“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 assurance.  “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.”