than Dora's and Dorothy's canoe. The others cheered the
pretty girls as they forced their craft through the rippling water. The
management of a canoe--especially a double canoe--is not so easy as it
appears. But the Lockwood twins had taken to that form of aquatic sports
very kindly, and there really were few canoe crews in Centerport who
handled their craft as well.

The fleet of boats crossed the lake in a short time and, headed by the
twins' canoe, reached the eastern end of the island. They swept into the
cove where the girls had seen, the previous Saturday, the rough-looking,
bewhiskered man upon the shore. Right here under the Boulder Head was
the mouth of the cavern from which the island obtained its name.

As the twins swept their canoe on with easy strokes, Dora suddenly
uttered a cry of excitement.

"See there, Dory!" she said.

"See where?" demanded her sister, craning her neck to see over Dora's
shoulder.

"There! Down in the water! The sunken boat!"

The water in the cove was very clear, but it had considerable depth. The
canoe was brought sharply up by the two girls and both peered down.

Below them could plainly be seen a sunken rowboat. It did not appear to
be damaged in any way, but had simply filled and sunk.

"What have you found, girls?" demanded Lance Darby, whose boat was
nearest to the twins' canoe at the moment. "Is there some deep sea
monster down there?"

"Come and look, Lance," cried Dora.

The moment the young Darby saw the submerged craft he exclaimed:

"Here it is, by gracious!"

"Here is what?" demanded Laura.

"The boat. Hey, Chet! we've found it!" he called to his chum, who
quickly turned his own boat's prow in their direction.

"What you found?" demanded Laura's brother, coming nearer.

"Here's Mr. Norman's boat that he lent Short and Long," declared Lance,
eagerly. "It was just as you said, Chet. Billy came over here to the
island."

"Oh, my!" cried Jess. "And if that is so, perhaps he is still here."

"We must find him," said one of the twins, earnestly. "His sister Alice
is just about worried to death about him; and the longer he remains in
hiding, the worse it will be for him, anyway."

CHAPTER XII

IN THE CAVE

The other boats of the flotilla began to make the cove and soon there
was a loudly chattering crowd around the sunken boat.

"Are you sure that's the old rowboat Billy got from Mr. Norman?" asked
one of the other boys of Chet.

"Yes, sir