Downward--the water seething and boiling around the vessel, threatening each moment to beat in the glass of the turret; still downward--the _Seal_ whirling like a straw in the grip of the maddened waters, and the occupants of her turret clinging for dear life to the walls. The deck of the vessel sloped like the roof of a house as she surged downward in the glissade of waters. Behind her an inky wall curled and foamed, urging her into the depths. Then suddenly she righted for a moment, and Haverly, gazing out anxiously over the waste of waters from his post at the wheel, caught a glimpse of a fearful black chasm, which yawned where once the bed of the lake had been, and into this the waters were plunging in a mighty cataract. “My God!” cried the American hoarsely, and even as the prayer left his lips, the vessel lurched, heeled over, and was borne swiftly downward into the depths of the abyss. CHAPTER V. OVER THE CATARACT’S BRINK. TWICE the _Seal_ turned turtle in the course of that terrible dive, dashing her crew with stunning force against the turret walls. In vain they strove to regain their balance. Helpless as logs they were hurled to and fro, until, battered beyond all human endurance, they one and all sank into insensibility. And still the submarine plunged downward, still she lurched and wallowed in the rioting waters. Suddenly she was brought up with a fearful shock that snapped off both propellers like rotten sticks. A veritable avalanche of water thundered down upon her, battering her hull so that the steel plates groaned beneath the enormous strain. Each instant it seemed as though the stout glass of the turret must be beaten in; yet it held bravely, and at length the downpour ceased, and the _Seal_ shot forward like an arrow. Two hours went by, and then Haverly recovered his senses. Staggering to his feet, he steadied himself against the wheel, and gazed outside. The rays of the great searchlight gleamed white and dazzling on the walls and roof of a rocky tunnel, through which the _Seal_ was racing at headlong speed, urged on by the fearful force of the torrent, on whose foaming bosom she was borne. With an effort--so enfeebled was he by his terrible experience--Silas moved to the door. To his great joy it opened easily, and he flung it wide, admitting a flood of life-giving air. “Thank Heaven!” he murmured fervently, damping his parched and blackened lips, while he drew in deep draughts of pure, cool air; “another hour and we’d all have passed in our checks.” Turning, he found his friends already stirring, their recovery hastened by the beneficent influence of the refreshing atmosphere. Crowding to the door, they stood for some moments filling their exhausted lungs. “Whatever have we struck?” Seymour asked at length, gazing in amazement at the dripping, glistening walls of the passage.