Henry and Paul looked curiously at the black mouth and they felt some tremors at the knowledge that they were to go in there, and to remain inside the earth for a long time, shut from the light of day.

It was the dark and not the fear of anything visible, that frightened them.
But they made no attempt to enter that evening, although night would be the same as day in the cave.

Instead they provided for a camp, as the horses and a sufficient guard would have to remain outside.

The valley itself was an admirable place, since it contained pasturage for the horses, while at the far end was a little stream of water, flowing out of the hill and trickling away through a cleft into another and slightly lower valley.
After tethering the horses, they built a fire near the cave mouth and sat down to cook, eat, rest and talk.
"Ain't there danger from bad air in there ?" asked Ross.

"I've heard tell that sometimes in the ground air will blow all up, when fire is touched to it, just like a bar'l o' gunpowder." "The air felt just as fresh an' nice as daylight when I went in," said Hart, "an' if it comes to that it will be better than it is out here because it's allus even an' cool." "It is so," said the master meditatively.