Frank gave an exclamation and started for the stairs.

“What is that you say, Barney?” he cried.

“Shure, sor, the lake has gone!”

Frank gave a loud shout.

“Heigho, Beere!” he cried, “the time for action has come. We are just in time. The lake has gone out.”

“Eh—w—what?” sputtered the captain, rolling out of his berth. “You don’t mean that?”

“Yis, sor, for I saw it wid me own eyes!” cried Barney, “shure, cum up an’ ye kin see fer yersilf.”

The captain leaped into his trousers. Then he sprang up the cabin stairs with Frank.

In a moment all were at the rail. Then there was an astounded silence.

Barney’s hair fairly rose on end. He gazed down below, then up at the sky, then around him. Then he gasped for breath.

“Mither av Moses! Did ye iver see the loikes! Shure it has cum back agin!”

Both Frank and the captain looked sharp at the Celt.

There below them was the sparkling surface of the lake. It presented just the same appearance and was just as high as when they had last seen it the night before.

“Barney,” said Frank, severely, “have you been drinking?”

The Celt stuttered and stammered and acted very foolish. But he managed to say:

“Be me sowl, Misther Frank, it was gone, and not an hour since, sor. I saw the sand an’ the rocks ’an’ all, sor!”

Frank and Nicodemus exchanged glances.

“What time was it when you discovered the disappearance of the lake, Barney?” asked Nicodemus.

“About two o’clock av the mornin’, sor!”

“Tell us all about it.”

Barney did this. Frank and the captain listened with interest. When he had finished Nicodemus said:

“Frank, there is no doubt of it. The lake went out and came back again while we were asleep.”

“It must be so,” agreed the young inventor.

“Shure, sor, it’s thrue,” averred Barney.

“Why didn’t you wake us up and tell us about it?”

“On me worrud, sor, I niver had a thought that it wud cum back again, sor, an’ I med out to wait until mornin’ rather than disthurb yez sleep, sor.”

“Well,” said Frank, turning to Nicodemus, “it is hardly likely that we could have accomplished anything anyway in that brief time.”

“That is true,” agreed the captain. “We will wait for another evacuation of the lake basin.”

All that day the little party watched the lake. That night all sat up until late to see if the lake would go out again.

But it did not. The next day brought no change, and thus several days passed.

Still the same smooth expanse of water smiled upon them every morning.

There seemed no reason for believing that it ever would or could change its basin.

A week passed thus.

Waiting and watching of course grew extremely monotonous. So after awhile diversions were indulged in to pass away the time.

Hunting trips were made into the interior of the mysterious country.

Many strange things were seen, and once a glimpse was had of a mighty cavern mouth far up in the hills, in which there were grouped a dozen of giant men.

They were no doubt of the giant race which inhabited those mountains. It seemed as if they must be fully seven feet in height and of enormous build.

Our adventurers took good care to keep out of their way, for a collision with them might not be pleasant.

Two weeks drifted by.

Then the first of a series of thrilling events occurred.

Nicodemus arose early one morning and walked around the far shore of the lake.

He was pacing the sands abstractedly when his eye caught something in the sand.

He paused with a gasp.

It was a footprint.

Moreover it was that of a man who wore a hobnailed boot. It could only prove one thing.

Others were in the region and they were also from civilization. Words cannot express the captain’s amazement.

“By Neptune,” he muttered, “how did they ever find their way to this out of the way place?”

Then other queries came to him. Who were they? What brought them here, and how many were in their party?

The captain’s curiosity was aroused.

Prudence bade him return to the air-ship and secure the co-operation of his companions. But powerful curiosity overruled discretion.

He bent down over the trail and followed it. A little further on as he had expected, the footprints met with others. For two miles he followed them along the shore.

Then he turned an angle in the shore and came upon a startling scene.

This was a camp in the verge of a clump of palms. A dozen brawny men in white shirts, loose trousers and sombreros, were sitting about smoking and talking.

All the paraphernalia of a camp, with a train of mules, was behind them. They had apparently been on the spot for some while.

Words can hardly express the sensations of the captain.

He stared at the scene, and then a sharp ejaculation escaped him.

“By Neptune! it is Jerry Dooley!”

His gaze was fixed upon a man who stood in the edge of the camp talking with three others. He was a man of smooth face, shifting gaze and stealthy manner. His appearance was that of a sea-faring man.

In him Nicodemus recognized one of the crew of the wrecked ship, who had been a companion of his at the time that the lake came back, and as Nicodemus had always believed, had drowned the entire crew left at the mound of gold.

But there had been one exception. This was Jerry Dooley, the ship’s steward. As fate had it, he had started himself right after Nicodemus and Langley to go back to the camp on an errand. He was overtaken by the waters of the lake, but dashed high and dry upon an eminence on the lake shore.

Dooley had made ineffectual search for the camp, and not finding it, finally started back for the Pacific coast.

After many hardships he reached it and pluckily put to sea in the ship’s boat left there. Good fortune became his.

He was picked up by a coaster bound for Valparaiso and later got a berth aboard an American ship of the line. Later he went into the navy.

But he had never forgotten the Transient Lake and the mound of gold. He believed all his companions dead.

He succeeded in the navy and became a lieutenant, finally being retired on half pay. Having the leisure time he now decided to carry out a long-cherished desire.

This was to pay a visit again to the Transient Lake, and if possible recover the buried treasure. He succeeded in organizing a party.

For a year they had floundered about in the swamps of Paraguay, and finally crossed the wild ranges of Chuquisoca, and by a stroke of luck found the lake.

And here they were encamped and waited for precisely the same thing that the aerial voyagers did, viz: the disappearance of the lake.

This much Captain Nicodemus guessed. He was so excited at the outlook that he inadvertently stood out in full view of the camp.

And just then Dooley, chancing to look up, saw him.

He gave a start and for a moment his face was livid. Then he started toward Nicodemus.

The captain saw that he had betrayed himself, so he did not attempt to conceal himself. Instead he advanced to meet the other.

“Dooley!” he exclaimed; “on my word, this beats all. I thought you dead.”

“And I thought you dead, skipper,” declared the lieutenant.

“What—when—how—what are you here for?”

The lieutenant looked sharply at the captain. In that moment each understood the other.

“I have come back for the gold in the bottom of the lake,” said Dooley.

The captain stiffened visibly.

“You have!” he exclaimed.

“Yes.”

“Do you expect to get it?”

“Not unless the lake again changes its basin.”

“Oh, umph! Let me see. Were not your companions drowned when the lake returned that time?”

“They were.”

“But you—how did you escape?”

Dooley told his story. Then he asked sharply:

“But how did you get here? You have not been here ever since?”

“Hardly,” replied Nicodemus, quietly. “I have come here for the same purpose as yourself, for the buried gold.”

“Ah!”

The two men gazed at each other. In that moment antagonism was uppermost.

“I suppose that gold belongs to whomever can recover it.”

“Certainly not!” replied Nicodemus.

“Indeed!” said Dooley, somewhat staggered. “How do you disprove that?”

“Easy enough. My right to it is indisputable, and confirmed by the law of prior discovery. The gold is mine!”

Dooley drew a deep, sharp breath. Matters were becoming strained.

“I disagree with you,” he said.

“Eh?” roared Beere.

“I do not agree with you.”

“What do you mean?”

“Just this: We have as much title to that gold as you. It was to have been equally divided at the time. It shall be so now.”

“By what authority?” asked Beere.

“The authority of fair play. We have come thousands of miles, have dared death in every form, and we are not in a mood to sacrifice the prime object of our expedition.”