There, listen again! You can hear a dull rumbling sound." "Yes, I can hear it," said Mark in an awe-stricken whisper.
"I dare say if we went on we should see some strange sights." "Without lights ?" said the captain, who had approached them silently.
"Perhaps we should get subterranean fire to show us the interior of the mountain.

What do you say ?--shall we explore a little further?
One does not get a chance like this every day." "I'm willing to come another time with lights, but it would be madness to go on in the dark.

How do you know how soon you might step into some terrible chasm ?" "Without the slightest chance of being shot out again, like Billy Widgeon!" said the major.

"You are quite right; it would be a terribly risky proceeding." They listened, and this time there came a low boom and a roar as if there had been an explosion somewhere in the mountain, and the roar was the reverberation of the noise as it ran through endless passages and rocky ways echoing out to the light of day.
"No, it does not sound tempting," said the major.

"I don't want to go far.