impossible, and I am sure the Designer will be quite
satisfied if you become the Most Efficient Compromise."

"Well, that sounds so common sense," sighed Efficiency, "I suppose it
must be true, and if the Designer is satisfied, that's all I really care
about. Now do let's get on with the job."

So the Chalk drew a nice long slim body to hold the Engine and the
tanks, etc., with room for the Pilot's and Passenger's seats, and placed
it exactly in the middle of the Biplane. And he was careful to make its
position such that the Centre of Gravity was a little in advance of the
Centre of Lift, so that when the Engine was not running and there was
consequently no Thrust, the Aeroplane should be "nose-heavy" just to the
right degree, and so take up a natural glide to Earth--and this was to
help the Pilot and relieve him of work and worry, should he find himself
in a fog or a cloud. And so that this tendency to glide downwards should
not be in evidence when the Engine was running and descent not desired,
the Thrust was placed a little below the Centre of Drift or Resistance.
In this way it would in a measure pull the nose of the Aeroplane up and
counterbalance the "nose-heavy" tendency.

And the Engine was so mounted that when the Propeller-Thrust was
horizontal, which is its most efficient position, the Angle of Incidence
and the Area of the surfaces were just sufficient to give a Lift a
little in excess of the Weight. And the Camber was such that, as far as
it was concerned, the Lift-Drift Ratio should be the best possible for
that Angle of Incidence. And a beautifully simple under-carriage was
added, the outstanding features of which were simplicity, strength,
light-weight, and minimum drift. And, last of all, there was the
Elevator, of which you will hear more by-and-by. And this is what it
looked like then:

And Efficiency, smiling, thought that it was not such a bad compromise
after all and that the Designer might well be satisfied.

"Now," said she, "there's just one or two points I'm a bit hazy about.
It appears that when the Propeller shaft is horizontal and so working
in its most efficient attitude, I shall have a Lift from the Surfaces
slightly in excess of the Weight. That means I shall ascend slightly,
at the same time making nearly maximum speed for the power and thrust.
Can't I do better than that?"

"Yes, indeed," spoke up the Propeller, "though it means that I must
assume a most undignified attitude, for