With the colored man to help them the two boys, by the use of the ammonia, succeeded in reviving Bill, Tom and old Andy. But the professor, probably on account of his advanced age, did not respond so readily to the treatment. The boys were getting quite alarmed, as even some of the diluted ammonia, forced between his lips, did not cause him to open his eyes, or increase his heart action. “If he should die, and leave us all alone with the ship in this terrible place, what would we do?” asked Jack. “He’s not going to die!” exclaimed Mark. “Here I have another plan. Washington bring that medical electrical battery from the engine room.” This was a small machine the professor had brought along for experimental purposes. Quickly adjusting it, Mark placed the handles in the nerveless fingers of Mr. Henderson. Then he started the current. In about a minute the eyelids of the aged inventor began to quiver, and, in less than five minutes he had been revived sufficiently to enable him to sit up. He passed his hand across his forehead. “What has happened?” he asked in a faint voice. “I don’t know; none of us knows,” Mark answered. “We all lost our senses when it got so hot, and there seemed to be some peculiar vapor in the air. The last I remember was seeing some horrible shape rush from the storeroom, soon after the ship struck. Then I fainted away. When I woke up I managed to turn the lights on, and then I came back here.” “I wonder where we are,” the old man murmured. “I must find out. We must take every precaution. Washington, go and look at the gage indicating our depth.” The colored man was gone but a few seconds. When he returned his eyes were bulging in terror. “What is it?” asked Mr. Henderson, who, thanks to the battery, had almost completely recovered. “It ain’t possible!” gasped Washington. “I’ll never believe it!” “What is it?” asked Mr. Henderson, while the others waited in anxiety for the answer. “We’re five hundred miles down!” declared Washington. “Five hundred miles!” muttered the inventor. “It does not seem possible, but it must be so. We fell very rapidly and the terrible draught sucked us down with incredible rapidity. But come, we must see what our situation is, and where we are. We are stationary, and are evidently on some solid substance.” They all felt much recovered now, and, as the terrible fright of being consumed in a fiery furnace had passed, they all were in better spirits. At the suggestion of the professor, the boys and Washington made a tour of the ship. They found, for some unaccountable reason, that nearly all the engines and apparatuses were out of gear. In some the parts had broken, and others were merely stopped, from the failure of some other machine, on which they were dependent. “I’m afraid this is the end of the _Mermaid,”_ said Mark, in a sorrowful tone. “Nonsense!” replied Jack, who was of a more cheerful nature. “Things are not so bad as they look. The professor can fix everything.”