Suddenly the old captain, who had been watching the smoke closely, gave an astonished snort.
"What's the matter, captain?" asked Rob, who was about to walk to the water's edge and get ready to shove off the dinghy.
"Why, there's somethin' queer about that thar smoke," responded the old salt.
"Queer—how do you mean?"
"Well, watch it a minute—there—see! now stops—now it starts ag'in—then it stops—wha, do yer suppose is happenin' to it?"
Rob knitted his brows and watched the phenomenon to which the captain had called attention with narrowed eyes.
There was no question about it the smoke was certainly behaving "queerly" as the captain put it.
The blue vapor emerged from the chimney now in a copious puff and then, for a space, would cease, only to roll forth once more in larger volume. The boys watched it in some astonishment.
"What can they be doing, do you suppose?" Merritt asked.
"I have no idea. It's past me to say," responded Rob, "it comes out in puffs like—like—by hookey! I've got it!" he broke off with a shout, "like the Morse code!"