For a moment or so no one seemed to know what answer to make to Laddie. He stood there, all out of breath, looking at his father and mother and Grandma Bell, who were sitting on the side porch.  
"What—what did you say?" asked Mr. Bunker.
 
"It's Russ," Laddie answered. "He's going and he can't stop! I tried to make him, and he tried himself, but he can't stop, and he's running like anything!"
 
"What in the world does he mean?" asked Mother Bunker.
 
"Tell me about it!" said Grandma Bell.
 
"It's out in the barn," explained Laddie. "Russ got on something, and he can't stop running!"
 
"Maybe he's in a trap!" exclaimed Laddie's mother.
 
"If he was in a trap he couldn't run," said her husband. "I'll go out and see what it is."
 
The other little Bunkers were still playing with Muffin, the big gray cat, as Mr. and Mrs. Bunker and Grandma Bell hurried out to the barn.
 
As they drew near it they heard a voice shouting:
 
"Oh, make it stop! Make it stop going! I'm so tired! My legs are so tired!"
 
At the same time a low rumbling¹ could be heard, like that of very distant thunder.
 
"Oh, what is it?" gasped² Mother Bunker. "Oh, Russ, what have you done now?"
 
But a moment later they were all relieved to see Tom, the hired man, come to the door of the barn, leading Russ by the hand. The boy looked frightened, but not hurt.
 
"What was it?" asked his father.
 
"I got to going and I couldn't stop," explained Russ, who was breathing almost as hard as Laddie had done after his run.
 
"What did you get to going on, and why couldn't you stop?" his mother wanted to know.
 
"Oh, it was a—a sort of wooden hill," explained Russ. "I was running on it and——"
 
"What does he mean—a wooden hill in the barn?" asked Mrs. Bunker.
 
"It was the treadmill³," explained Thomas Hardy⁴. "I was in another part of the barn, and I guess Russ must have wandered upstairs, where we keep the old treadmill they used for the threshing machine and churn. He started to walk on the wooden roller platform, and it moved from under him. He had to keep running so he wouldn't slip down. That's what he meant when he said he couldn't stop."
 
"That was it," explained Russ. "I saw a funny machine upstairs in the barn, and I got on it. I didn't know it would move."
 
"Well, you couldn't get hurt on it, that's one good thing," said Grandma Bell. "At the same time it's better not to get on queer machines, or play with things you don't know about, Russ. The next time you might be hurt."
 
"I'll be careful," promised the little boy.
 
"What is the treadmill?" asked Vi, who had come out to the barn to see what all the excitement was about.
 
"It's a sort of engine," Grandma Bell explained. "You see out here, years ago, when Grandpa Bell ran the farm, we didn't have gasoline engines such as are now used in automobiles⁵ and for pumps and other farm work. So we had to use a sort of engine that one or two horses could make go. It was called a treadmill, and some were made so that even dogs, trotting⁶ on a moving wooden platform, could work a churn. We used to have one of those, but the one Russ got on was a treadmill for one horse."
 
"I saw it," said Laddie. "Russ wanted me to get on, but I wouldn't. He did and then he couldn't stop. He couldn't stop running!"
 
"That's right!" exclaimed Russ. He could laugh now, as he remembered what had happened. "Then I told Laddie to run and get somebody to help me," he added.
 
"I ran, but I didn't run on that funny machine," Laddie said. "And maybe I can think up a riddle⁷ about it, after a while."
 
By th............