had struck a tiny water course between the rocks. And now the very bottom of it seemed to drop out, and they sank down and down into almost utter darkness.
"We are lost!" spluttered Dick, but it is doubtful if either of his companions heard him.
For the minute after Dick was so dazed and bewildered that he said nothing more. He clutched at rocks, dirt, and tree roots, but all gave way at his touch.
At last he found himself flat on his back on a heap of dead leaves and moss. Partly across him lay Larry, while Peterson was several feet away. Around the three lay dirt and bushes and several good-sized stones. It was lucky the stones had not come down on top of them, otherwise one or another might have been killed.
"Gosh, what a tumble!" ejaculated Peterson, when he could speak. "I told ye to be careful. This island is like a reg'lar honeycomb fer holes."
"Oh, my foot! " gasped Larry, as he tried to get up.
"That was a tumble and no mistake," said Dick. "What's the matter with your foot, Larry?"
"I don't know, excepting I must have sprained my ankle," was the answer. "Oh!" And Larry gave a loud groan.
Forgetful of their situation, Dick and the lumberman bent over Larry and helped him to get off his shoe and sock. His ankle was beginning to swell and turn red, and he had sprained it beyond a doubt.
The water was coming into the opening from the little stream overhead, and Dick readily procured a hatful of the fluid and the ankle was bathed with this. After this it was bound up, and Larry said it felt somewhat better.
"But I can't walk very far on it," he continued, and then added, with a sorry smile, "I am laid up, just as the Rocket is!"
"The question is, now we are down at the bottom of this hole, how are we going to get out?" said Dick to Peterson.
"We'll have to get out some way," was the unsatisfactory response. "See, the water is coming in faster than ever."
The lumberman was right, the water had been running in a tiny stream not larger than a child's wrist; now it was pouring in steadily like a cataract. Soon the bottom of the hole had formed a pool several inches deep.
"Wait till it fills up and then swim out," suggested Larry.
"No, thanks," returned Dick. "We might be drowned by that operation."
The hole was irregular in shape, about ten feet in diameter and fully twenty feet deep. What had caused the sudden sinking was a mystery until it was solved by the water in the pool suddenly dropping away into another hole still deeper. Then of a sudden the trio went down again, this time at an angle, to find themselves in a good sized cave, where all was dark and uncertain.
The tumble had wrenched Larry's ankle still more, and the youth could not suppress his groans of pain.
As soon as he was able Peterson leaped up, struck a match, and lit some brushwood which happened to be near and which the water had not yet touched.
By this light Larry's ankle was again attended to and bound up in a couple of handkerchiefs.
"If we keep on we'll get to the center of the earth," remarked Dick, as he gazed around curiously. "Where do you suppose we are now?"
"In one of the island caves," answered Peterson. "I told you the place was full of them. That's the reason the smugglers used to hold out here."
"Perhaps we'll come across some of their treasures."
At this Peterson shook his head. "Not likely. When the last of the smugglers was arrested the government detectives searched the island thoroughly and gathered in all to be found."
"I see. Well, how are we to get out, now we are down here?"
"We might climb back, Rover, the way we came, but that is dangerous on account of the water. I rather think we'll do better to look for the regular opening to the cave, if there is any."
The matter was talked over for several minutes, and it was decided that Dick and Peterson should investigate, while Larry remained by the fire, keeping it as bright as possible and resting his sore ankle.
At a short distance ahead the cave branched into two parts, and coming to the forks, Dick took the right while Peterson moved to the left. Dick carried a torch, which he held overhead, and likewise a pistol, in case any snake or wild animal should attack him.
The youth had not proceeded far before he came upon signs which showed that the cave at one time had been inhabited by human beings. First he espied a part of an old bag, then a weather-beaten sailor's cap, and soon after a rusty pistol, falling apart for the want of care.
"This must have been a smugglers' retreat sure," he murmured to himself. "My, if I should stumble across a box of gold!"
He hurried forward and presently reached a spot where the cave broadened out into a round chamber. Here there were a rude table and several benches, all ready to fall apart from decay.
With quick steps he approached the table, for he had seen something lying upon it something which made him start and give a cry of wonder. In the center of the table was a heap of silver dollars, and beside this was a land map, drawn by hand. On the map lay a rusty dagger and a human skull!
CHAPTER XXIII
THE BAXTERS ARE FOLLOWED
"Well, I never!"
Dick gazed at the silver, the map, the dagger, and the skull with mingled surprise and horror.
How had those things come there, and what was the mystery concerning them?
Coming closer, he picked up several of the dollars and examined them. All were dated thirty to forty years back.
Then he picked up the dagger, a beautiful affair of polished steel with a curiously wrought handle of buckhorn.
The skull he left untouched.
The map was covered with dust, some of which he endeavored to blow away. Beneath he saw that there were odd tracings of many kinds, and letterings in a language which was strange to him. Then his light began to go out and he shouted for Peterson to join him.
The sound echoed and re-echoed throughout the cavern, showing that the place was even more roomy than he had anticipated. He waited several minutes, then saw Peterson's light.
"What's up?" demanded the lumberman as he approached. "Find anything important?"
"I should say so," answered Dick. "Look there."
Peterson did so, then gave a cry of astonishment.
"Silver, lad, silver! And a skull!"
"There is some story hidden in this affair," said Dick soberly. "Can you explain it?"
"I cannot." Peterson picked up the dagger. "That's a French weapon."
"But
