"I'm coming, old fellow!" quivered the submarine skipper, starting to run.
Boom! A terrific explosion shook the ground. The air seemed full of flying fragments of rock.
CHAPTER X
"MR. GRAY" MAKES NEW TROUBLE
Had Jack Benson started down the slope two or three seconds later he must have been killed.
As it was, the fearful force of concussion sent him sprawling headlong on the ground.
A shower of small fragments of rock and of loose dirt fell about him.
Yet Jack was up again, like a flash, never stopping to inquire whether he had been hurt.
"O-oh!" came the groan, from Hal Hastings.
"There, in a second!" panted Captain Jack, beginning to run again.