“But if they capture our steam yacht how are we to get away from here, even if we do uncover the treasure?” said Sam.

“We’ll get away somehow—­and make it good and hot for them in the bargain,” answered Tom, and his father nodded in approval.

With their thoughts on the Rainbow and those on board, the treasure hunters went back to the vicinity of the shattered cave.  Nobody felt much like working, yet to remain idle made the time hang heavily on their hands.

“There is no use of our going to work in a haphazard fashion,” were Mr. Rover’s words.  “We must first go over the ground carefully and plan out just what is best to do.  Otherwise a good portion of our energies will be wasted.”

This was sound advice and was followed out.  They surveyed the whole vicinity with care, poking in among the rocks with long sticks, and turning over such as were loose and easily moved.

“This looks as if it was going to be a long winded job,” was Sam’s comment, and he heaved a sigh.  “I thought we’d come here, march into the cave, and put our hands right on the gold and diamonds!”

Dick was a short distance away, poking into a hole with a stick.  The stick was over eight feet long, but the end did not appear to touch anything.

“There is some kind of a hollow below here,” he said to the others.  “I think we ought to investigate and see how large it is.”

The others agreed with him, and all set to work to pull aside half a dozen rocks which were in the way.  They had to use all their strength and even then the largest of the stones refused to budge.

“Let us get a small tree and use it for a pry,” suggested Mr. Rover.

They had an ax with them, and Tom cut down the tree and trimmed it.  Then, resting the log on one stone, they inserted the end under the big rock and pressed down with all their might.

“She’s coming!” shouted Sam, as the big stone commenced to move.

“Yes, and look at the opening underneath,” added Dick.  “It must surely be part of the cave!”

The sight of the big hole made all eager to know if it was really a portion of the shattered cave and they worked on the big rock with renewed energy.  Twice it slipped back on them, but then they got a new purchase and over it went and rolled out of the way.  Then all of the treasure hunters got on their hands and knees to gaze down into the hole.

“It must be part of the cave,” said Mr. Rover.

“I’ll climb down on the rope,” said Tom.  “Hurry up, I can’t wait!”

“You be careful, Tom, or you’ll get hurt,” warned his father.  But it must be confessed he was as eager as his son to learn whether or not they had discovered the treasure cave.

Tom went down, and Dick and Sam came after him.  The bottom of the hole was rough.  On one side was another opening, leading to what certainly looked like a cave of considerable extent.