On that basis, namely, of twenty-five guns, ten rounds would mean two hundred and fifty sh.e.l.ls, and it was then considered that the most important thing would be to utilize the time of two for the purpose of making the sh.e.l.ls. This was the most laborious process, as every step had to be done by hand, the dies being in the form of separate punches, held and driven by hand, as they had no such thing as a press for manipulating the dies.

One morning Harry said: "I know it isn't the proper thing to suggest it while we are all so busy making the preparations for the expedition, but I think we ought to make a trip to the cave before we start."

Neither of them objected to the proposal, and George went to the Professor, and told him that he and Harry had conferred on the subject of the cave, and with his permission they would take the boys there.

The Professor's a.s.sent was given with a smile of pleasure, and several lamps were put into condition for the event. All was excitement now with the young spirits, and the Professor a.s.sisted them in the preparations.

It did not take long to reach the mouth of the cavern, and lighting the lamps, descended slowly. Neither George nor Harry had informed the boys of the treasure within the cave, nor of the skeletons which were discovered, although, when the boys had asked the source of the skeletons in the laboratory enough of an evasive answer was given to make them suspect the source, and this was confirmed when Harry told them, days before, that they had also discovered a cave.

They descended the steps, and made their way along the pa.s.sage leading to the first recess. As the chamber came into view the boys were entranced at the sight. It was a novelty to them. It was the first time they had ever witnessed such a thing.

To Harry and George it was no longer a thing to marvel at. They were veterans in the exploring field.

"This makes a fellow feel queer in here," exclaimed Tom, as he glanced around at the magnificent stalact.i.tes.

"Did we tell you," replied George, "about the mysterious thing that happened to us the second time we came in?"

"No; what was it?"

"We entered from the other opening by the sea."

"Another opening? Do you mean that this cave has two openings just like the one John spoke about?"

"Yes; but this is a mighty long one, and it had a lot of water in it twice when we visited it, but I don't think we shall find any here now."

"Why not?"

"Because we have not had much rain for the past month."

"But you forgot about the mystery."

"That's so; we went in from the other end and had gone up nearly to where the water began, when we put one of the lights on a ledge, and went forward with the other, and when we had gone about a hundred feet, it disappeared, and we have never found it to this day."

"That does seem odd. Do you think it was taken by some one?"

"Well, we could not possibly account for it in any other way but that it fell off the ledge by some accident. How that could be possible I don't know, as George declared he had placed it in a secure position."

By this time they had reached the recess, and George suggested that the entire cave should be examined, and Ralph was somewhat in the lead.

Everywhere was the universal whiteness of the calcareous deposit. As they reached the vicinity of the chests, where the copper vessels were, they formed a striking contrast to the whiteness all around.

"What are those things there?" asked Tom, stepping back in surprise, pointing to the vessels.

Ralph peered forward, to get a better view. "It looks like kettles of some kind."

Harry pa.s.sed the boys and walking up to one of the kettles, overturned it, and as a shower of the coins slid out, and rolled about, they were amazed beyond all description.

Ralph was the first to recover, and he picked up some of the coins: "Didn't you know about these? I believe they are gold; look, Tom. Did you ever see anything like this?"

Tom was stupefied. "I don't wonder that men will risk their lives to get treasure like this. Here we didn't hunt for it and we found it."

"Yes, but Harry and George knew all about it; didn't you?"

And the boys laughed an a.s.sent.

"Why don't you take it out of here?"

"Well, it seems to be pretty safe in this place; and if we should have been attacked by the natives, we should have a place of retreat and have our treasure with us."

After putting the coins carefully back, Harry said: "Probably we may be able to discover something else." And he moved forwardly to the right, with Tom following close, and the boys pressing up to see what else might be found. There, at the place where the Professor had deposited them in a row were the five skeletons, and they presented such a ghastly sight that they shrank back in horror.

"We found these in a little different position when we first arrived."

"In what way?"

"They were in all sorts of positions in front of the recess, and some of them had the knives still sticking in their ribs, and one or two, one of which the Professor has, had a big bullet in the skull, which we took out and can show you."

"Where did you find these?"

"Right in front of the place where the treasure was found."

"Well, did they have a fight, do you think, for the possession of the treasure?"

"Undoubtedly."

"Now, let us go around to the other side of the cave."

It will be remembered that in the other portion of the cave the skeletons and the treasure, as well as the weapons, were left just as they were found by the boys, because they had never informed the Professor of their secret visit to the cave, when they discovered the chained captives and the skeletons about them.

The party pa.s.sed around the first projecting wall which separated the two large chambers, and as they were moving along something sounded in the second chamber ahead. The boys stopped suddenly. In a moment more the same peculiar dull and ominous sound was continued, and it seemed to be very near.

The boys looked at each other in amazement. During all of the previous visits there had never been the slightest sound within the cavern.

"Possibly," said Harry, "it may be running water."

"It doesn't sound like water to me. I will--" but Harry did not have an opportunity to say anything more, as a terrific roar, like a cannon shot, rang out, and the boys were simply petrified.

"What do you think that was?" whispered George. They drew close together, and spoke in whispers.

"This will never do," declared Harry. "If there is anything in this place we might as well know it now as later. Will you join me in the hunt?"

And the boys responded with one a.s.sent. "Let us go to the second chamber. Come on, boys." And they bravely stalked down the corridor.

When the chamber was reached a hollow laugh greeted them, followed by two hearty laughs. The Professor and John had entered the opening at the sea end, and hurriedly made their way to the second chamber, where they awaited the coming of the boys.

The boys were intensely relieved, and the Professor was so happy to see the determined and resolute spirit they manifested, that he complimented them highly.

John was no less profuse in his commendations. "I want to say, that men can be brave when they know what they have to fight, and who their enemies are; but it takes the stoutest heart to go forth and defend yourself, or a.s.sume the offensive against an unseen and an unknown enemy."