The whole thing is nothing but a Compromise.'' And he
glared fixedly at poor Efficiency.

``Oh, dear! Oh, dear!'' she cried. ``I'm always getting
into trouble. What WILL the Designer say?''

``Never mind, my dear,'' said the Lift-Drift Ratio,
consolingly. ``You are improving rapidly, and quite useful
enough now to think of doing a job of work.''

``Well, that's good news,'' and Efficiency wiped her eyes
with her Fabric and became almost cheerful. ``Suppose
we think about finishing it now? There will have to be an
Engine and Propeller, won't there? And a body to fix
them in, and tanks for oil and petrol, and a tail, and,'' archly,
``one of those dashing young Pilots, what?''

``Well, we are getting within sight of those interesting
Factors,'' said the Lift-Drift Ratio, ``but first of all we
had better decide upon the Area of the Surfaces, their Angle
of Incidence and Camber. If we are to ascend as quickly
as possible the Aeroplane must be SLOW in order to secure
the best possible Lift-Drift Ratio, for the drift of the struts
wires, body, etc., increases approximately as the square
of the speed, but it carries with it no lift as it does in the
case of the Surface. The less speed then, the less such
drift, and the better the Aeroplane's proportion of lift to
drift; and, being slow, we shall require a LARGE SURFACE in
order to secure a large lift relative to the weight to be carried.
We shall also require a LARGE ANGLE OF INCIDENCE relative to