But unobserved by them all the while the passage had been trending upward. As good fortune had it they had chosen the only safe and sure way out of the reef.
Suddenly a dazzling light shone forth far ahead.
“The Dart!” gasped Bell, joyfully. “We are saved!”
It was truly the submarine boat.
A few moments later they came out of the cavern, and were in plain view of the boat.
They saw that the cave from which they emerged was only one of many which they had passed in their way from the boat some hours before.
For they had been a long time absent from the Dart.
Indeed, so long that Frank had become greatly worried, and had even donned his diving suit preparatory to going out to search for them.
But just as the young inventor was about to go forth Barney cried:
“Dere they are, Misther Frank!”