The dirigible had by this time settled so badly that she was barely twenty feet above the wave-tops.

Some sacks of ballast still remained, kept by Frank for an emergency.

He now was compelled reluctantly to give the order to cut these away and one by one they dropped overboard; but as they did so, the ship rose and an hour later they landed on a smooth beach.

The island did not seem to be of great extent, but to the delight of the adventurers, from the midst of the cocoanut grove that crowned the islet there flowed a tiny stream of clear water. This was indeed a G.o.dsend, as they did not know how long they might have to remain there. With a spade, which formed part of the dirigible's outfit--"I suppose they figured on shoveling out the treasure," laughed Harry--a small basin was soon dug out for the water to settle in and make a sort of small well, from which it could be dipped out for cooking and drinking purposes.

Fortunately the larder of the dirigible was well stocked, and as they were two mouths short they were not in any immediate fear of hunger.

That evening, when arrangements for sleeping and keeping watch for any pa.s.sing steamer or vessel had been made, Constantio beckoned to Frank and asked him to join him in a walk along the beach. The lad, nothing loath of a chance for exploration, started off with the Spanish inventor, who seemed to be anxious to confide something to him.

"You are worried about getting away from the island?" he said.

"I am--yes," rejoined Frank, "you see our gas is exhausted and I for one can't figure out but we shall stay here till some one comes along and picks us up. Unless we can build a raft out of the remains of the dirigible."

"Oh, make yourself easy about that, my dear young friend," exclaimed the inventor. "I can refill the gas-bag and that without delay, but--but--well, to be frank with you, how much is it worth to you if I do so?"

Frank was amazed at the sudden proposal and no less astonished at the Spaniard's boast that he could inflate the dirigible.

"What do you mean?" he asked. "I confess I don't altogether understand you."

"I thought I had made myself clear," was the reply. "I have changed my mind since I spoke to you last about the treasure, and now I feel that I am ent.i.tled to some of it if I can refill the dirigible."

"Why, yes," said Frank, with a laugh; "of course you are IF you really can."

"Would five thousand dollars' worth of ornaments or doubloons seem too much?" ventured the Spaniard.

Frank broke into a loud laugh.

"Why, no; you shall have that, and gladly, if you think you can help us to get out of this place."

"Thank you," said the inventor, quite seriously, "I don't want more than my just dues, but I certainly am ent.i.tled to that."

"Oh, certainly," laughed Frank, much amused at the man's deprecatory manner. "What is your plan?"

"Well, senor," said the Spaniard, "I have a certain amount of my gas-producing powder left in my cabin. There is none too much, but enough, I think, to inflate the dirigible with--at any rate, to fit her for flight to the mainland, which cannot be so very far off."

Frank nodded.

"There are some empty cylinders on board," went on the inventor. "All that is necessary to do is to put equal parts of sand, water and my powder into the cylinders and then screw on the caps to produce almost pure hydrogen gas at tremendous pressure. You follow me?"

"Yes," said Frank, "when can we do this?"

"Why, to-morrow morning," was the reply. "The actual inflation will take but little time."

As they returned to their camp they found it in a state of great excitement. Two of the men, in strolling about the island, had found lying up in a small cove, where it seemed to have drifted, a ship's boat.

There was no clue as to how it had come there, but on its stern were painted the words "Falcon, New York."

"I'll bet a lemon that it's one of the ship's boats of the Falcon that I read about been missing this year," exclaimed Ben; "it's got oars in it, too, they say. They are lashed under the seats, so that it must have broken loose from the ship when she went down and been washed ash.o.r.e here. We can get away in the boat if nothing better offers."

Frank drew him aside and explained to him Constantio's plan for reinflating the gas-bag.

"We will try that, and if that plan fails then we can take to the boat," said the boy.

Ben agreed that if the air-ship could be inflated it would be much better to fly to land in her than to set out under the tropical sun in an open boat, not knowing where they might land.

The camp was so arranged that night that the treasure was placed near to the boys and Ben, while the three members of the dirigible's crew, her engineer and Constantio slept at some little distance.

Had the boys seen the gleam that had come into the inventor's eyes at the discovery of the boat they would not have been so trustful of him when he volunteered to take the middle watch of the night. As it was, however, they little imagined the plot that had formed in the fellow's head. While the boys and Ben slumbered, however, he drew aside the engineer and Wells, the red-headed sailor, and the three rapidly stocked up the boat with water from the spring in kegs and jars taken from the dirigible and laid in a supply of provisions. Then they awakened the other two men and explained to them in low whispers the plan to escape from the island they had formed.

"We will get all the treasure and divide it," whispered the cunning inventor. "If the boys wake while we are getting it to the boat, don't hesitate to attack them. We are stronger in numbers and can beat them off."

The other two readily agreed, more particularly as the inventor told them that it was the boys' intention to keep all the treasure for themselves in the event of their getting ash.o.r.e in the dirigible.

Before the boat had been found the inventor had been willing enough to aid the boys, but with the discovery of that means of escape his plans had undergone a change. He saw a way to appropriate the entire ma.s.s of treasure.

CHAPTER XXV.

THE FIGHT ON THE ISLAND.

Silently as cats the plotters approached the pile of treasure sacks when they judged that the time was ripe for their raid on the valuables. Constantio, who was a coward at heart, had taken his station by the boat so as to be the furthest away from danger should the boys be aroused.

With a beating heart he waited the appearance of the first heavy bag of treasure. At last the engineer and one of the sailors came in sight dragging it over the top of a sand dune.

"Phew, that's heavy," exclaimed the sailor, who was our red-headed friend, Wells, setting the bag down with a sigh. "How far is it from the camp to this boat, Mister Concertina?"

"Not more than a few hundred yards," replied Constantio; "I don't see what a big strapping fellow like you is making so much fuss over packing a fortune that little distance."

"It's a wonder you wouldn't tackle the job yourself," said Wells indignantly, as he and the engineer heaved the sack into the boat. "I guess you are scared though. I always knew that Spaniards were cowards."

Infuriated as much by the truth of the insult as stung by the stigma it conveyed, Constantio, pale with fury, sprang at the sailor with his knife drawn. He sprang back again with the same agility and crouched on his haunches like a tiger-cat, as the sailor whipped out a revolver and leveled it at him.

"Now you be careful what you are doing, Concertina," he said, "or I'll have to send you where you won't make no more trouble."

As he spoke there came a loud report from the direction of the camp.

It was followed by another and another.

"They have discovered us!" cried Constantio, seizing hold of the boat and trying to drag it off.

At the same instant the two sailors, who had been left behind to bring a second sack of the treasure, appeared, racing over the top of the sand dune.

"They heard us as we were moving the sack," cried one of them; "something jangled, I guess, and--"

"They awakened and fired at us,--see here," he held up a bleeding arm, "broke my elbow I guess."

"Come on," shouted Wells, "we are playing for too big a stake to let two boys and an old man beat us off. Who is for coming back and driving them off?"