In the excitement of the moment, Dave's shotgun went off, the charge passing directly between him and his companion.
After falling about twenty feet, the mass of brushwood became wedged tight for a moment, and stopped descending.
"Oh!" came from Dave. "Now we are in a pickle. How are we to get out?"
For the moment they scarcely dared to move.
Then Bob took a step forward and the young diver did the same.
Instantly the mass began to sink once more, at first slowly and then as rapidly as ever.
Down they went—thirty feet, forty, fifty, sixty—a hundred, until the top of the hole was lost to sight and they found themselves they knew not where.
Again the brushwood and moss became wedged fast. But now they did not dare to move for fear of dislodging it once more.
"We are lost!" came from the engineer. "We'll never get out of this alive!"
"Don't give up yet," answered Dave, bravely, yet his heart felt like a lump of lead in his bosom.