"What do you think causes the wind to blow so peculiarly here Tom?" went on Ned.
"Oh, it must be caused by high mountain ranges on either side, or the effects of heat and cold, the air being evaporated over a certain area because of great heat, say a volcano, or something like that; though I don't know that they have volcanoes here. That creates a vacuum, and other air rushes in to fill the vacant space. That's all wind is, anyhow, air rushing in to fill a vacuum, or low pressure zone, for you remember that nature abhors a vacuum."
It took nearly a week to assemble the Vulture, as Tom had named his latest craft, from the fact that it could hover in the air motionless, like that great bird. At last it was completed and then, weights being taken aboard to steady it, all was ready for the test. Tom would have liked to have taken all his passengers in the glider, for it would work better then, but the three Russians were timid, though they promised to get aboard after the trial.
The test came off early one morning, Tom, Ned and Mr. Damon being the only ones aboard. Bags of sand represented the others. The glider was wheeled to the edge of the wind zone and they took their places in the car. It was hard work, for the gale, that had never ceased blowing for
