ion is how to keep a machine
from turning turtle, or turning over, when it strikes an unexpected
current, or 'air pocket' in the upper regions. Of course a birdman
may, by warping his wings, or changing the elevation of his rudder,
come out safely, but there is always a chance of danger or death.

"If there was some automatic arrangement by which the airship would
right itself, and take care of the unexpected tilting, there would be
practically no danger.

"I realized that as soon as I began making airships, and so I devised
what I call a gyroscope equilibrizer or stabilizer. A gyroscope, you
know, is a heavy wheel, spinning at enormous speed, on an anti-friction
axle. Its great speed tends to keep it in stable equilibrium, and, if
displaced by outside forces, it will return to its original position.

"You have probably seen toy ones; a heavy lead wheel inside a ring.
When the wheel is spinning that, and the ring in which it is contained,
may be placed in almost any position, on a very slender support and
they will remain stable, or at rest.

"So I put a gyroscope on my airship, and I found that it kept the
machine in a state of equilibrium no matter what position we were
forced to take by reason of adverse currents. Of course it was not an
entire success, but I was coming to that.

"In the biplane which was wrecked in the river I had my latest
gyroscope. It seemed to be perfect, and, with Jack and Harry, I had
made a number of beautiful flights. I even flew alone upside down, and
had no trouble.

"Before that I had made the acquaintance of Lieutenant Larson, who is
also an expert aviator. He worked for me before he went in the army.
He had his own ideas about equilibrium, and his plan, which he wanted
me to adopt, consists of tubes of mercury that can automatically be
tilted at different angles. I do not believe they will ever work, and
I told him so. I refused to use them, and he and I parted, not the
best of friends. He wanted his invention exploited, but I refused to
try it, as I thought it dangerous.

"When my gyroscope worked fairly well, I presume Lieutenant Larson was
professionally jealous. At any rate he, left me, and I am glad of it."

"But he was around our workshop just before we made this last flight!"
insisted Jack. "He came in pretending he had left some of his
important drawings behind when he went away, but I noticed that he hung
around the airship a good bit. I saw him looking at