This last cave, which not the boldest fisherman in Kilcash or the next village to it would face, was called the Whale's Mouth, and ran in under the Black Rock.
The opening of the Whale's Mouth is on the south-west or extreme seaward side of the Black Rock. At full of spring tide the entrance to it is about fifteen feet high and of equal breadth. The difference between high and low water here is about fifteen feet. Hence, at lowest of spring tide, the measurement from the surface of the water to the roof at the entrance would be thirty feet.
At the entrance of the Whale's Mouth the outline of the Black Rock is blunt, abrupt, solid. The base of the Rock is never uncovered by water. The wash of the long roller of the Atlantic is always against its sides. The general formation of the cave is that of a square. It is more like the hideous distended jaws of the crocodile than of the whale; but the reason for calling it the Whale's Mouth does not lie in the immediate entrance, but further on, in the roof of the forbidding cavern.
For years no one had dared to enter that cavern. Along the coast were stories of two boats which had ventured in. Not a plank, oar, or man of the first had ever been seen again. Part of the boat, oars, and crew of the other had been seen for one brief moment, smashed and mangled, and then disappeared for ever. What the fate of the former was no one could tell; what the fate of the latter had been all knew.
As far as could be seen into the cave from the outside, there was nothing dangerous or remarkable-looking about it. It declined slightly in height, but the walls did not seem to come any closer together. There was no rock or obstruction of any kind visible in it. The long, even swells rolled in unbroken; but after each wave passed out of sight there was a deep tumultuous explosion, and a strange, loud sound of rushing and struggling water. There was no weakening or gradual dispersion of the force of the wave. Its power seemed shattered and absorbed at once.
This cave had another mysterious and disquieting faculty. It absorbed and discharged more water than could be accounted for by any other supposition but that inside somewhere it expanded prodigiously. At flood tide the water went in eagerly; at ebb tide it ran out at so quick a rate, many believed a large body of fresh water, or foreign water of some other kind, found a way into it. On flood tide, the fishermen gave it a wide berth, lest by any chance or mischance they might be sucked into it.
Often curious people passing by at flood tide threw overboard articles that would float, and watched them as they were slowly but surely drawn into that gaping vault. There was no doubt they were swallowed by that inky void, but they never were seen by man again. Some of the simpler people believed that there was a whirlpool at the end of the cave, and that if this whirlpool took anything down, it never gave that thing, or sign or token of that thing, back again. People on these shores attach miraculous powers to whirlpools. There are no whirlpools of consequence in the neighbourhood, but terrible stories of them had reached the people, and filled the simple folk with superstitious awe.
In this shunned and mysterious cell the rock-monster had its home. On the sea it was harmless. But no one durst enter its haunt, and yet this was not wholly from fear of the monster, but of the place itself, with its loud explosions, its unaccountable indraught and outflow, and the unreturning dead of the two boats. The monster had its home in the cave; but his sphere of action was on the vast plain of rock above.
O'Hanlon and O'Brien succeeded in crossing the Black Rock without accident, and were drawing near the Hole.
"It was there," said O'Hanlon, pointing--"just there. I saw him as plain as ever eyes saw anything."