give a projectile motion to the machine. Given
these two requisites, Walker states definitely that flying must be
accomplished simply by muscular exertion. 'If we are secure of these two
requisites, and I am very confident we are, we may calculate upon the
success of flight with as much certainty as upon our walking.'

Walker appears to have gained some confidence from the experiments of a
certain M. Degen, a watchmaker of Vienna, who, according to the Monthly
Magazine of September, 1809, invented a machine by means of which a
person might raise himself into the air. The said machine, according to
the magazine, was formed of two parachutes which might be folded up or
extended at pleasure, while the person who worked them was placed in the
centre. This account, however, was rather misleading, for the magazine
carefully avoided mention of a balloon to which the inventor fixed his
wings or parachutes. Walker, knowing nothing of the balloon, concluded
that Degen actually raised himself in the air, though he is doubtful
of the assertion that Degen managed to fly in various directions,
especially against the wind.

Walker, after considering Degen and all his works, proceeds to detail
his own directions for the construction of a flying machine, these
being as follows: 'Make a car of as light material as possible, but
with sufficient strength to support a man in it; provide a pair of wings
about four feet each in length; let them be horizontally expanded and
fastened upon the top edge of each side of the car, with two joints
each, so as to admit of a vertical motion to the wings, which motion may
be effected by a man sitting and working an upright lever in the middle
of the car. Extend in the front of the car a flat surface of silk, which
must be stretched out and kept fixed in a passive state; there must
be the same fixed behind the car; these two 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