If only one man had arrived at the cavern he might be frightened and driven away by a little shooting. With bullets whizzing through what was left of the opening, the man who was building the crude wall would not be likely to present his body before the space still uncovered. This reasoning brought the boy to a consideration of the matter of ammunition, but he decided that, with the cartridges carried by Frank, they could defend the place for a long time.
But another question intervened. The rocks which, though unseen, he knew to be blocking the space where the rug had hung were undoubtedly falling from a distance. They might have been stored above the natural doorway for the very purpose to which they were now being put.
If this were true, then the building of the trap would continue, regardless of his bullets. While he studied over this problem, slowly making up his mind to put it to the test, Frank’s voice came from the tunnel again.
“What’s doing out there?” the boy asked. “Why don’t you come in here?”
“Shut off your light!” ordered Ned, as a glimmer showed inside.
“Not me,” replied Frank. “I need all the light I can get in here!”
“What have you found?” asked Ned anxiously.
Frank did not reply instantly, and Ned heard the rattle of stones while he waited for his answer. The task of piling up the wall was progressing rapidly, and it seemed to the boy that the stones were all falling from a distance.
“Shut off your light and come out,” Ned said, impatient at the hesitation.
“I wouldn’t stay here in the dark for a thousand dollars a second,” Frank replied, “but I’ll come out. Why don’t you show a light?”