“Do you know how high the tide rises on this island?” asked Andy after a pause. His voice sounded strange in that hollow, dark place, amid the ceaseless lapping of the water on the rocks.

“How high? No, but it can’t get much higher,” answered Frank as cheerfully as he could. “It’s been rising some time now, and it must stop soon.”

“It seems a long time, but it isn’t,” went on Andy in that quiet voice. “Look, it’s seven o’clock,” and he held out his watch, illuminating it with the flashing electric light.

“Seven in the evening,” murmured Frank. “It must be getting dark outside.” It had been dark from the beginning in the cave.

“Seven o’clock in the evening,” went on Andy, “and we came in here about four! The tide has several hours to rise yet, and—”

He did not finish, but he glanced down at the water that was steadily rising up on their legs.

It was chilling them, yet they dared not move much for fear of toppling off the narrow ledge.

Frank did not answer. He was busy trying to think of some way of escape. Yet, rack his brain as he did, no way out of the cave seemed possible. Were they doomed to die there?

“Can we climb any higher?” asked Andy, after another period of silence. “If we could, we might get out of reach of the water, even when the tide is full. Let’s turn on both our lights and look at the wall back of us.”

They had been saving the fast-waning current in the electric lamps against the time of need. They might have but little further use for it, so both Andy and his brother pressed the springs that turned on the gleaming lights.

In the glow they could see the black and gurgling water at their knees. It was swirling around from the force of the tide outside that was rushing into the cave. Though the stone thrown down by the man at the entrance prevented our heroes from escaping, the bowlder did not fit so tightly but what water could come in.

“Now to see what’s back of us,” spoke Frank, turning around as well as he could on the small shelf, and flashing his light on the wall behind him.

“Say!” suddenly exclaimed Andy, “doesn’t it strike you that the water isn’t coming in so fast as it was?”

Frank held his light lower, and looked at the rising tide.

“There doesn’t seem to be quite so much force to it,” admitted the elder Racer lad, “but I’m afraid that’s only because it’s higher, and because it has to wind in and out of so many passages, and force itself under and around the rock which that scoundrel threw down. I wish we had him here!”

“I guess he’s far enough off by this time,” remarked Andy. “But let’s see if there’s a way to get higher up.”

Together they examined the wall of the cave against which they had been leaning. Frank uttered a cry of joy.

“It’s mostly dirt, not stone!” he exclaimed. “We can cut steps in it, and climb up. Maybe we can get high enough so that the tide won’t reach us, or at least we can keep our heads above water until it goes down. Come on, where’s your knife?”

Working by turns, with the only knife available between them, the boys began frantically cutting niches or steps in the dirt wall. Fortunately it was packed hard enough so that it did not crumble. They took turns at the desperate labor, one holding the torch, and the other wielding the knife.

All the while the tide kept coming higher, until it was now to their waists. But they had not yet made enough notches to enable them to stand up, clinging by their hands and toes. For it needed four niches for each lad—eight laboriously-cut holes in the wall, four niches for the hands and four for the feet, some distance apart. Even when this was done it would only raise them about twenty inches. Would that be enough?

“We can’t cut any more after this,” said Frank dully, when they had almost finished the eight.

“Why not?”

“Because we can’t hold on in these and cut any more. The footing isn’t good enough. If we only had a sort of platform to stand on, we could reach up higher. As it is, I’m afraid this isn’t going to do much good—that is for very long. The water is still rising.”

“If we only had some sticks,” exclaimed Andy hopelessly. “We could drive them in the dirt, leaving the ends projecting, and then we could go up, like on a ladder.”

“But we haven’t any sticks.”

“Maybe there are some on the shelf where we are standing; imbedded in it.”

It was a slim chance, but worth trying, and by turns they stooped over and felt down beneath th............