For about three hundred yards this tunnel is straight; by looking back the opening can be seen growing smaller and smaller and more distant. At length a great dome-shaped chamber is reached, from which branch out other caves in various directions. Here the dim light of candles, the washing of the water on the rocks, the thunderous booming of the surge in unknown passages far away in the bowels of the mountain, where, every sound being greatly magnified and echoed backwards and forwards, all these produce most weird and awe-inspiring sensations. The mystery and the sense of remoteness from the world, the uncanny feeling that a thousand feet of solid rock lies between one and the sunshine, also add to the effect. But when besides these things, we had been listening to dreadful tales from our boatmen, of mermaids, of sea pigs light green in colour with pink spots and human heads, that at night would come 'wondering' round the boat, and finally of a 'great big beast, a serpent,' as large as the steeple of a church, which was supposed not only to feed on human beings when opportunity offered, but what was worse, was said to inhabit the inner recesses of the very cave in which we were, it is unnecessary to say how easy it was to be frightened at anything. The only unblocked waterway where a boat could pass on out of this domed hall was to the right, and up this we were preparing to go in search of seal, when some exceptionally large waves, tortured in some narrow passages, sent a terrific boom with multitudinous echoes reverberating through the caverns; at the same time a most curious phenomenon, half sound, half vibration of the air occurred. It seemed as though the whole body of the air in the cave pulsated, producing a swishing sound with periods of about one second, which gradually became fainter and fainter till it died away. Probably the cave had been converted into a gigantic organ pipe, and the note was one so low down in the scale that the vibrations were about one per second. Unfortunately I suggested that it was the 'great big beast, the serpent,' and that finished the expedition. Our boatmen were at once terrified, shouting to each other, pushing and half rowing the boat in a frenzy of fear. Amidst the bellowing noises of the various caverns leading out of the central hall, and the angry hisses of 'the beast, the serpent,' we departed most hurriedly for the outer air.