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 then gradually come down, and when it is within
five or six feet of the ground the man must instantly strike the wings
downwards, and sit as far back as he can; he will by this means check
the projectile force, and cause the car to alight very gently with a
retrograde motion. The car, when up in the air, may be made to turn
to the right or to the left by forcing out one of the fins, having one
about eighteen inches long placed vertically on each side of the car for
that purpose, or perhaps merely by the man inclining the weight of his
body to one side.'

Having stated how the thing is to be done, Walker is careful to explain
that when it is done there will be in it some practical use, notably in
respect of the conveyance of mails and newspapers, or the saving of
life at sea, or for exploration, etc. It might even reduce the number of
horses kept by man for his use, by means of which a large amount of land
might be set free for the growth of food for human consumption.

At the end of his work Walker admits the idea of steam power for driving
a flying machine in place of simple human exertion, but he, like Cayley,
saw a drawback to this in the weight of the necessary engine. On the
whole, he concluded, navigation of the air by m