"It was the great wind," explained Tom. "It blows only in a certain zone, like a draft down a chimney. It is like a cyclone, only that goes in a circle. This is a straight wind, but the path of it seems to be as sharply marked as a trail through the forest. I guess we're here all right. Does this location look familiar to you?" he asked of the Russian brothers.
"I can't say that it does," answered Ivan. "But then it was winter when we were here."
"And, another thing," put in Peter. "That wind zone is quite wide. The mine may be in the middle, or near the other edge."
"That's so," agreed Tom. "We'll soon see what we can do. Come on, Ned, let's get the air glider out and put her together. She'll have a test as is a test, now."
I shall not describe the tedious work of re-assembling Tom Swift's latest invention in the air craft line—his glider. Sufficient to say that it was taken out from where it had been stored in separate pieces on board the Falcon, and put together on the plain that marked the beginning of the wind zone.
It was a curious fact that twenty feet away from the path of the wind scarcely a breeze could be felt, while to advance a little way into it meant that one would at once be almost carried off his feet.
Tom tested the speed of it one day with a special anemometer, and found that only a few hundred feet inside the zone the wind blew nearly one hundred miles an hour.
"What is it like inside, I wonder?" asked Ned.
"It must be terrific," was his chum's opinion.
"Dare you risk it, Tom?"