“What does he mean—­a wooden hill in the barn?” asked Mrs. Bunker.

“It was the treadmill,” explained Thomas Hardy.  “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 automobiles 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, trotting 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 riddle about it, after a while.”

By this time the rest of the little Bunkers had come out to the barn and, led by Tom, they went upstairs to see the treadmill.  It was a big machine, with wheels and rollers; and a wooden platform, made of cross sticks, so the feet of the horse would not slip, was what Russ had run on.  As he walked up a “wooden hill,” as he called it, the slats moved from under his feet, for this is what they were meant to do when the horse should walk on them.  And this moving platform of wood spun a wheel around, which, in its turn, would work a churn, a machine for threshing wheat or rye or do other work on the farm.

“But we haven’t used the treadmill for years,” said Grandma Bell.  “I forgot about its being in the barn.  Well, I’m glad no one was hurt.  But be careful after this.”

“I’d like to see it work,” remarked Rose, so Tom Hardy got on the wooden platform and walked up the little hill it made.  Then came the rumbling sound, and the faster Tom walked the faster the treadmill went around.