"All right, let's finish this job as soon as possible," Bud proposed, as he started toward a thicket of bushes and small trees a few yards from the landing place.

All being in harmony with this plan, there was a general move toward the interior. The thicket, however, proved to be only about twenty feet in depth, and beyond this was a clear area a quarter of an acre in extent.

"Somebody's had a camp here not many days ago," Cub announced, as he pressed forward eagerly toward the center of the open area.

"Yes, and a tent has stood right here," said Mr. Perry, indicating several guy-rope stakes driven in the ground.

"Whoever it was didn't leave more than a day or two ago," Hal declared.

"See how the gra.s.s is tramped down around here?"

"What's this?" exclaimed Bud as he ran back toward the thicket through which they had pa.s.sed and picked up a pole about ten feet long and two inches thick.

Mr. Perry and the other two boys rushed forward and made an eager examination of Bud's discovery.

"This looks interesting," said Bud significantly as he called attention to several worn places at both ends and the middle of the pole, as if with iron rings or wire held close around it under a strain.

"There's another just like this one over there," cried Hal, suddenly darting forward toward a slender pine tree about a hundred feet away and standing a short distance out from the thicket border of the open area.

Mr. Perry, Cub, and Bud rushed after Hal, who picked up, under the pine tree, a pole almost the exact duplicate of the one found by Bud. After a careful examination of them both, Mr. Perry announced:

"It looks to me, boys, as if you had discovered the spreaders of a demolished aerial."

"No doubt of it," Hal agreed. "Somebody used this tree and that one over there as masts of an aerial."

"But trees are not supposed to be good for aerial masts," Bud objected.

"They're all right if you have your insulation well out beyond the branches," said Cub.

"Yes, that's true," Bud admitted. "And look up there--see that wire? The fellow who took down this aerial didn't do his work very well."

All looked up in the tree and saw a wire hanging down among the branches and appearing to be attached at the farther end near the top of the pine.

"It was probably done in a hurry," Mr. Perry observed.

"And that is one more point to the argument that this is the island we were looking for," said Bud.

"Yes, but the fellow we came to rescue is gone and left no trace where he's gone to," added Cub.

"Still, don't you think the search has been worth while?" the latter's father inquired.

"I do," put in Hal, who had been noticeably quiet and meditative since the last very important discovery. "This makes it look as if that last distress message we got from the island was no fake affair?"

"Why?" asked Bud.

"Why!" flashed Hal. "It's plain enough to me. Those four fellows, he said were coming to attack him, probably overpowered him and swept away his camp, radio outfit, and all."

"And what did they do with him?" demanded Cub, eager for the last chapter of the plot.

Hal seemed about to make answer to this question, but something of the nature of a "lump in his throat" checked his utterance. His friends read his mind without difficulty.

"Never mind, Hal," said Cub with his bravest effort at consolation; "if the prisoner on this island was your cousin, we'll follow those enemies of his to the end of the world and make them give him up, won't we, dad?"

"Don't you worry too much over this affair, Hal," urged Mr. Perry by way of response to his son's extravagant a.s.surance. "If the person you got those messages from was your cousin, I don't believe the fellows who were after him had reason to do him any serious harm. But you may be sure that we will not leave a stone unturned in an effort to solve this--this--"

"Mystery," suggested Cub mischievously grasping at the opportunity to give his father a good-natured dig.

"Call it what you wish," smiled Mr. Perry. "But under any name you may be pleased to style this problem, we are going to go after it with some more mathematics--"

"And geography," interposed Cub.

"Yes, and geography, and you boys know what success we have had with mathematics and geography in this search of ours thus far. Now, meanwhile, I'm going to make a new suggestion which I hope you boys will look upon with favor. Let's establish a camp of our own right here on the spot where the Canadian Crusoe had his camp."

CHAPTER XII

Hal's Discovery

The boys were delighted with the suggestion of Mr. Perry that they establish a camp on the island and needed no urging to begin work on the project. With true outing instinct they had come prepared for just such an emergency as this. They had brought with them a tent large enough for four and a complete set of camp tools, including spade, shovel, axe, pickaxe, hatchet, saw, hammer, and nails.

Returning to the Catwhisker, they hauled all these supplies out on deck preparatory to taking them ash.o.r.e.

"Let's make a better ascent up this steep bank before we carry these things up," Mr. Perry proposed. "It's quite a climb, as it is, without a load in our arms to hamper us."

"Only one person can work at a time to any advantage," Bud suggested.

"That's true," replied the director of the expedition. "But we can work in rapid shifts and finish this job quickly. I'll take the first trick and make things fly for about fifteen minutes, and then one of you can take my place."

With these words, he stripped off his coat, seized the pickaxe and shovel and stepped over the side of the boat onto the landing ledge. Then he began a vigorous attack on the steep incline between the ledge and the land level above.

The task consumed a little more than an hour of speed labor, and by that time it was after one o'clock and each of the hillside stairway builders had worked up a very healthy appet.i.te. So they prepared and ate luncheon on board the yacht, and then began the work of moving tent and other supplies to the site selected for their camp. By the time this was done and the tent pitched, it was 3 o'clock.

"Now, what next?" asked Cub as he sat down on a camp chair after the last guy rope had been drawn taut and fastened securely to its peg. "It seems to me that it's about time for another pow-wow of the Catwhiskerites."

"I agree with you, Bob," said his father, also unfolding a camp chair and sitting down, followed by similar action on the part of the other two boys.

"Well, what's the question?" asked Bud.

"I'll offer a question if somebody'll take the chair and preside," Hal volunteered.

"All right," Bud agreed. "You act as chairman, Mr. Perry."

"I am elected by Bud, there being no opposition," announced the owner of the Catwhisker. "Now, what is the question, Hal?"

"I'll put it this way," the latter replied: "Resolved, that mathematics is more useful to a detective than a flashlight or a skeleton key."