See, we're standing on a solid floor--four feet of packed rock and cement.

The dynamite and black powder are under that.
We're in a chamber--a cave--an artificial cavern.

It's forty feet deep, twenty wide, and about seven high." He held the lantern even with his shoulders and walked deeper into the cavern as he spoke.

The others followed.

They passed a keg on which was a half-burned candle.