They could hardly realize it, yet the depth-gage1 told the story. It registered a distance below the surface of the ocean of five thousand seven hundred feet—a little over a mile. The Advance had actually come to rest on the bottom of the Atlantic.
"Hurrah2!" cried Tom. "Let's get on the diving suits, dad, and walk about on land under water for a change."
"No," said Mr. Swift soberly. "We will hardly have time for that now. Besides, the suits are not yet fitted with the automatic air-tanks, and we can't use them. There are still some things to do before we start on our treasure cruise. But I want to see how the plates are standing3 this pressure."
The Advance was made with a triple hull4, the spaces between the layers of plates being filled with a secret material, capable of withstanding enormous pressure, as were also the plates themselves. Mr. Swift, aided by Mr. Jackson and Captain Weston, made a thorough examination, and found that not a drop of water had leaked in, nor was there the least sign that any of the plates had given way under the terrific strain.
"She's as tight as a drum, if you will allow me to make that comparison," remarked Captain Weston modestly. "I couldn't ask for a dryer5 ship."
"Well, let's take a look around by means the searchlight and the observation windows, and then we'll go back," suggested Mr. Swift. "It will take about two days to get the stores and provisions aboard and rig up the diving suits; then we will start for the sunken treasure."
There were several powerful searchlights on the Advance, so arranged that the bow, stern or either side could be illuminated6 independently. There were also observation windows near each light.
In turn the powerful rays were cast first at the bow and then aft. In the gleams could be seen the sandy bed of the ocean, covered with shells of various kinds. Great crabs7 walked around on their long, jointed8 legs, and Tom saw some lobsters9 that would have brought joy to the heart of a fisherman.
"Look at the big fish!" cried Mr. Damon suddenly, and he pointed10 to some dark, shadowy forms that swam up to the glass windows, evidently puzzled by the light.
"Porpoises," declared Captain Weston briefly11, "a whole school of them."
The fish seemed suddenly to multiply, and soon those in the submarine felt curious tremors12 running through the whole craft.
"The fish are rubbing up against it," cried Tom. "They must think we came down here to allow them to scratch their backs on the steel plates."
For some time they remained on the bottom, watching the wonderful sight of the fishes that swam all about them.
"Well, I think we may as well rise," announced Mr. Swift, after they had been on the bottom about an hour, moving here and there. "We didn't bring any provisions, and I'm getting hungry, though I don't know how the others of you feel about it."
"Bless my dinner-plate, I could eat, too!" cried Mr. Damon. "Go up, by all means. We'll get enough of under-water travel once we start for the treasure."
"Send her up, Tom," called his father. "I want to make a few notes on some needed changes and improvements."
Tom entered the lower pilot house, and turned the valve that opened the tanks. He also pulled the lever that started the pumps, so that the water ballast would be more quickly emptied, as that would render the submarine buoyant, and she would quickly shoot to the surface. To the surprise of the lad, however, there followed no outrushing of the water. The Advance remained stationary13 on the ocean bed. Mr. Swift looked up from his notes.
"Didn't you hear me ask you to send her up, Tom?" he inquired mildly.
"I did, dad, but something seems to be the matter," was the reply.
"Matter? What do you mean?" and the aged14 inventor hastened to where his son and Captain Weston were at the wheels, valves and levers.
"Why, the tanks won't empty, and the pumps don't seem to work."
"Let me try," suggested Mr. Swift, and he pulled the various handles. There was no corresponding action of the machinery15.
"That's odd," he remarked in a curious voice "Perhaps something has gone wrong with the connections. Go look in the engine-room, and ask Mr. Sharp if everything is all right there."
Tom made a quick trip, returning to report that the dynamos, motors and gas engine were running perfectly16.
"Try to work the tank levers and pumps from the conning17 to............