his weeks of
arduous labor pleased the leader of the Wolf patrol more than he
could express in words.

Bud was about the busiest boy any one had ever known. To run along
and keep, up with that hurrying model, hanging on to the long stout
cord, was no easy task. The rudder had certainly been fixed properly
to insure a circuit of the field; but as the ground was very rough in
places, Bud had great difficulty in keeping from falling many times.
This was partly on account of the fact that he had to fasten his eyes
on the scurrying monoplane model pretty much all the time, and could
therefore not pay much attention to where he was going, or see the
traps lying in the way of his feet.

He stuck to his task heroically, with grim determination to see it
through to the bitter end. Every once in a while he would give the
cord a savage jerk. In this way he managed to make the little flier
take sudden lurches; but in every instance the model instantly resumed
its upright position as soon as the pull was past. It reminded Hugh
of prank-loving swimmers attempting to sink a boat built with air
chambers, which would bob to the surface triumphantly every time.

So far as one could tell from watching these rather clumsy operations
on the part of the inventor, his apparatus for steadying an aeroplane
was surely showing signs of being a success. It consisted of a small
iron bar weighing an ounce or so, which was hung as a pendulum from
an arm projecting from under the operator's seat. This pendulum was
so delicately set that it seemed to respond to the slightest
deviation of the aeroplane from the horizontal.

As the excited inventor explained to his chums, after he had allowed
the craft to come to earth again, not without some little damage
which precluded another flight that day, it was a very simple thing
after all. If the craft was thrown from its balance in any way,
the movement of this pendulum would cause two little valves to open.
This would make the compression from the engine force a piston back
and forth, which communicated with the warping levers and
automatically accomplished what had up to that time, Bud went on to
say, been done by the hand of the busy aviator. Thus a mechanical
balancer had been arranged, so that the pilot need never bother
himself as to whether a stiff gale were blowing or not, since
practically nothing could upset his craft.

"It looks to me as if you had a good idea there, Bud," said Hugh