"Yes," said Will; "carried here and there by the wind." "Well," said the artist, "the water makes roaring noise enough, without our listening for echoes. Let's go a bit higher where we can see the sky. It's horribly dark down here, but the stars are very bright if we get out of the shadows. What's the matter?" he said sharply, for Will caught his arm. "There it is again," cried the boy. "Somebody must be hammering and thumping. What can it be?" "It's what I said," said Josh; "the bearings of the big wheel are a bit loose. Who could be hammering and thumping in the darkness? Wouldn't he have a light?" "I don't know," said Will; "but if something's got loose, it ought to be seen to." "But you couldn't do anything in the dark," said Josh. "My word, what a game it would be if the old wheel broke away! What would happen then?" "Once started, I should say it would go spinning down the valley for miles," said Manners, laughingly. "Just like a Brobdingnagian boy's hoop gone mad." "Ah, I should like to see that by daylight," cried Josh. "I shouldn't," said Will, bitterly. "It wouldn't be much fun. There! now, can you hear it? That thumping?" "Yes, I heard it then," said Manners, "and I don't think that there's any doubt of its being the echo of something giving a thump as the wheel turns. Is it worth while to go and tell old Jack-of-all-trades Drinkwater to come and see if anything's wrong?" "No," said Josh. "I don't believe he'd come." "Perhaps it's nothing to mind," said Will, thoughtfully; "only, working machinery is such a ticklish thing. There, I can't hear it now." They stood listening for quite ten minutes, but the unusual sound was not renewed. "Perhaps it's somebody in the mill," said Will. "Let's go down and look." "All right; anything to fill up time," said Manners, "before we get my eels. There's no occasion to go up here." They descended cautiously through the darkness to the mill-yard, following Will, who made straight for the door leading into the machine-room, the fastening yielding to his hand, for few precautions were used in the shape of bar or bolt in that quiet, retired place; and, as the door swung back, the three stood gazing into the darkness before them, listening and feeling. The whole building seemed to thrill with the vibration caused by the turning wheel, the weight of the water making the entire building quiver as if it were alive. "Rather weird," said Manners. "I never was here before at such a time. Does the place always throb in this way?" "When the wheel is going fast," replied Will, "it gently shakes the biggest beams." "Sounds as if it might shake the place down in time." "Oh, no," said Will; "it's too solid for that." "Well," said Josh, "there's nobody doing anything here. If there was, there'd be a light. It was only echoes. Come along." "But if it was echoes," said Will, "why did they leave off?"