surfaces must be perfectly equal in length and breadth and large
enough to cover a sufficient quantity of air to support the whole
weight as nearly in equilibrium as possible, thus we shall have a
great sustaining power in those passive surfaces and the active
wings will propel the car forward.'

A description of how to launch this car is subsequently given:
'It becomes necessary,' says the theorist, 'that I should give
directions how it may be launched upon the air, which may be done
by various means; perhaps the following method may be found to
answer as well as any: Fix a poll upright in the earth, about
twenty feet in height, with two open collars to admit another
poll to slide upwards through them; let there be a sliding
platform made fast upon the top of the sliding poll; place the
car with a man in it upon the platform, then raise the platform
to the height of about thirty feet by means of the sliding poll,
let the sliding poll and platform suddenly fall down, the car
will then be left upon the air, and by its pressing the air a
projectile force will instantly propel the car forward; the man
in the car must then strike the active wings briskly upon the
air, which will so increase the projectile force as to become
superior to the force of gravitation, and if he inclines his
weight a little backward, the projectile impulse will drive the
car forward in an ascending direction. When the car is brought to
a sufficient altitude to clear the tops of hills, trees,
buildings, etc., the man, by sitting a little forward on his
seat, will then bring the wings upon a horizontal plane, and by
continuing the action of the wings he will be impelled forward
in that direction. To descend, he must desist from striking the
wings, and hold them on a level with their joints; the car will