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. "But we're not going to get anything like that this time." As the boys were talking, the distant tornado suddenly raised itself from the ground and seemed to be drawn up in the clouds again. The danger from the funnel was over. A few minutes afterwards, there came a clap of thunder and the rain commenced to fall in torrents. It rained for less than a minute, however, then was followed by a few hailstones as large as walnuts. The hail stopped as suddenly as it had begun. Yet, though the funnel cloud had been withdrawn again into the sky, though the rain and hail had ceased, the two boys did not move from the doorway of the club-house. The sky was pressing down heavily and in the masses of clouds that seemed to be moving in every direction, the whitish luminous cloud and the greenish black cloud could both be traced. This was no puny battle of the elements, but a veritable war. Then, absolutely without warning, as suddenly as though some malevolent demon had picked them out for destruction, from the low-lying bank of clouds that was advancing, a long black swaying clutch thrust at them from the clouds. For a second or two the funnel swayed as though there were eyes in its tip and then snatched at the earth with a roar and crash like a thousand trains in collision. While one could count three, the lads watched, panic-stricken, then Anton shouted: "Run north-west, Ross! North-west!"