“And I can’t leave the light,” said Josh; but, as they spoke, the artist was in full pursuit, seeing as he did that a delicious morsel was going to save itself from being turned into human food.

There was a quick trampling faintly heard on the wet stone floor, followed by a rush, a glide, a heavy bump, and a roar of smothered laughter.

“Yes, it’s all very fine, young fellows,” growled the artist, as he gathered himself up; “a nasty, slimy beast! I tried to stop him with my foot, and it was like the first step made in a skate. Has it gone?”

“Gone? Yes,” cried Josh. “Never mind; there are plenty left. They’re awful things to hold. He would have got away all the same.”

“Not if I’d had a good grip,” said Manners.

“I don’t know,” said Will. “He might have got a good grip of you. Those big ones can bite like fun. Are you very wet?”

“Bah! Abominable mess. This floor’s covered with slime.”

“Shall we stop any longer?”

“No,” said the artist; “I’ve had enough for once. Let’s get out in the open air again, and try and find out what made your noise.”

In a few minutes they were back on the top of the great stone wall that held the waters back, listening in the darkness amidst the rush and roar of sluices and chute, supplemented by the distant thunder of the heavy falls high up the stream, for the peculiar thumping whose repetitions had caught Will’s ears.