Not a word passed between the occupants of her wheelhouse. Each was anxiously looking for an opening, even the cool-blooded Yankee being somewhat concerned at this deadlock. As the moments went by without their hopes being realised, a fit of gloomy depression swept over them all, which was lifted at length, as a sharp cry broke from Seymour. “Look!” The submarine had crept round a great out-jutting spur of the ice-cliffs, and before her, in the face of the glittering wall, loomed a monstrous archway, full one hundred feet in width and almost as much in height. Before this enormous cavern the millionaire brought the _Seal_ to, with her brow pointing directly into the darkness, which even the rays of the searchlight failed to dispel for more than a few yards distant. “I reckon we might do worse than try this,” he suggested. “Take her in,” Mervyn said eagerly; “there is a chance. We can but return, should it prove to be a _cul-de-sac.”_ Forthwith the submarine passed cautiously through the archway into the great domed chamber which opened beyond. Through this she crept, with searchlight flashing on the alabaster walls, till a second archway loomed before her, smaller than the first, yet wide enough to give her passage. Her pace within this narrow tunnel was scarcely a crawl, but no faster dared Haverly drive her, lest, through the sudden narrowing of the passage, she should collide with the ice. Two hours dragged by, and still the eternal ice gleamed around them in dazzling monotony, and they grew sick of gazing upon its never-ending sameness. Mervyn alone knew no weariness. Close to the glass he stood, his nervous hands clenching and unclenching as he gazed ahead. Suddenly a glad cry pealed from his lips. “At last!” The ice tunnel had ended; the _Seal_ had passed out into open water. “Raise her,” roared the American down the tube. “I guess we’ve struck the Polar Sea!” The scientist could scarcely control his eagerness as the submarine slowly rose. Back and forth he paced, as the tinge of the water without faded from deep green to grey. Then the dim light gave way to a flood of brilliant sunshine, and Garth switched off the searchlight, as the _Seal_ emerged into the full glory of the Northern sun. For here no leaden grey sky overhung the scene, but a pure blue vault of matchless brilliance, its beauty unmarred by a single cloud. As, in response to Haverly’s signal, the engines stopped, Mervyn flung open the door, and a flood of bracing air poured into the turret. Keen it was, but without the sting of the frost, and its sharpness was tempered by the warming rays of the sun. Stepping out on to the wet and glistening deck, Silas moored the vessel securely by her stern cable to a projecting pinnacle of ice, then turned and gazed about them.