He was thus engaged when he first observed a movement in the shadow of the thicket to the south of his position.  Then, indeed, he congratulated himself on the preparation he had just made to defend himself and his companions against stealthy and hostile movements on the part of the enemy about the camp under cover of the darkness.

Bud was not, by nature, a blood-thirsty boy.  All of these preparations for battle were made without the slightest thought of the actual effect of one of his missiles should it hit his mark.  His industry was inspired more by the mechanical act than by any picture of human pain that might result.  Hence, when the time came for him to make use of his weapon “with deadly intent,” he found himself in a hesitant frame of mind.  He knew that some animal, human or otherwise, was eyeing the camp with studied interest, and it was difficult to imagine other than a human being capable of such interest.

Bud finally came to the conclusion that the animal half hidden in the shadow of the bushes was a man, and that the latter’s interest was centered in “Captain” Howard, whom he doubtless believed to be held prisoner within the four canvas walls of the tent.

“I bet he’s one of those four men that took Hal and me and marooned us on that other island,” the boy mused.  “Of course, he’s looking for a chance to set our prisoner free, but he’s doomed to disappointment.  My goodness!”

Bud whirled around suddenly as a new possibility occurred to him, stimulated by a slight noise like the cautious tread of a man’s foot.  The next instant a cry of alarm almost escaped him as he saw a human form near the entrance of the tent.

“My goodness!” he repeated aloud, but in subdued tone, as he recognized the approaching youth.  “You’d better announce yourself, Max, before you come onto an armed person under such circumstances as these.”

“Armed!” echoed the Canadian youth in surprise.  “I thought Mr. Perry said—­”

“Oh, yes, he said we couldn’t have his automatic, but I’ve been busy making a very effective substitute since I came out here—­see?”

Bud exhibited his weapon by drawing back the leather sling, thereby stretching the elastics to their full capacity.  His searchlight he had switched off after finishing the work on his catapult, and the only illumination in the open area came from the moon over the tree tops.

“Did you make that out here to-night?” demanded Max in astonishment.

“Sure—­why not?” was the other’s reply.

“Well, you’re some boy, all right.  I’d never ’ave thought of it.  If anybody means mischief around here, he’d better look out, with a weapon like that in your hands.”

“You bet he had,” Bud returned with a sturdiness of purpose, indicating to his Canadian friend that he meant business.  “And there’s at least one prawler around here already.  I’m glad you came out here, for I was just about to come in and wake up the whole camp.”