a sail of starched linen
a frame of reed
turned by men on the deck
A
screw
that
bites
the
air
the faster it turns, the harder it grips the air
Turn
it,
and
it
grips
air pushed down
pushed up
Air
goes
down,
it
goes
up
what four men could give
what lifting it would take
Why
it
never
flew
Leonardo's
aerial
screw