Mark had beaten about ‘Oval Harbour,’ as he named the place, for half an hour, before he was struck by the circumstance that the even character of its surface appeared to be a little disturbed by a slight undulation which seemed to come from its north-eastern extremity.  Tacking the Bridget, he stood in that direction, and on reaching the place, found that there was a passage through the rock of about a hundred yards in width.  The wind permitting, the boat shot through this passage, and was immediately heaving and setting in the long swells of the open ocean.  At first Mark was startled by the roar of the waves that plunged into the caverns of the rocks, and trembled lest his boat might be hove up against that hard and iron-bound coast, where one toss would shatter his little craft into splinters.  Too steady a seaman, however, to abandon his object unnecessarily, he stood on, and soon found he could weather the rocks under his lee, tacking in time.  After two or three short stretches were made, Mark found himself half a mile to windward of a long line, or coast, of dark rock, that rose from twenty to twenty-five feet above the level of the water, and beyond all question in the open ocean.  He hove-to to sound, and let forty fathoms of line out without reaching bottom.  But everywhere to leeward of him was land, or rock; while everywhere to windward, as well as ahead and astern, it was clear water.  This, then, was the eastern limit of the old shoals, now converted into dry land.  Here the Rancocus had, unknown to her officers, first run into the midst of these shoals, by which she had ever since been environed.

It was not easy to compute the precise distance from the outlet or inlet of Oval Harbour, to the crater.  Mark thought it might be five-and-twenty miles, in a straight line, judging equally by the eye, and the time he had been in running it.  The Summit was not to be seen, however, any more than the masts of the ship; though the distant Peak, and the column of dark smoke, remained in sight, as eternal land-marks.  The young man might have been an hour in the open sea, gradually hauling off the land, in order to keep clear of the coast, when he bethought him of returning.  It required a good deal of nerve to run in towards those rocks, under all the circumstances of the case.  The wind blew fresh, so much indeed as to induce Mark to reef, but there must always be a heavy swell rolling in upon that iron-bound shore.  The shock of such waves expending their whole force on perpendicular rocks may be imagined better than it can be described.  There was an undying roar all along that coast, produced by these incessant collisions of the elements; and occasionally, when a sea entered a cavern, in a way suddenly to expel its air, the sound resembled that which some huge animal might be supposed to utter in its agony, or its anger.  Of course, the spray was flying high, and the entire line of black rocks was white with its particles.