itish cloud of the north-west towering above the sinister black cloud
of the south-west. For a moment, almost as if they paused, a strip of
blue sky could be seen between them, then with a sudden rush, the two
collided. So solid seemed the masses of the clouds that both boys
started, expecting a clap of thunder. Yet never a flash of lightning
appeared nor was there any sound.

In the whirl of the two meeting clouds there was a minute of confusion,
and then, slowly, a long funnel, like a black finger, began to reach
towards the earth.

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?"

"Not by any instrument," said Anton; "there isn't anything made that a
tornado wouldn't level to the ground. But you can figure that from the
size and weight of objects lifted and from the effects of tornadoes.
Anyhow, the inside of a tornado is like a vacuum, the pressure is so
low.

"I remember reading in a tornado account of a storm in New England where
the funnel passed within twenty yards of a house. It was exactly as if a
house filled with air were suddenly plunged into a vacuum. All the
windows were blown out, the walls bulged, furniture flew out of the
windows and corks were drawn from empty bottles by the air inside trying
to get out to fill the vacuum in the tornado."

"That's a wonder," ejaculated Ross. "Bu