This news was true, and as the rockets and Roman candles hit the rowboats and the occupants the latter stopped rowing and then began to back water in confusion. Soon the rowboats turned back and hastened to the side of the _Josephine_. "That's what I call repelling boarders!" said Captain Barforth, grimly. "I only hope the fireworks hold out." "It is now to be a race between the _Rainbow_ and that other craft," observed Mr. Rover, and he was right. Inside of fifteen minutes both vessels were headed out to sea, and running at about the same rate of speed. Soon the haze over the water hid both craft from view. "Well, one thing is certain," said Mr. Rover. "Our friends are alive to their danger and are going to do their best to get away from the enemy." "And another thing is that we are left marooned on this isle," said the captain. The party remained in the tree a while longer, and then, as there seemed nothing else to do, they descended to the ground. "Well, we have one thing in our favor," was Dick's comment. "Sid Merrick and his crowd must be on the _Josephine_, or they wouldn't chase the _Rainbow_, and that being so they can't interrupt our treasure hunt, at least for the present." "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.