The exchange of places was made, and once more they began to progress with the boat, travelling far more swiftly as they glided on close in to the mighty cliff which rose up overhead, dappled with mossy grey and patches of verdure, dotted with yellow and purple blooms. "To go on like this for ever!" thought Leslie as he swung to and fro, his strong muscles making the water foam as he dipped his oar, watching Louise as she steered, and seemed troubled and ready to converse with Pradelle whenever she caught his eye. "Starn all!" shouted Harry suddenly, as about three miles from home they came abreast of a narrow opening close to the surface of the water. The way of the boat was checked, and Harry looked at the hole into which the tide ran and ebbed as the swell rose and fell, now nearly covering the opening, now leaving it three or four feet wide. "Bound to say there are plenty of good specimens in there," he said. "What do you say, Vic, shall we go in?" "Impossible." "Not it. Bound to say that's the opening to quite a large zorn. I've seen the seals go in there often." "Has it ever been explored?" said Leslie, who felt interested in the place. "No; it's nearly always covered. It's only at low tides like this that the opening is bared. If the girls were not here I'd go in." "How?" said Pradelle. "How?--why swim in." "And be shut up by the tide and drowned," said Louise. "Good thing too," said Harry, with the same look of a spoiled boy at Madelaine. "I don't find life go very jolly. Boat wouldn't pass in there." He had risen from his seat and was standing with one foot on the gunwale, the other on the thwart, gazing curiously at the dark orifice some forty yards away, the boat rising and falling as it swayed here and there on the waves, which ran up to the face of the cliff and back, when just as the attention of all was fixed upon the little opening, from which came curious hissing and rushing noises, the boat rose on a good-sized swell, and as it sank was left upon the top of a weedy rock which seemed to rise like the shaggy head of a huge sea-monster beneath the keel. There was a bump, a grinding, grating noise, a shout and a heavy splash, and the boat, after narrowly escaping being capsized, floated once more in deep water; but Harry had lost his balance, gone overboard, and disappeared. Madelaine uttered a cry of horror, and then for a few moments there was a dead silence, during which Louise sat with blanched face, parted lips, and dilated eyes, gazing at the spot where her brother had disappeared. Pradelle held on by the side of the boat, and Leslie sprang up, rapidly stripped off coat and vest, and stood ready to plunge in.