep through the rocky cliff out to the sunlight. We set out forthwith to discover the outside orifice of this curious hole, and found it came out on a ledge in the face of the cliff, hard by an open platform which had a very queer look about it. On examination this proved to be the floor of an old cave that had been destroyed by the quarrymen. Half-embedded in thick clay were a number of stalagmite pedestals, and a floor of stalagmite underneath several feet in depth, surmounting a thick bed of boulder clay stuck full of Bunter pebbles. It was obvious that the quarrymen, coming across this mass of useless material, had not troubled to attack the solid layer of stalagmite above it. The remains of stalactites and stalagmite curtains still adhered to the neighbouring cliff.
The spot is well worth visiting, if only to see this remarkable illustration of several consecutive chapters in the history of a cavern. The destructive work of the Limestone quarry, having been checked at this particular point, exposes the whole thing as in a diagram; and the actual evidences are there just as they were produced by the forces acting in successive epochs—the mouth of the original cave, formed perhaps in pre-Triassic times; the masses of drift thrust in by the glaciers; and the new cave floor, with its growth of stalagmites. Since the caves lie at a height of several hundred feet above sea-level, it is fairly certain that the moving glaciers exerted an upward as well as a horizontal force, shoving the plastic masses of clay and débris into the ascending passages, and caulking up, no doubt, a good many tributary galleries that are now unknown. The caves look north, and the material pushed into them must have come from seaward; there is, furthermore, no rock in the adjoining districts that could have yielded this kind of pebbles: so that it appears the stream of glaciers which flowed across from Lancashire and Cheshire, impinging against the contrary flow of ice from Snowdonia, must be held responsible for the presence of these dense deposits. All along the meadow-lands between the Limestone hills and the sea a series of risings or big springs are noticeable from the railway, forming large pools. These are the outlets of the drainage that has been absorbed by the Limestone strata, through which the water has found its way until, meeting with an impermeable layer of rock, or reaching the plane of saturation at sea-level, it has been forced to the surface.
