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?"

"Of course. The harder it blows the better the glider works. In fact I
can't make much speed in a hundred-mile wind for with us all on board
the craft will be heavy, and you must remember that I depend on the
wind alone to give me motion."

"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
an instant since they found its zone, was very strong. But the glider
remained motionless in it, for the wing