A stream of smoke was issuing from the fieldstone chimney roughly constructed at one end of the apparently deserted dwelling.

“There’s some one living in that bungalow,” he exclaimed, as he made the discovery, “maybe whoever it is can give us some clue to where Joe Digby is.”

They all gazed intently at the weather-beaten old house from which the paint was scaling, adding to the note of desertion sounded by its closed shutters and forlorn-looking yard.

As they looked, astonished at the idea that the barren structure should actually house a human being, a sudden thought struck Merritt.

“Suppose Jack Curtiss and his gang are there?” he said.

“Hardly likely,” rejoined Rob, “however, we’ll get over there and find out just who is making that smoke.”

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!”

“Somebody signaling?” stammered Merritt.

“That’s it—­watch!”

The smoke, which had not been visible for some seconds, now emerged from the stone chimney once more and the boys, fascinated, watched it closely with burning eyes.  There was no doubt whatever about it now.  It was signaling.

Four short puffs.

“Four dots—­that’s H,” exclaimed Rob, trembling with excitement.

The smoke ceased.

“Here comes some more,” shouted Merritt.

One short puff from the chimney.

“E, one dot, that’s E sure enough,” translated Rob.

The others stood like figures carved in stone as their leader read off the strange signals.

Puff!  A longer period of smoking by the chimney—­then two sharp puffs.

“That’s L,” interpreted the leader of the Eagles.  Before they could say a word the chimney took up its message once more.

Puff—­a long puff—­another long one, and then a short one.