Thomas
Walker
(active early 1800s)
Practically
contemporary with Cayley was Thomas Walker, concerning whom little
is known save that he was a portrait painter of Hull, where
was published his pamphlet on The Art of Flying in 1810, a
second and amplified edition being produced, also in Hull,
in 1831. The pamphlet, which has been reproduced in extenso
in the Aeronautical Classics series published by the Royal
Aeronautical Society, displays a curious mixture of the true
scientific spirit and colossal conceit. Walker appears to
have been a man inclined to jump to conclusions, which
carried him up to the edge of discovery and left him
vacillating there.
Thomas Walker's Flying Machine of 1810
The study of the two
editions of his pamphlet side by side shows that their
author made considerable advances in the practicability of
his designs in the 21 intervening years, though the drawings
which accompany the text in both editions fail to show
anything really capable of flight. The great point about
Walker's work as a whole is its suggestiveness; he did not
hesitate to state that the 'art' of flying is as truly
mechanical as that of rowing a boat, and he had some
conception of the necessary mechanism, together with an
absolute conviction that he knew all there was to be known.
'Encouraged by the public,' he says, 'I would not abandon my
purpose of making still further exertions to advance and
complete an art, the discovery of the true principles
(the italics are Walker's own) of which, I trust, I can with
certainty affirm to be my own.'
The pamphlet begins with
Walker's admiration of the mechanism of flight as displayed
by birds.
'It is now almost twenty
years since I was first led to think, by the study of
birds and their means of flying, that if an artificial
machine were formed with wings in exact imitation of the
mechanism of one of those beautiful living machines, and
applied in the very same way upon the air, there could be
no doubt of its being made to fly, for it is an axiom in
philosophy that the same cause will ever produce the same
effect.'
With this he confesses his
inability to produce the said effect through lack of funds,
though he clothes this delicately in the phrase
'professional avocations and other circumstances.' Owing to
this inability he published his designs that others might
take advantage of them, prefacing his own researches with a
list of the very early pioneers, and giving special mention
to Friar Bacon, Bishop Wilkins, and the Portuguese friar, De
Guzman. But, although he seems to suggest that others should
avail themselves of his theoretical knowledge, there is a
curious incompleteness about the designs accompanying his
work, and about the work itself, which seems to suggest that
he had more knowledge to impart than he chose to make
public--or else that he came very near to complete solution
of the problem of flight, and stayed on the threshold
without knowing it.
After a dissertation upon
the history and strength of the condor, and on the
differences between the weights of birds, he says:
'The following
observations upon the wonderful difference in the weight
of some birds, with their apparent means of supporting it
in their flight, may tend to remove some prejudices
against my plan from the minds of some of my readers. The
weight of the humming-bird is one drachm, that of the
condor not less than four stone. Now, if we reduce four
stone into drachms we shall find the condor is 14,336
times as heavy as the humming-bird. What an amazing
disproportion of weight! Yet by the same mechanical use of
its wings the condor can overcome the specific gravity of
its body with as much ease as the little humming-bird. But
this is not all. We are informed that this enormous bird
possesses a power in its wings, so far exceeding what is
necessary for its own conveyance through the air, that it
can take up and fly away with a whole sheer in its talons,
with as much ease as an eagle would carry off, in the same
manner, a hare or a rabbit. This we may readily give
credit to, from the known fact of our little kestrel and
the sparrow-hawk frequently flying off with a partridge,
which is nearly three times the weight of these rapacious
little birds.'
After a few more
observations he arrives at the following conclusion:
'By attending to the
progressive increase in the weight of birds, from the
delicate little humming-bird up to the huge condor, we
clearly discover that the addition of a few ounces,
pounds, or stones, is no obstacle to the art of flying;
the specific weight of birds avails nothing, for by their
possessing wings large enough, and sufficient power to
work them, they can accomplish the means of flying equally
well upon all the various scales and dimensions which we
see in nature. Such being a fact, in the name of reason
and philosophy why shall not man, with a pair of
artificial wings, large enough, and with sufficient power
to strike them upon the air, be able to produce the same
effect?'
Walker asserted definitely
and with good ground that muscular effort applied without
mechanism is insufficient for human flight, but he states
that if an aeronautical boat were constructed so that a man
could sit in it in the same manner as when rowing, such a
man would be able to bring into play his whole bodily
strength for the purpose of flight, and at the same time
would be able to get an additional advantage by exerting his
strength upon a lever. At first he concluded there must be
expansion of wings large enough to resist in a sufficient
degree the specific gravity of whatever is attached to them,
but in the second edition of his work he altered this to
'expansion of flat passive surfaces large enough to reduce
the force of gravity so as to float the machine upon the air
with the man in it.' The second requisite is strength enough
to strike the wings with sufficient force to complete the
buoyancy and 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 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 means of engine power would be mostly confined to
the construction of navigable balloons.
As already noted, Walker's
work is not over practical, and the foregoing extract
includes the most practical part of it; the rest is a series
of dissertations on bird flight, in which, evidently, the
portrait painter's observations were far less thorough than
those of da Vinci or Borelli. Taken on the whole, Walker was
a man with a hobby; he devoted to it much time and thought,
but it remained a hobby, nevertheless. His observations have
proved useful enough to give him a place among the early
students of flight, but a great drawback to his work is the
lack of practical experiment, by means of which alone real
advance could be made; for, as Cayley admitted, theory and
practice are very widely separated in the study of aviation,
and the whole history of flight is a matter of unexpected
results arising from scarcely foreseen causes, together with
experiment as patient as daring.
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