Charley noted the fact with satisfaction. "The solution of our mystery must lie on one of these two islands," he declared, "and the chances are in favor of this one, so here goes to discover it," and he plunged into the timber with Walter close at his heels. He had taken no more than twenty steps when he stopped with an exclamation of surprise and astonishment, his way was barred by a great wall of stone that towered several feet above his head. It had once been a fortification of considerable strength, but growing trees had made breaches in it here and there, their thrusting, up-growing trunks tumbling its blocks to the ground, where they lay hidden by covering vines.
"Whew," whistled Walter as he readied his chumps side, "who could have built this? It could hardly have been done by the Seminoles."
"No," said Charley, who was examining the strange wall carefully, "this stone is all limestone, which is found only along the coast or at a great depth. It has been brought here from a considerable distance. Indians may have done the work, but they never did it willingly. If they did it at all, it was as slaves. But we have no time for idle speculation. Let's walk along it and see how far it extends."
But after forcing their way along the wall for almost a quarter of a mile, at the expense of a good deal of exertion, they gave up the task.
"I believe it extends clear around the island," Walter declared, "we can't spare any more time to follow it up; it's noon already. Let's see what is inside."
Charley offered no objection, and the two boys climbed through a gap in the wall and reached the great enclosure.
At first glance, they could see but little difference between the dense growth amongst which they stood and that outside the wall, but a closer examination showed that, while the timber was very thick, it was of smaller size than that which they had left behind.
"This was a clearing at one time, years and years ago," Charley said, "see, there is an ironwood stump there that still shows the signs of an axe. It takes generations and generations for one of those stumps to rot."
"Look, Charley," cried his chum who had pushed a little ahead, "just see this."
A couple of strides brought Charley to his side, "A road," he cried in amazement.