"Down on your faces!" called Tom to those with him in the cabin. "Lie down, every one! The freshest air is near the floor; the bad air rises, being lighter with carbonic acid. Lie down!"

All obeyed, Tom following the advice he himself gave. It was a little easier to breathe, lying on the tilted cabin floor, but how long could this be kept up? That was a question each one asked himself.

"Is every bit of our reserve air used?" asked Tom, speaking to Earle.

"As far as I can learn, yes, sir. If I had known that the auxiliary tank was empty I wouldn't have ordered the compressed air motor used. But I didn't know."

"No one is to blame," said Tom in a low voice. "It is one of the accidents that could not be foreseen. If there is any blame it attaches to me for not installing the gyroscope rudder. If we had had that when we were caught in the cross current, or the whirlpool swirl, our equilibrium would have been automatically maintained. As it is--"

He did not finish, but they all knew what he meant.

"Bless my soda fountain, Tom!" murmured Mr. Damon, "but isn't there any way of getting fresh air?"

"None without rising to the top," Tom answered. "We'll have to try that. Come with me to the engine room, Mr. Earle. It may be possible we can pull her loose."

They started to crawl on their hands and knees, to take advantage of the purer air at the floor level. The situation of the M. N. 1 was exactly the same as it had been when she ran into the mud bank in the river, with the exception that now she was in graver danger, for the supply of air for breathing was almost exhausted.

Reaching the engine room, where he found the crew lying down to take advantage of the better air near the floor, Tom made a hasty examination of the apparatus. There was still plenty of power left in the storage batteries, but, so far, the motors they operated had not been able to pull the craft loose from where her nose was stuck fast.

"Are the tanks completely emptied?" asked Tom.

"As nearly so as we could manage with the pumps not acting to their full capacity," answered Earle. "If we could turn the craft on a more level keel we might empty them further, and then her natural buoyancy would send her up."

"Then that's the thing to try to do!" exclaimed Tom, his head beginning to feel the heaviness due to the impure air. "We'll move every stationary object over to the port side, and we'll all stand there, or lie there, ourselves. That may heel her over, and help loosen the grip of the sand."

"It's worth trying," said Earle. "Get ready, men!" he called to the crew.

Tom crawled back to the main cabin and told Mr. Damon and the others what was to be attempted.

"Koku, you come and help move things," requested Tom.

"Me move anything!" boasted the giant, who, because of his great strength and reserve power did not seem as greatly affected as were the others.

Going back to the engine room with Koku, Tom assisted, as well as he could, in the shifting of pieces of apparatus, stores and other things that were movable. They all worked at a great disadvantage except Koku, and he did not seem to feel the lack of vitalizing air.

One thing after another was shifted, and still the M. N. 1 maintained the dangerous angle.

"It isn't going to work!" gasped Tom, as he noticed the indicator which told to what angle the craft was still off an even keel. "We'll have to try something else."

"Is there anything to try?" asked Earle, in a faint voice. He was on the point of fainting for lack of air.

Tom looked desperately around. There was one piece of heavy machinery that might be moved to the other side of the engine room. It was bolted to the floor, but its added weight, with that of the crew and passengers, together with what had already been shifted, might turn the trick.

"Let's try to move that!" said Tom faintly, pointing to it.

"It will take an hour to unbolt it," said one of the men.

"Koku!" gasped Tom, pointing to the heavy apparatus. "See if-- see if you--"

Tom's breath failed him, and he sank down in a heap. But he had managed to make the giant understand what was wanted.

"Koku do!" murmured the big man. Striding to the piece of machinery, the legs of which were bolted to the floor, Koku got his arms under it. Bending over, and arching his back, so as to take full advantage of his enormous muscles, the giant strained upward.

There was a cracking of bone and sinew, a rasping sound, but the machinery did not leave the floor.

"Him must come!" gasped the giant. "One more go!"

He took a hold lower down. Tom's eyes were dim now, and he could not see well. Some of the men were unconscious.

Then, suddenly, there was a loud, breaking sound, and something tinkled on the steel floor of the submarine engine room. It was the heads of the bolts which Koku had torn loose. Like hail they fell about the giant, and in another instant the big man had pulled loose the machine, weighing several hundreds of pounds. In another moment he shoved it across the floor, toward the elevated side of the craft.

For a second or two nothing happened. Then slowly, very slowly, the M. N. 1 began to heel over.

"She's turning!" some one gasped.

An instant later, freed by this turning motion from the grip of the sand bank, the submarine shot to the surface. Up and up she went, breaking out on the open sea as a great fish darts upward from the hidden depths.

It was the work of only a few seconds for the man nearest it to open the hatch, and then in rushed the life-giving air. Tom and his companions were saved, and by Koku's strength.

"Me say him machine got to come up--him come up!" said the giant, smiling in happy fashion, when, after they had all gulped down great mouthfuls of the precious oxygen, they were talking of their experience.

"Yes, you certainly did it," said Tom, and due credit was given to Koku.

"Never again will I travel without a gyroscope," declared Tom. "I'm almost ready to go back and have one installed now."

"No, don't!" exclaimed the gold-seeker. "We are almost at the place of the wreck."

"Well, I suppose we can travel more slowly and not run a risk like that again," decided Tom. "I'll put double valves on the emergency air tank, so no accident will release our supply again."

This was done, after the broken valves had been repaired, and then, when the machine Koku had torn loose was fastened down again, and the submarine restored to her former condition, a consultation was held as to what the next step should be.

They were in the neighborhood of the West Indies, and another day, or perhaps less, of travel would bring them approximately to the place where the Pandora had foundered. The latitude and longitude had been computed, and then, with air tanks filled, with batteries fully charged, and everything possible done to insure success, the craft was sent on the last leg of her journey.

For two days they made progress, sometimes on the surface, and again submerged, and, finally, on the second noon, when the sun had been "shot," Tom said:

"Well, we're here!"

"You mean at the place of the wreck?" asked Mr. Hardley.

"At the place where you say it was," corrected Tom.

"Well, if this is the place of which I gave you the longitude and latitude, then it's down below here, somewhere," and the gold-seeker pointed to the surface of the sea. It was a calm day and the ocean was the proverbial mill pond.

"Let's go down and try our luck," suggested Tom.

The orders were given, the tanks filled, the rudders set, and, with hatches closed, the M. N. 1 submerged. Then, with the powerful searchlight aglow, the search was begun. Moving along only a few feet above the floor of the ocean, those in the submarine peered from the glass windows for a sight of the sunken Pandora.

All the rest of that day they cruised about below the surface. Then they moved in ever widening circles. Evening came, and the wreck had not been found. The search was kept up all night, since darkness and daylight were alike to those in the undersea craft.

But when three days had passed and the Pandora had not been seen, nor any signs of her, there was a feeling of something like dismay.

"Where is it?" demanded Mr. Hardley. "I don't see why we haven't found it! Where is that wreck?" and he looked sharply at Tom Swift.