IITHEY MADE GOOD TIME. The clean air acted as a tonic, and hope spurred them on. The tunnel sloped upward rather sharply, and presently Harker heard water, a low thunderous murmur as of an underground river up ahead. It was utterly dark, but the smooth channel of stone was easy to follow.
Sim said, "Isn't that light up ahead?"
"Yeah," said Harker. "Some kind of phosphorescence. I don't like that river. It may stop us."
They went on in silence. The glow grew stronger, the air more damp. Patches of phosphorescent lichen appeared on the walls, glimmering with dim jewel tones like an unhealthy rainbow. The roar of the water was very loud.
They came upon it suddenly. It flowed across the course of their tunnel in a broad channel worn deep into the rock, so that its level had fallen below it
