No one answered. The experience, utterly new to them all, was sufficiently terrifying to destroy the desire for conversation. Shut up in this tiny shell which might any moment prove their tomb, fifty feet below the surface of the ocean, driving forward blindly into the unknown, it would have taken one braver--or more callous--than any there to make merry. Howard, used as he was to submarine work, might have cheered them up, had he not been compelled to give all his attention to driving the vessel. For the dangers, though not what the rest vaguely conceived, were by no means imaginary. Let the Seashark rise a few feet above the level at which she ran, and she might easily smash herself against a more than ordinarily deeply sunken wreck. Let her plunge too deeply, and the increased pressure of the water might force its way in at some weak spot, and crush her like an egg-shell. Let her power give out too soon, at a spot where she could not come to the surface to run her gas-engine, and so replenish her accumulators, and they would all perish miserably. On Howard rested all the responsibility, and he had no time to give to anything else. XVIII ONE, two, three hours slid by, and, at last, Howard, his eyes fixed on the gage of the accumulators, saw that the power was getting low, and began to watch anxiously for some gleam of light that, striking down through the water, might show a break in the mantle of weed overhead. In vain! Everywhere blackness ruled. Several times he slowed down and turned off the headlight, hoping that, with its effulgence removed, he might see the longed-for gap. After each attempt he went back to driving the Seashark along at her maximum eight miles an hour. This could not last forever. Rapidly his anxiety grew. The Seashark had been beneath the water for four hours, and his accumulators were nearly bare. To try to break through the weed was dangerous, but not more so than to remain below until all the power was gone. At all risks they must reach the surface. For a scant ten minutes longer Howard held on, now very close beneath the mantle of weed, then stopped altogether, and waited for the reserve buoyancy of the Seashark to carry her upward. Slowly she rose again, and then into the weed. Howard could see its slimy fronds through the thick glass of the conning-tower. Slowly and more slowly it seemed to brush downward as the Seashark worked herself upward. Slowly and more slowly until all motion ceased, leaving the vessel still far below the surface. With a shrug of his shoulders, Howard pulled a lever, and in quick response came the throb of the pumps beneath him as with powerful strokes they drove out the water-ballast and made the Seashark lighter. Under this new impulse she rose once more, little by little, until at last the pumps sucked dry and motion ceased once more. Howard, peering upward, saw the light faintly gleaming through the interstices of the weed. The surface could be scarcely a yard overhead.