“I heard a peculiar noise while you were speaking, but it is still now.”

“Birds—night-birds,” said Briscoe. “Our friends of the cavern grumbling because we’ve turned them out.”

“Oh, no; I don’t fancy it was that,” said Brace hurriedly. “It sounded like human voices singing in chorus.”

“Our fellows below in the boat,” said Lynton, “only they wouldn’t be singing.”

“Oh, no; it was not that,” said Brace.

“Might be anything,” said Briscoe, yawning. “Frogs, perhaps, down by the water-side.”

“No: I’m pretty well used to the night sounds we hear,” said Brace impatiently. “Ah, there it is: listen.”

He was silent, and as if reflected from the cliff there came a low musical sound, very soft and sweet, and, as he said, as if many voices were raised far away in a kind of chorus which reverberated from the sides of the cañon, reaching in a soft murmur to where they stood listening.

“H’m!” ejaculated Briscoe, after listening till the sound died softly away. “Can’t be any band having a concert on the next street.”

“And I should say it isn’t a boating party returning down the river from an outing, singing glees,” said Lynton.