Upon the Blackboard was the illustration
you see in the frontispiece.
``I am the side view of a Surface,'' it said, mimicking
the tones of the lecturer. ``Flight is secured by driving me
through the air at an angle inclined to the direction of
motion.''
``Quite right,'' said the Angle. ``That's me, and I'm
the famous Angle of Incidence.''
``And,'' continued the Surface, ``my action is to deflect
the air downwards, and also, by fleeing from the air behind,
to create a semi-vacuum or rarefied area over most of the
top of my surface.''
``This is where I come in,'' a thick, gruff voice was
heard, and went on: ``I'm the Reaction. You can't have
action without me. I'm a very considerable force, and my
direction is at right-angles to you,'' and he looked heavily
at the Surface. ``Like this,'' said he, picking up the chalk
with his Lift, and drifting to the Blackboard.
``I act in the direction of the arrow R, that is, more or
less, for the direction varies somewhat with the Angle of
Incidence and the curvature of the Surface; and, strange
but true, I'm stronger on the top of the Surface than at
the bottom of it. The Wind Tunnel has proved that by
exhaustive research--and don't forget how quickly I can
grow! As the speed through the air increases my strength
increases more rapidly than you might think--approximately,
as the Square of the Speed; so you see that if the Speed of
the Surface through the air is, for instance, doubled, then
I am a good deal more than doubled.
Pages:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25