"What is this place anyhow?" asked Tom, seeking to change the embarra.s.sing subject. "Was it an underground prison?"

"I think it was a burial place of some tribe," replied Jim, when he was able to control his laughter. "You see the skeletons are all standing up in like positions as if they were placed there after death."

"What are the bats doing in here?"

"They must come in through these pa.s.sages above. Some holes probably let out onto the side of the hill, and the bats go in and out through them at night."

"I think," said Tom, as they made their way back to the entrance, "that taking all together, that was the worst scare I ever had."

"Shake on that, Tom," said Jo.

A further search through the cave was fruitless of results, so far as looked for treasure was concerned, and their original plan of investigating the smoke signal was taken up.

A walk of another mile brought them to the spot they sought. They had thus far encountered no one, or any indication of the presence of inhabitants on the island. They gained finally the summit of the hill from which the column of smoke was ascending. They found that this had been made by building a fire in a small chimney of stones and covering it with wet leaves. There was an opening below which gave just sufficient draft to keep the fire smouldering.

But little could be seen of the land from the top of the hill on account of the thick woods, but by climbing one of the taller trees, which they did in turn while the others kept guard, they were enabled to make out that they were on an island of many miles extent, and that another island lay some five or six miles to the southwest. Most unexpected of all their discoveries, they saw in the distance far out upon the ocean a steamer which was apparently approaching the island. The distance was too great to determine with any definiteness anything about her character or probable intentions, and further information on that point would have to be sought at a later time.

"I can't understand that smoke business," said Tom, once more examining the chimney-like arrangement curiously. "It was certainly made by someone, yet there doesn't seem to be anyone about."

"They may be on the other side of the island," suggested Jim, "or they may have come from the other island and gone back again."

"But why should they have come over here and made the fire?" persisted Tom.

"You will have to ask them," laughed Jim. "I am sure I don't know, or why they should have lighted it at all. But some of us had better return to the ship or I am afraid that the professor will be getting anxious."

Arriving at the landing place, Tom elected to go on board. He felt that he had had enough of excitement and adventure for one day. Jim accompanied him, while Jo and Juarez, the spirit of investigation awakened, promptly set out on an exploring expedition returning however without incident at nightfall.

"Well," began the professor that evening when they had gathered on the deck awaiting the supper call, "what did you find out about the island to-day?"

"Not much of importance," replied Jim, "except that it is of very considerable extent, very rugged and mountainous."

"But Jo had an awful scare," broke in Tom.

"You mean you did," protested Jo.

"How was that?" asked the professor.

"Why, we found a cave with the entrance way up in the air. We thought at once that it was the one we were looking for, but it did not turn out to be," explained Tom. "And then we found a lot of skeletons in there, and they got after us."

"The skeletons did?"

"Well, something did," replied Tom with a grin. "Then Jo and I beat a hasty retreat."

"Each got hold of the other in the dark," explained Jim, laughing, "but I guess they had a jolly time of it till they broke away and ran. It sure was funny."

"Are you certain there wasn't anything unnatural in there?"

"We couldn't find anything alive except some bats, when we went back,"

replied Tom, "although we hunted all over."

"What kind of a place is it?"

"The cave?"

"No, the island."

"It seems to be an uninhabited island as far as we could see," answered Jim.

"Didn't you discover any signs of people at all?"

"Yes," replied Jim. "The same sign we saw from this deck. The smoke signal."

"That cave will bear further investigation. It is certainly very curious," mused the professor.

"What is?" queried Tom.

"About that smoke on the mountain."

"What do you think of it?" asked Jim.

"It is a signal of some kind, but if the island is uninhabited, who could have made it?"

"Why couldn't the ones who made it come from some other island?" asked Jim.

"And gone back again," suggested Jo.

"Perhaps so," replied the professor, "but that doesn't make it any clearer."

"You never can see through smoke very well," suggested Jo.

"True," laughed the professor, "but still somehow I don't like it."

"Then we saw a ship in the distance, apparently headed for this island, but far off the southern sh.o.r.e."

"Six o'clock," broke in Tom, as four bells were struck. "I think I will accept the invitation to dine."

"A good plan," commended the professor, "and Monday we must get an early start and learn, if we can about that ship you saw, and begin a more thorough exploration."

"I think so, too," replied Tom.

"What?" asked Jim.

"Take more 'rations' with us," replied Tom.

"Wake up, boy," cried Jo, giving him a shove and toppling him over on deck. "You think so much about rations that you are getting irrational."

"That gives me an idea," began Juarez, when Jo and Tom had been separated and quiet restored.

"An idea of war?" asked Berwick.