n't
there something about Stability and Control? Don't you think I ought to
have a glimmering of them too?"

"Well, I should smile," said a spruce Spar, who had come all the way
from America. "And that, as the Lecturer says, `will be the subject of
our next lecture,' so be here again to-morrow, and you will be glad to
hear that it will be distinctly more lively than the subject we have
covered to-day."

PART II. THE PRINCIPLES, HAVING SETTLED THEIR DIFFERENCES, FINISH THE
JOB

Another day had passed, and the Flight Folk had again gathered together
and were awaiting the arrival of Efficiency who, as usual, was rather
late in making an appearance.

The crowd was larger than ever, and among the newcomers some of the most
important were the three Stabilities, named Directional, Longitudinal,
and Lateral, with their assistants, the Rudder, Elevator, and Ailerons.
There was Centrifugal Force, too, who would not sit still and created a
most unfavourable impression, and Keel-Surface, the Dihedral Angle, and
several other lesser fry.

"Well," said Centrifugal Force, "I wish this Efficiency I've heard so
much about would get a move on. Sitting still doesn't agree with me
at all. Motion I believe in. There's nothing like motion--the more the
better."

"We are entirely opposed to that," objected the three Stabilities, all
in a breath. "Unless it's in a perfectly straight line or a perfect
circle. Nothing but perfectly straight lines or, upon occasion, perfect
circles satisfy us, and we are strongly suspicious of your tendencies."

"Well, we shall see what we shall see," said the Force darkly. "But who
in the name of blue sky is this?"

And in tripped Efficiency, in a beautifully "doped" dress of the latest
fashionable shade of khaki-coloured fabric, a perfectly stream-lined
bonnet, and a bewitching little Morane parasol,[4] smiling as
usual, and airily exclaiming, "I'm so sorry I'm late, but you see the
Designer's such a funny man. He objects to skin friction,[5] and
insisted upon me changing my fabric for one of a smoother surface, and
that delayed me. Dear me, there are a lot more of us to-day, aren't
there? I think I had better meet one at a time." And turning to
Directional Stability, she politely asked him what he preferred to do.

"My purpose in life, miss," said he, "is to keep the Aeroplane on its
course, and to achieve that there must be, in effect, more Keel-Surface
behind the Vertical Turning Axis than