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; “and unless somebody’s been ahead of you in the field, it ought to make you famous as an inventor.  Perhaps when you try it again to-morrow, after mending your planes, you’ll discover a few ways in which it can be improved.  Never believe anything is perfect the first time.  And now, shall we gather it up again and carry it to the cabin?”

“You’re awfully kind, Hugh!” declared the happy Bud, whose face was rosy from his recent tremendous exertions and from the glow of satisfied ambition.  “I am convinced that I haven’t been wasting my time, even if I’m only harrowing in a field some other fellow may have plowed before me.”

They managed to get the miniature aeroplane over to the shack, though it was no light burden, taken all in all.  Bud, however, was feeling so pleased that he could have done the work of an ox himself.  There is nothing like satisfaction to bring out unsuspected powers in a boy; and just then Bud believed he could have carried as great a load as any Turkish hamel or porter.

Leaving the queer looking contrivance outside the door, Bud hurried in as though something that he had suddenly thought of was bothering him.  A minute later he burst into view again, a row of wrinkles across his forehead and words of alarm sounding from his lips.