We gained the summit of the reef without much difficulty. Here, as the bos'n had expressed his opinion, a ledge, barely six feet in width, separated us from the open sea, while on either hand, at a distance of less than a hundred yards, a long reef ran at right angles to the main ledge, terminating in jagged points of disrupted coral nearly half a mile from where we stood. By the deep-blue colour of the water it was evident that there was plenty of depth between these two natural groynes, which formed ample protection from the heavy rollers that at every other point along the reef broke with a ceaseless roar. "You've got your revolver with you, I see, sir," said the bos'n. "I'm going to dive off and see what the rock looks like on the seaward side. There may be sharks about and there may not; but keep a bright look-out, and fire at one if it comes for me. Money," he added to the bowman of the gig, "unreeve the painter and sling it ashore, will you." "There, sir," he continued, "I'll take a turn round the rock, and drop the free end of the rope in the water so that I can pull myself up; but keep a bright look-out, if you please." Hastily divesting himself of his sodden garments, and placing them to dry on the hot stones, the bos'n took a magnificent "header," and cleft the water with hardly a splash. Quite two fathoms down he went before he turned and swam towards the rocky wall, keeping below the water at the same depth. Half a minute later he reappeared, and, shaking the water from his hair, he grasped the rope and came up hand over hand. "That's all right, sir. Deep water both sides, and the rock full of holes." "What do you mean?" asked my father, unable to grasp the meaning of the bos'n's words. "Why, sir, the 'Fortuna' can float easily on either side of this little neck of rock." "On one side, I'll grant." "Aye, on both sides, once we make a way through." "Oh, how do you propose to do it'? Remove each piece of rock bit by bit, when the weight of the smallest is two tons at the very least--eh?" "No, sir," replied the bos'n. "Then how are you going to set about it?" "Blast it," said Mr. Wilkins emphatically. Chapter XIX THE CAVE THE bos'n's proposal was hailed with enthusiasm, for, curiously enough, neither my father nor my uncle had given any thought to the blasting powder the use of which is an everyday occurrence in the mining districts of Cornwall. "How much of the stuff have we?" asked my father. "Mr. Herbert had over fifty pounds of it carried ashore before the gale," replied the bos'n. "It's all in air-tight cases, so it won't be damaged by being buried." "It's a wonder the whole lot hadn't exploded during the storm! There's enough rock brought down from the cliff to show that the shock was exceptionally severe, to say nothing of the chance of it being struck by lightning."