Early the next morning all were aboard. To each one was assigned a particular station. Washington, with Mark as an assistant, was in the engine-room. Jack was to watch the various gages and registers to give warning of any danger. The professor, of course, would be in the conning tower and operate the craft. Andy was to be with him, to watch out, with his sharp eyes, for any danger that might loom up in the path of the searchlight. Tom and Bill were to be ready to help where needed.
With a hissing sound the water filled the tanks and the Porpoise sunk beneath the waves. The engine that worked the endless screw was started, and the threads, working on the water cable, shot the boat ahead.
"We're off!" yelled Washington.
About sixty feet below the surface the craft was sent along. Mile after mile was covered as shown by the patent log. The lights were turned off, and through the thick plate glass windows the strange inhabitants of the sea were observed.
"I think I'll go a little nearer the surface," said the professor to Andy. The inventor started the pumps that emptied the tanks. The craft rose slightly.
"Quick! Stop her!" shouted the old hunter, grasping the captain's arm.
Something black, like a grim shadow, loomed up in the dull glare of the searchlight.
"What is it?" cried the professor.
"We're goin' to hit somethin' hard!" yelled Andy.
"It's the hull of a ship!" exclaimed the inventor as he jammed the reversing lever hard over.