Jeff Stokes turned rather pale.

"What is the matter?" he gasped, steadying his voice as much as he could as the aeroplane began to drop steadily down toward the water beneath them.

"The gasolene's given out," rejoined Roy in a voice which was full of anxiety.

"Oh, Roy, what shall we do?"

Peggy gasped as the aeroplane, its propeller beating the air more and more feebly, began to descend with greater rapidity.

"We'll have to volplane to some land if we can, and if we can't we must take our chances for it in the water," was Roy's grim reply.

CHAPTER XII.

WHAT HAPPENED ON THE ISLAND.

"Look," cried Peggy suddenly, "isn't that a small island below there?

Maybe we can make that?"

"I'll try to," was the answer, as Roy gripped the steering wheel more firmly.

At the same instant the motor, with a gasp and a sputter, gave out altogether. But Roy knew how to volplane; that is, to reach the earth by swinging the aeroplane in circles so that her stability was maintained even with the power cut off.

He began to execute this maneuver now. The island which Peggy had indicated was a small spot of land some five miles off the sh.o.r.e. It was sandy and barren looking on one side, though at the further end from them there grew some trees and scrubby looking bushes.

If he could only keep the aeroplane from sagging down into the sea Roy was confident he could land at the place in safety. But it was still some distance off and the aeroplane was still dropping with much greater rapidity than seemed comfortable. Both Roy and his sister were expert swimmers, and the boy knew that Jeff was at home in the water. But at the same time, if they struck the surface of the sea, there was the chance that they might become entangled in the aeroplane and drowned before they had an opportunity to save themselves. So it was with a keen sense of apprehension that the boy exercised all the air craft of which he was master in bringing his sky cruiser downward.

"Oh!" cried Peggy suddenly as the Golden b.u.t.terfly gave a sickening downward drop like a stone plunging to vacancy.

But the empty "air pocket" which the craft had struck was a small one, and the next instant the atmosphere caught the broad wings and buoyed the aeroplane up from what seemed to be destined to be a disastrous fall.

The drop had, however, had one good effect. It had thrown the aeroplane almost on end, and in that manner drained a few last driblets of gasolene from the depleted tank into the feed pipes.

It was only a little fuel, but it was enough to cause the engine to resume operations for a couple of minutes. Taking advantage of this lucky accident, Roy drove forward, and as the propeller came once more to a standstill the Golden b.u.t.terfly sank down into a bed of sand which made her almost at once stationary.

"Well, we are--aerial Robinson Crusoes," exclaimed Peggy as, having clambered out of the cha.s.sis, she stood surveying the little island which they had so fortunately landed upon.

"Yes, and if we don't get some gasolene pretty quick we'll be Crusoes in a mighty uncomfortable sense," commented Roy, moodily gazing about at the surrounding sea, smooth as a sheet of gla.s.s and without the sign of a boat upon it. Far off on the horizon there hung a three-masted schooner, all her sails set, in the flat calm. But she was too far off to aid them even had she been able to.

"Tell you what we'll do, let's explore the island," said Jeff Stokes suddenly.

"Of course," cried Peggy, clapping her hands, "that's what everybody does in story books when they are stranded on a desert island, and right after that they always find just what they want, even down to a silver-mounted manicure set."

"I'd like to see a tin-mounted can of gasolene," grunted Roy.

Nevertheless after seeing to the engine of the aeroplane he was willing enough to set out with the others to explore this little spot of land in the Sound.

It was so small that it did not take them long to reach the summit of the low peak into which it rose in the centre.

"Oh, there's a little hut!" cried Peggy, suddenly.

Sure enough, below them, and half overgrown with tall weeds and scrub growth, was a half ruined hut. It was doubtless the relic of some fisherman who had once used the island as headquarters. But it had, apparently, long lapsed into disuse.

Hardly had they spied it before Roy made another discovery. Drawn up in a miniature cove not far from the hut was a trim and trig white motor boat, seemingly, from her long narrow shape and powerful engines, capable of great speed.

Here was a discovery! A motor boat meant gasolene and companionship.

With a soft cry of joy Peggy was dashing forward toward the hut, from which they could now hear proceeding the hum of human voices, when Roy suddenly checked her. From the doorway there had suddenly issued the figure of Morgan, the Bancrofts' butler. He gazed about him with a look of half alarmed suspicion on his flabby face. The young aviators instinctively crouched back behind a screen of green brush. They felt a suddenly aroused premonition that everything was not as it should be.

"H'its nothink," said Morgan, addressing someone within the hut, after he had gazed about a little more without seeing anything to further alarm his suspicions.

"All right, if that's the case come back in here," came another voice from inside the hut.

"Giles!" recognized the astonished Peggy. But another and a greater surprise was yet in store for them when they heard another voice strike into the conversation. There was no mistaking the tones for any others than Fanning Harding's.

"You chaps are nervous as kittens," he was saying, "who on earth would come to this island? We are as private here as if we were in the South Seas. Now go ahead, Morgan, with what you were saying."

"Well, what h'I says is this," spoke up the English butler, "a fair diwision and no favoritism. You say you want a third? You ain't h'ent.i.tled to h'it. H'it was h'only by h'accident that you found h'out h'our secret h'and h'I thinks you ought to be content with what you can get."

"Very well," was the rejoinder, "but as you fellows know, I've got you in my power. You daren't make a move without consulting me. If you try any monkey tricks I'll crush you so quick you won't know what struck you. The police are still carrying on their investigation, and----"

But here the voices sank so low that the eager young listeners could hear no more. But their eyes shone as they exchanged glances. Somehow both Peggy and Roy felt that the conversation had related to the mysterious vanishing of the jewels. This at least appeared clear from Fanning Harding's reference to the police.

"We'd better get back to the other side of the island before they come out and see us," counseled Peggy. "If they were to find out we had been spying on them they might get frightened and spirit the jewels away from wherever they have them concealed, for I'm just as sure now that they are all three mixed up in it as I am that--that----"

"We have no gasolene," put in Roy.

"But you have no proof and nothing to go upon," objected Jeff Stokes who was, like most folks around Sandy Bay, familiar with the details of the strange occurrence.

"That's just the trouble," said Peggy, "and it is just as impossible to go ahead in the case as it is for us to fly without fuel."

"Peg!" cried Roy, suddenly, "look at that!"

"That" was a ten gallon can of gasolene standing on the beach by the side of the motor boat. Evidently, to drag her bow up on the beach, they had lightened the craft so as to make the task easier, for several ropes, water jars and other bits of marine tackle lay about.

"If we could only get it," sighed Peggy.

"Yes, if," was the rejoinder from Roy, "but we can't steal it, and, as you say, it might spoil everything if Fanning Harding thought that we had overheard any of his talk."

"Look out!" warned Jeff Stokes in a whisper the next instant. The warning did not come a bit too soon. The door of the hut opened and the party which had been in conference inside emerged. They made straight for the motor boat, which Jeff Stokes had, in the meantime, recognized as one that was for hire at Sandy Bay.

"Come on, boys, we've got to be getting back," urged Fanning moving quickly and preparing to shove the craft off.

"Wait till I chuck some of this truck in," grumbled Giles.

He stooped and rapidly threw in the ropes and other gear scattered about.

Then as Fanning Harding and the flabby-faced butler shoved the craft off he made a hasty scramble for the boat's bow, leaping in as she floated free of the beach.