Both boys saw it at the same time.
"A tornado!" cried Anton.
"Let's get to the cellar!" cried Ross, and started to run, but Anton grasped him by the shoulder.
"No," he said, "we're safe here; it'll pass to the east over the farm lands and won't hit anybody."
In a few seconds Ross saw that the crippled lad was right, and, themselves safe, the boys watched the passing of the tornado.
"It's going about thirty miles an hour," said Anton, figuring rapidly, "and it's all of fifteen miles away. There won't be much left of it by the time it passes here. We don't need to worry."
Reassured, Ross turned to his companion, and asked:
"What makes tornadoes, Anton?"
"A quick current of warm air going up in a thunderhead cloud," he said, "which takes a spinning motion from the general whirl of the cyclone to which it belongs. It has a whirling vortex, from the outside to the inside, and its speed gets higher toward the middle. The speed of the inside of a tornado has never been figured out, but it has been estimated at eight hundred miles an hour, or sixteen times as fast as a train."
"Eight hundred miles an hour!" Ross repeated. "But how did they find that out?"