_The Kite.--Its construction.--The Tail.--An Author’s
meditations among the catacombs of Paternoster Row.--Works
in their winding sheets.--How Mr. Seymour strung puns as
he strung the Kite’s tail.--The Vicar’s dismay.--The
Weather, with the hopes and fears which it alternately
inspired.--Kites constructed in various shapes.--The
figure usually adopted to be preferred.--The flight of the
Kite.--A philosophical disquisition upon the forces by
which its ascent is accomplished.--The Tail.--A Discourse
on the theory of flying.--The structure and action of the
wings of birds.--A series of kites on one string.--A Kite
Carriage.--The Messenger.--The causes and velocity of wind
explained._
The children were summoned into the library, and informed by their
father that he was at leisure to explain the philosophy of the kite; a
subject with which Tom had repeatedly expressed some impatience to
become acquainted.
“It is a beautiful day,” exclaimed the boy joyously; “and there is such
a delightful breeze, that I should really call it a complete
_kite-day_.”
“Gently, my fine fellow,” replied Mr. Seymour: “the bird must be
fledged, ere it can fly. We have not, as yet, any kite: for you know
that the one you possess is shattered beyond the possibility of repair.”
“True, papa; but could not Robert just step into the village and buy
one? I saw several kites in the shop of Peg Robson yesterday.”
“I do not doubt it, my boy; but the kites which are to be found in the
toy-shop are made to sell, rather than to fly; and to _raise the wind_,
for the benefit of the vender, rather than to be raised _by it_, for
the amusement of the purchaser: we must, therefore, construct one for
ourselves; and see, I have, accordingly, prepared all the necessary
materials for the purpose. I have here, as you perceive, a straight
lath of deal, about three-quarters of an inch wide, and less than a
quarter of an inch thick, and about four feet in length; this is quite
ready for forming the standard, or _back-bone_ of the kite: and now for
the bow. The cooper has complied with my directions, and sent an unbent
hoop, as free as possible from knots; you observe that it is about the
same length as the lath, but it will be necessary to pare it down a
little at each end, in order to make it bend more readily to the
required shape.”
[Illustration: Diagram of a kite, labeled a through f.]
This having been accomplished, Mr. Seymour proceeded to form the
framework of the kite in the following manner. He first ascertained the
central point of the bow, by balancing it on his fore-finger; he then
affixed that point, by means of string, to the lath, at _c_, about an
inch and a half from its upper extremity; a notch was next cut in each
end of the hoop, or bow, _a d_; having fixed the string in the notch,
_a_, he drew it through another, _e_, previously cut in the bottom of
the lath, and carried it to the opposite end of the bow _d_; the
skeleton now presented the usual form, of the kite. The next point,
therefore, was to ascertain whether the two sides of the bow were in
equilibrio, which he determined by balancing the lath on the finger,
and observing whether it remained horizontal, or dipped on either side.
This adjustment having been accomplished, Mr. Seymour next continued
the string from _d_ across the skeleton to the opposite notch _a_,
giving it one turn round the lath in its way; from _a_ it was carried
to _f_, and wound round the top of the lath, and then again fastened at
_d_; from _d_ it was extended rather more than midway down the lath,
and having been secured at _b_, was finally carried to, and secured in
the notch _a_. The framework was now pronounced by Mr. Seymour to be
complete.[41]
The next part of the process was to cover it with paper. Mr. Seymour
observed, that the best kind which could be employed for this purpose
was that known amongst stationers by the name of _fan paper_, so called
from its being manufactured for the use of the fanmaker; its merits, he
said, depended upon the size of its sheets, as well as upon the
thinness and firmness of its texture: this, however was not at hand; he
was therefore obliged to rest satisfied with its best substitute, viz.
folio sheets of large thin post.
The party now went “ding-dong” to work; paper, paste, and scissors were
immediately put in requisition. Sheets of paper were laid smooth on the
table, and so arranged that each sheet overlapped its neighbour about
half an inch. The skeleton of the kite was then placed upon them, and
the paper was cut to its figure; a margin, of about three-quarters of
an inch, having been left around it, except over the bow, where the
margin was extended to an inch in width: this arrangement was for the
purpose of allowing the paper to turn over the framework, when pasted
to it. This part of the work having been completed, and a sufficient
time allowed for the drying of the paste, Mr. Seymour proceeded to fix
the string, usually termed the _belly-band_: for this purpose two holes
were drilled through the lath, at equal distances from its edges; the
upper one about a fifth part of the length of the kite from the top,
the lower hole rather more than the same distance above its extremity.
The last, and by far the most important point, was to make the loop in
the _belly-band_. If the kite be accurately constructed, its proper
place may be easily found by extending the band, right or left, on the
surface of the kite, and then marking the string at a point which lies
in a line drawn from one end of the bow to the other; the loop must be
made a little above such a point. If the kite be now suspended by this
loop, the two ends of the bow ought to preserve a balance, and the
lower extremity should dip below the upper part of the kite.
As Louisa observed the extreme care with which her father adjusted this
part of the machine, she enquired into its use.
“I was myself about to put the same question,” said her mother; “for
its adjustment would appear to require as much accuracy as that of the
sash of a girl of sixteen.”
Mr. Seymour informed them, they would hereafter find that the steady
ascent of the kite into the air entirely depended upon such accuracy.
“Have you not seen, Tom,” asked he, “a kite rise sideways, or _plunge_,
as it is called?”
Tom said he had often experienced that difficulty at school, but that
he had attributed it to some defect in the tail.
“An error in the construction of the tail may, certainly, be
occasionally the cause of such an accident, but it is more generally
referable to an improper position of the loop: if the kite _plunges_,
you may conclude that this loop is placed too high; and should it whirl
round in the air, you may infer that it is too low.”
During this conversation Mr. Twaddleton entered the apartment; Tom was
anxious to show him his newly-constructed kite, and, while the party
were asking him numerous questions, Mr. Seymour observed, that the
vicar would be more profitably employed in making _bobs_ for the string
of the tail, than in finding answers for their string of questions.
Mrs. Seymour, and her daughters, with Tom and the vicar, were,
accordingly, placed round the table, for the purpose of carrying this
project into effect, by a suitable division of labour. It was arranged
that Mrs. Seymour should cut the paper, the vicar fold it, and Mr.
Seymour tie it on the string.
“How long ought the tail to be?” asked Tom.
“And of what shape should the papers be cut?” enquired Louisa.
“And at what distances are they to be placed from each other on the
string?” said Mrs. Seymour.
“I will answer all your queries,” replied the father, “by giving you a
dissertation upon this part of our machine.”
“We shall now have an harangue,” exclaimed the vicar, “as long as the
tail itself; but pray proceed.”
“The tail should never be less than twelve, and should it even amount
to twenty times the length of the kite, its appearance in the air will
be more graceful; this, however, must be regulated by the weight of the
string, and by the length and thickness of the pieces of paper of which
the tail is composed. The length of each ought to be about three inches
and a quarter, and an inch and a half in breadth, and it should be
folded four times longitudinally; each of these _bobs_, as they are
called, must be placed at regular intervals of three inches.”
“And with respect to the size of the wings?” asked the vicar.
“I should not recommend any wings; if the kite be well made, there
cannot be any advantage from such appendages. Having now answered your
several questions, let us proceed with our work.”
“But where is the paper?” asked Mrs. Seymour.
“Apropos,” answered her husband; “the box in which the London toys were
packed contains a quantity that will answer our purpose.”
The box was accordingly placed on the table.
“Why, what a most extraordinary miscellany!” cried the vicar; “the army
of Mithridates could not have consisted of a more incongruous mixture.
I perceive,” added he, as his enquiring eyes glanced from sheet to
sheet, “we have here a fragment of almost every description of literary
and scientific work.”
“The market,” observed Mr. Seymour, “is supplied with waste paper from
the catacombs of Paternoster Row, which may be truly said to ‘level all
distinctions.’ Without intending any offence by a pun, my good vicar,
what a _tale_ will this box unfold! I never open a magazine of this
waste paper, without feeling a deep sympathy for the melancholy fate of
authors: to see the strange transmigrations, and vile purposes, to
which their works are destined, is really heart-rending. That the
_lights_ of science should be consigned to the tallow-chandler! the
works of the moralist, so well calculated to _purify_ the world, to the
soap-seller! that such a book as ‘Laennec on the _Chest_,’ with Dr.
Forbes’s valuable _Cases_ in the bargain, should be _packed_ off to the
_trunk_-maker! are events which cannot fail to furnish food for
melancholy reflection. Nay, more, I have myself (can you believe it,
Mr. Twaddleton?) actually received a quantity of _ureic_ acid in a
Review of Dr. Thomson’s Chemistry! and I only yesterday learned, with
horror, that a piece of fat bacon was positively wrapped up in a page
of ‘Paris on Diet;’ while a Cheshire cheese came encased in Kitchener’s
‘Chart of the Moon.’”
“Oh, shameful! shameful!!” exclaimed the vicar: “but I can assure you,
that this unfeeling conduct of the publisher had not escaped my notice
and indignation; for I lately received a work against the slave-trade,
in the fragment of a tract on ‘the Progress of Cant;’ and a Copy of
Irving’s Orations, in an act of ‘Much Ado about Nothing;’ and what was
still worse,” continued the reverend divine, “a little work on the art
of Prognosticating the Weather, was forwarded to me in a chapter of
_Daniel’s_ Prophecies.”
“But let us quit these melancholy reflections for the present, and
proceed with our occupation.”
“If you compose the tail of your kite with these papers,” said the
vicar, “it will certainly vie with that of Scriblerus himself; you will
have a knot of divinity,--a knot of physic,--a knot of logic,--a knot
of philosophy,--a knot of poetry,--and a knot of history.”
“Never mind, my dear sir; I wager an edition of Virgil, that I shall be
able to discover in each page, with which you may present me, some
apposite allusion to the _tail_, of which it is to form a part.”
“Apposite allusion! impossible; as well might you attempt to connect
the scattered leaves of the Sibyl: for example, here is an Epitome of
the Roman History.”
“Very well,” said Mr. Seymour, “and pray is not that cur_tail_?”
The vicar dropped the paper in dismay; the treacherous design of his
friend now, for the first time, flashed across his brain with a painful
conviction, and he hastily retreated to a distant corner of the
library, or “_turned tail_,” as Mr. Seymour jocosely expressed it, in
order that he might find shelter from the pelting of a pitiless storm
of puns, which he saw, too clearly, was about to burst on his devoted
head.
On the vicar’s retiring from the table, Mrs. Seymour approached the
fatal box, observing, “that it was now her turn to explore the
Sibylline cave.”
“Here,” said she, “is a list of the prices of some newly published
works.”
“That,” replied her husband, as he cast a sly glance at the vicar, “is
re_tail_: pray, proceed.”
“We have next, I perceive, a prospectus for publishing all the speeches
in the late parliament.”
“That is de_tail_.”
Here a deep groan from Mr. Twaddleton arrested the progress of the
proceedings, and threw the whole party into a fit of laughter. As soon
as tranquillity was restored, Mrs. Seymour again dipped her hand into
the box, and drew forth the fragments of a work on Real Property.
“That,” said Mr. Seymour, “is en_tail_; pray, _cut it off_, and give it
to me.”
“We have here,” continued the lady, “the Memoirs of an Italian Bandit.”
“Then prepare him for his fate; I have a noose quite ready for his
reception.”
“Here is a poem, entitled Waterloo.”
“I will patronise it,” said her husband; “and I warrant you that, under
my auspices, the muse will soar to a greater height than she ever could
otherwise have attained.”
“We have here, I declare, a part of * * * * [sic] pamphlet.”
“Then I have lost my wager,” exclaimed Mr. Seymour, “for I defy the
power of man to make either head or _tail_ of it.”
Thus did Mr. and Mrs. Seymour proceed; the one cutting paper, the other
cutting jokes; nor did the former cease stringing puns, until he had
finished stringing the tail.
“I must now conclude by making a knot that shall not be in danger of
becoming untied in the breeze,” said Mr. Seymour: “but stop, stop one
moment! I still require one more piece of paper to complete my task,
and let it be double.”
“Here then is a piece of paper, which, from its texture, appears to be
well adapted to your purpose. Let me see, what is it? I declare it is
the titlepage of an Essay on Matrimony.”
“Capital!” cried her husband; “a strange coincidence, truly; you have,
indeed, furnished me with a knot that cannot be easily untied, however
stiff may be the breeze; hand it over to me, for it will afford a very
legitimate finish, and is generally the conclusion of every _tale_: but
where is the vicar? What, ho! Mr. Twaddleton.”
The reverend gentleman had so contrived to conceal his person in the
corner of the room, behind a large folio which he had placed on a desk
before him, that several moments elapsed before he was discovered; at
length, however, a long-drawn sigh betrayed him in his retreat.
“Upon my word,” exclaimed he, as he pushed aside the huge folio, “your
volatility, Mr. Seymour, is wholly inconsistent with the gravity of a
scientific instructor.”
“But, at present,” replied Mr. Seymour, “I am the manufacturer of a
kite’s tail; and, surely, upon such an occasion, _flightiness_ ought
not to be urged to my disparagement.”
The party, shortly after this discussion, separated: Mr. Seymour
retired to his own room; the vicar proceeded to the church to bury a
patient of Doseall’s; and the children ran into the garden to enjoy
their rural sports.
On the following day, before the wings of the lark had brushed away the
morning dew, Tom and his sisters, buoyant with expectation, had
descended into the garden, in order to ascertain the state of the
weather and the direction of the wind; but the sky was sullen and calm,
not a breath disturbed the susceptible leaves of the aspen; all was
repose--“a dread repose.”
“No kite-day this,” sighed Tom, with a countenance as lowering as the
morning clouds.
“Have patience,” said Louisa; “the wind may yet rise, it is only just
six o’clock.”
Thus did the minds of the children continue to hover between hope and
despair, until after breakfast, when they determined to seek the
gardener, and hold a grave consultation with that acknowledged judge of
the elements; he told them that showers might be expected, but he
thought it probable that the wind might rise after mid-day. “I will,
however,” said he, “consult my oracles;(33) after which, I shall be
able to give you a satisfactory opinion.” So saying, he left them; and,
on his return, observed that “as the _Siberian sow-thistle_ had closed
itself the preceding evening, and the _African marigold_ continued shut
after seven o’clock in the morning, he had thought there would be rain;
but,” he added, “that upon inspecting the _poor-man’s weatherglass_,
the _Anagallis arvensis_, or _red pimpernel_, two hours ago, he had
found it open, from which he concluded that the day would have been
fine.”
“There, Louisa; it will be a fine day, after all,” exclaimed her
delighted brother.
“No, indeed,” continued the gardener; “on returning just now to the
flower, which never deceives us, I found it had closed itself, so that
rain is inevitable.”
Nor was this opinion erroneous; for before the brother and sister could
reach the lodge, the heavy clouds began to discharge their watery
burthen, and the rain continued in one incessant shower for more than
two hours; it then gradually abated, and the children, who had been
anxiously watching it at the library window, were suddenly relieved
from their anxiety by the appearance of the vicar, whom they espied
slowly winding his way through the dripping shrubbery.
“‘Heu! quianam tanti cinxerunt æthera nimbi?’
as Virgil has it,” exclaimed the vicar, as he approached the portico,
where Mr. Seymour and his family had assembled to salute him.
“We are under the influence of St. Swithin, vicar,” said Mrs. Seymour,
“and I fear there is but slender hope of its becoming fair.”
“Psha! who cares for St. Swithin?(34) My barometer is rising rapidly,
and I place more confidence in that classical deity, Mercury, than in a
saint of so very questionable a character.”
At this moment, Phœbus, as if delighted by the compliment thus bestowed
upon his heathen brother, cast a sly glance from behind a dark cloud,
and illumined the spot upon which the vicar was standing. In short,
after the lapse of half an hour, the sun broke through the gloom, and a
brisk gale followed; the countenances of the children sympathised with
the face of the heavens, and the expression of hope lighted them up, in
proportion as the sun illumined the departing clouds with its radiance.
“It is now quite fair, papa,” cried Tom, in a voice of triumph, “and
there is a most delightful wind; shall we not proceed at once to the
common?”
“Presently,” answered his father: “the ground is yet extremely wet.”
In the course of an hour this objection had been removed, and the party
prepared to set off on their kite-flying expedition.
“Bring me the kite, and let me sling it properly over Tom’s shoulder,”
said Mr. Seymour.
“I will carry the string,” exclaimed Louisa; “how nicely it is wound
round the stick.”
As the party walked forwards, the vicar asked Tom whether he knew from
whence the name of the _kite_ originated.
“A kite is a bird of prey,” answered the boy, “which soars a great
height; and from remaining stationary in the air, was, I suppose,
thought to resemble the paper kite.”
“That is a very good explanation,” said the vicar; “or it may, perhaps,
have derived its name from the circumstance of its having been
originally constructed in the shape of a bird of this description. In
China the flying of kites is much more practised than in this country;
and I understand that their shape is always that of some bird.”
“In the London toy-shops you may constantly meet with them in such
forms, as well as in many other fantastic shapes,” observed Mr.
Seymour; “and,” continued he, “I remember to have seen, some years ago,
a kite which resembled a man. It was made of linen cloth, cut, and
painted for the purpose, and stretched on a light frame, so constructed
as to resemble the outline of the human figure. It stood upright, and
was dressed in a sort of jacket. Its arms were disposed like handles on
each side of its body, and its head being covered with a cap,
terminating in an angle, favoured the ascent of the machine, which was
twelve feet in height; but to render it easier to be transported, it
could be folded double, by means of hinges adapted to the frame. The
person who directed this kind of kite was able to raise it, though the
weather was calm, to the height of nearly five hundred feet; and, when
once raised, he maintained it in the air by giving only a slight motion
to the string. The figure, by these means, acquired a kind of
libration, like that of a man skaiting on the ice. The illusion,
occasioned by this spectacle, did not fail, as you may readily suppose,
to attract a great number of spectators.”
“I believe, however,” observed the vicar, “that the figure commonly
adopted, is the one best calculated for the purpose.”
“Undoubtedly,” replied Mr. Seymour, “and for obvious reasons; the
curvature of the bow enables it to escape the resistance of the air, as
it rises; which, after having struck it, slides off, just as the
current is more effectually turned aside by the gently curved prow,
than by that which has a sharp outline; for the same reason, the mast
of a ship, though it has a conical shape, is more easily drawn through
the water with its broad, than with its narrow end, foremost; for
although the primary obstruction is, no doubt, greater in the former
case, yet the water heaped, as it were, on the front, is made to stream
off with a slight divergency, and therefore does not hang on the sides
of the mast, as it would in the latter case. This shape of the kite,
moreover, presents the largest surface at the point upon which the wind
can act with the greatest effect, while the whole is lightened by the
removal of parts that would obstruct its action. The tail has also a
greater control over a figure of such a description.”
Mr. Seymour asked the vicar, “whether he could explain the origin of
the French term for the kite, viz. _cerf volant_, or flying stag; I
never can believe,” continued he, “that the kite could ever have been
constructed in the shape of that animal.”
“I am unable to clear up the difficulty,” replied the vicar; “and yet I
have taken some pains upon the subject. The earliest notice of the
kite, which I have been able to discover, is in a short English and
French Dictionary, by Miege, which was published in the year 1690, and
it is there described under the name of _cerf volant_.”
“I wonder,” cried Tom, “who invented the kite?”
“In, that, again,” answered Mr. Twaddleton, “I am unable to furnish you
with any satisfactory information. The pastime appears to be of very
ancient date in China, and was, probably, first imported into Europe
from that country.”
“At what period, do you suppose?”
“Strutt, who was very assiduous and correct in all his antiquarian
researches, was of opinion that its introduction into England could not
be dated farther back than a hundred and fifty years.”
The party had, by this time, reached Overton heath; the weather was
favourable; and the kite impatiently fluttered in the breeze, while Tom
was eagerly engaged in unwinding its streaming tail, and preparing the
paper machine for ascent.
“Is the string fixed to the belly-band?” asked Mr. Seymour.
“All is ready,” replied the vicar; “and I will hold it up, while Tom
runs with it against the wind. Had King Eric set his cap for us, we
could not have had a more favourable breeze.”
“There is not the least occasion to raise the kite from the ground,”
observed Mr. Seymour; “let its point rest on the grass, and place its
tail in a straight line in front of it; I warrant you it will rise, as
soon as Tom begins to run.”
Tom immediately set off, and the kite rose majestically into the air.
“Give it string--give it string--gently, gently--now stop; there is no
occasion for your running any farther but let out the cord, as long as
the kite carries it off vigorously, and keeps it fully stretched; but
wind it up the moment its tension is relaxed.”
“It is rising very fast,” cried the breathless boy, “but the string
burns my hand as it passes through it; I shall not be able to endure
the heat.”
“Be patient, and let it pass more slowly; put on your glove,” said his
father.
“Ay, ay; put on your glove,” repeated the vicar; “even Xenophon
himself, who declaimed so warmly against the effeminacy of the
Persians, for wearing gloves, would scarcely have refused his consent
to their use on such an occasion.”
“What is it that produces so much heat?” enquired Louisa.
“The friction of the string,” replied her father.
“Do you not know that carriages frequently catch fire from the friction
of their wheels, unless it be prevented by the application of grease?”
“Yes,” said Tom; “and I have heard that the natives of some countries
kindle their fires by rubbing pieces of wood together.”
“The original inhabitants of the new world,” observed his father,
“throughout the whole extent from Patagonia to Greenland, procured fire
by rubbing pieces of hard and dry wood against each other, until they
emitted sparks, or burst into flame; some of the people to the north of
California produced the same effect by inserting a kind of pivot in the
hole of a very thick plank, and causing it to revolve with extreme
rapidity: the same principle will explain how immense forests can have
been consumed; for it is evident, that the violent friction of the
branches against each other, from the agitation of the wind, would be
fully adequate to the production of such an effect.”
“You have also an excellent example of the effect of friction in
producing heat,” said the vicar, “in the history of the whale fishery;
for, in harpooning the fish, unless the sailors observe the greatest
caution in letting out the rope, its friction upon the side of their
boat will be sure to set it on fire.”
“And how do they manage it?” asked Louisa.
“As soon as the whale dives,(35) after having been wounded, it draws
out the line or cord of the harpoon, which is coiled up in the boat,
with very considerable velocity. In order, therefore, to prevent any
accident from the violence of this motion, one man is stationed with an
axe to cut it asunder, if it should become entangled; while another,
with a mop, is constantly cooling with water the channel through which
it passes.”
“The kite is now at a considerable height,” observed Tom; “but look at
the string, how bent it is! I have repeatedly endeavoured to pull it
straight, but without success.”
“How could you have expected to succeed in the attempt? Consider the
weight of such a long line of string.”
“Then it is not the pressure of the atmosphere which gives it that
curved form?”
“Assuredly not: have you so soon forgotten that the air presses equally
in all directions, and would therefore tend to straighten, as much as
to give a curved direction to the string? But, as you now appear to
have let out the whole of your string, suppose you allow the kite to
enjoy its airing, while we proceed to consider the philosophy of its
ascent, and the nature and direction of those forces by which it is
effected.”
“The kite pulls so amazingly hard,” cried Tom, “that unless I fix the
string securely around the tree, we shall run the chance of losing it.”
“I am well aware of the force it exerts,” replied his father. “Dr.
Franklin has said, that, with a good kite, a man unable to swim might
be sustained in the water, so as to pass from Dover to Calais; but I
agree with him in thinking, that a packet would be a much safer, as
well as a pleasanter mode of conveyance.”
“Now, then, for your explanation of the kite’s ascent. Unless I am
mistaken, you will find the subject much more complicated than you
imagine,” said the vicar.
“Not at all; Tom, who, I trust, has a perfect acquaintance with the
composition and resolution of forces, will very readily understand the
explanation I propose to offer. I admit, however, that there are some
few points in the enquiry, which cannot be successfully treated without
a knowledge of the higher branches of the mathematics; but I shall, of
course, avoid all such difficulties.[42] Can you tell me, Tom, what
advantage is gained by your running with the kite?” asked Mr. Seymour.
“I suppose that you thus obtain more force from the wind.”
“Certainly: action and reaction are equal. By running, therefore, with
your kite against the wind, you strike the air, and thus produce a
reaction, which is equal to the force of the blow given to it. When the
wind is high, and its action is not intercepted by surrounding objects,
there cannot exist any necessity for such an expedient.”
“The principle is the same as that which enables the bird to rise into
the air by flapping its wings,” observed the vicar.
“Unquestionably,” replied Mr. Seymour.
“Does the kite, then, rise in the air, from the same causes that enable
a bird to fly?” asked Tom.
“We are not, at present, considering the ascent of the kite, but the
advantage which is obtained by running with it: this latter, as the
vicar has properly observed, undoubtedly depends upon the same
principle as that which enables the bird to rise, by the motion of its
wings, and which constitutes the third law of motion,[43] viz. that
_action and reaction are equal_; that is to say, whenever one body
exerts a force upon another, the second body opposes the first, with
equal force, in an opposite direction. If, then, the bird strikes the
air below it with a force which is equal to its weight, then must there
be a reaction of the air, upwards, exactly equal to it; and the bird,
being acted upon by two equal forces, in opposite directions, will,
necessarily, rest between them.”
“That is clear enough; but the bird _rises_,” answered Tom.
“Because the force of the stroke is _greater_ than the weight of the
bird, and it therefore rises with the _difference_ of these two forces;
were the stroke _less_ than its weight, then would it sink with the
difference. Suppose, for example, a bird weighs _twelve_ ounces, and it
strikes the air with a force equal to _sixteen_, is it not clear that
it must rise with a force equal to _four_? and is it not evident that,
if it strikes the air with a force equal only to _eight_, that it must
sink with a force equal to _four_?”
“So far I understand it perfectly; but I was thinking that, as the wing
flaps up and down, what was gained by striking the air downwards must
be counterbalanced when the bird raised her wing again, and thus struck
the air in the contrary direction,” observed Tom.
“I give you no small degree of credit for that remark,” said his
father; “for it is undoubtedly true that, if the flapping of the wings
in flight were no more than the motion of the same surface upwards and
downwards, the bird must lose as much by one motion as she could gain
by the other; the skylark could never ascend by such an action, for, as
you have so justly remarked, although the stroke upon the air by the
under side of her wing would carry her up, the stroke from the upper
side, when she raised her wing again, would bring her down; but, if you
will attentively examine the structure of the wing, you will at once
perceive, from its external convexity, the disposition, and more
particularly the overlapping of its larger feathers, that when the wing
is drawn up, its surface is contracted, and when let down fully
expanded--or, in other words, that the feathers strike the air
downwards with their flat side, but rise from the stroke slantwise,
just as the rower in a boat, after having given the stroke, turns his
oar so as only to present its edge, an operation which is termed
_feathering_, from its resemblance to this very action of the wing in
flight.”
“It appears to me that flying is an easy process,” said Tom; “could we
not contrive some sort of flapper, by which we might be able to rise
into the air?”
“Your opinion, my dear boy, is by no means singular; hundreds have
entertained the same belief before you; and so confident was the famous
Bishop Wilkins, that he declared it to be his conviction, that, in
future ages, it will be as usual to hear a man call for his wings, as
it is now to call for his boots.”
“Yes,” said the vicar; “and if my memory is correct, William of
Malmesbury, in his account of the Conquest of England by the Normans,
mentions a Benedictine monk, by the name of Elmer, who having affixed
wings to his hands and feet, ascended a lofty tower whence he took his
flight, but he fell to the ground and broke both his legs.”
“I do not see the difficulty,” exclaimed Tom.
“The weight of our bodies is so great, that we have not sufficient
muscular strength to impart a blow to the air that shall be equal to
it. Now are you satisfied?” said his father.
“I am perfectly satisfied, if that be the case, that we can never hope
to fly.”
“The principle, however, which I have just explained,” observed Mr.
Seymour, “although it will fail us in our attempts to construct wings,
is nevertheless extensively applicable in mechanics. A vane or fly, for
instance, by resisting the air as it spins round, becomes the regulator
of machinery. The intervals between the strokes on the bell of a clock
are thus regulated, and the fly, on this occasion, is so contrived that
this interval may be altered, or the clock made to strike faster or
slower, by presenting the arms of it more or less obliquely to the
direction in which they move. The same kind of fly is the regulator
used in musical boxes, as I will presently show you, and indeed in
almost all mechanical toys. Let us now return to the subject of the
kite; for, as yet, we have merely considered the effect of increasing
the wind upon its surface; we have next to enquire how the wind
operates in raising it into the air.--Do you not remember, when I
adjusted the noose in the belly-band, I stated that much depended upon
this part of the apparatus? You will, at once, perceive that it will
influence the angle which the kite forms with the earth, and I am about
to prove to you, that the theory of the kite’s ascent is materially
connected with the value of this angle; but, in order to render my
explanation intelligible, I have prepared a diagram, to which I am
desirous of directing your attention.
[Illustration: Diagram of a kite labeled with A, B, O, S, T, W, and Y.]
“The kite here appears in the act of rising from the ground; the line W
will represent the direction of the wind blowing upon it, all the
currents of which we will suppose united in one; it is evident, from
what has been already stated, that as it falls upon an oblique surface,
it will be resolved into two forces, viz. into one parallel with it,
and into another perpendicular to that surface; of which the force
represented by the line Y will alone produce any effect, carrying the
kite along the line O A, or in a direction parallel to itself; and you
must have observed that this was the direction in which the kite was
impelled, when you suffered it to rise, without checking its progress
by the string.”
“I remember that well,” said Tom; “and I also observed that, when I
pulled my string, the kite immediately rose more perpendicularly.”
“To be sure it did; because, by that operation, you called a new force
into action; which I have represented in the diagram by the line S T.
The kite was therefore under the influence of the two forces O A and
S T, and, since these are in the direction of the two sides of a
parallelogram, it would not obey either, but ascend through O B, its
diagonal.”
“Notwithstanding Mr. Twaddleton’s doubts upon the subject,” said Tom,
“I am sure that I perfectly understand your explanation; and I think I
may also answer for my sister: but you have not yet told us any thing
about the tail; I suppose, however, that it acts like the rudder of a
ship, or the tail of a bird.”
“Before I answer that question, let me inform you how the tail of a
bird differs, in its action and uses, from the rudder of a ship. In the
first place, the rudder is so fixed that it can but move in one
horizontal plane, and can therefore only turn the vessel to the right
or left, which, indeed, is all that is required;(36) but the tail of
the bird, in addition to this motion, can be placed in a diagonal
direction, and when expanded will offer a considerable surface to the
air, so as to fulfil some of the offices of a third wing. Have you
never watched the manœuvres of the rook, as he gambols through the air?
After flying in the ordinary way, you will observe his wings at rest,
and that he glides along apparently without the least exertion in his
descent. In this case, his expanded wings act as a parachute; then,
again, you will observe him wheeling round, a manœuvre which is partly
produced by the oblique position of his tail, and which is readily
explained upon the principle of the resolution of forces I have just
described with reference to the action of the wind upon the surface of
the kite.(37) I ought also to state, that the tail serves to poise the
body of the bird.”
“Does the bird, then, never use its wings for the purpose of directing
its course?” asked Louisa.
“Undoubtedly it does,” answered her father; “the tail is only to be
considered as a supplementary organ: it is by means of the wings that
it generally directs its course, for it is evident, that it can easily
turn, either to the right or left, by flapping the opposite wing with
increased force, just as a boat is turned about to the right, by a
brisk application of the left oar. In like manner the irregular flight
of the butterfly, now up and now down, now to the right and now to the
left, is no doubt effected by the wings striking the air one after the
other, or perhaps with an alternate and unequal force. The object of
such an action is obviously to baffle the pursuit of birds which fly in
a right line, whereas you see the butterfly does just the contrary.”(38)
“How very wonderful,” said Louisa, “is the action of the wings of
insects. I have often watched them during their flight, and their
rapidity is such as to surpass the power of vision.”
“I shall have occasion to advert to that subject hereafter,” said Mr.
Seymour; “at present, I shall only observe, that a gnat’s wing, in its
ordinary flight, beats many hundred times in a second.”
“But you have not yet answered Tom’s question,” said the vicar. “Of
what use is the tail of the kite? Does it assist its ascent, or is it
merely an appendage of ornament?”
“In the first place, it keeps the head of the kite to the wind; and in
the next, it lowers its centre of gravity, and throws it towards its
extremity, which not only prevents the chance of the machine being
upset in the air, but so poises and regulates the position of the kite
as to maintain the angle which it is necessary for the string to make
with the surface.”
Mr. Twaddleton here enquired what might be the most advantageous angle
for the kite to form with the horizon, in order that the paper machine
should rise to the greatest altitude.
“If the wind be horizontal,” answered Mr. Seymour, “it is evident that
the inclination of the kite’s surface ought to be the same as that
which the rudder of a ship should make with the keel, in order that the
vessel may be turned with the greatest facility; supposing the currents
of water, which impel it, to have a direction parallel to the keel.”
“And what ought that angle to be?” enquired the vicar.
“_Fifty-four_ degrees, and _forty-four_ minutes,” replied Mr. Seymour;
“and let me here remark,” continued he, “as we have already considered
the philosophy of the flight of a bird, that its pinions are so set
upon the body as to bring down the wings in an _oblique_ direction
towards the tail; so that in their action upon the air, we have the
same resolution of forces as in that of the wind upon the surface of
the kite, by which the body of the bird is not only supported, or
raised perpendicularly, but carried forward.”(39)
Tom here interrupted the dialogue, by expressing a regret that he
should have been provided with so small a quantity of cord.
“I do not believe, my dear boy, that any advantage could be gained by
an additional quantity of string,” said his father.
“Is there, then, any reason why the kite should not ascend, even above
the clouds, provided that my string were sufficiently long and strong?”
“Yes; indeed is there a most unanswerable reason. Remember that the
kite is made to rise by the operation of two forces; the one afforded
by the wind, the other by the action of the string; now it is quite
evident that, when the weight of the string, added to that of the kite
itself, becomes equal to the force of the wind, acting upon the surface
of the machine, a general balance, or equilibrium, of forces will be
established, and the kite can no longer continue to ascend.”
“Will it, then, remain stationary under these circumstances?” asked
Louisa.
“It must do so, unless the force of the wind should abate; for it is a
proposition in mechanics, which I shall hereafter endeavour to
demonstrate(40), that, if a body be acted upon by three forces, which
are proportional to, and in the direction of, the three sides of a
triangle, it will be kept at rest. The kite is exactly in this
predicament, for its weight, the force of the wind, and the action of
the string, fulfil these conditions, and consequently keep the kite
stationary.”
“Then I must give up my intention of trying to raise the kite above the
clouds,” said Tom.
“Although you may not be able to raise any single kite to the altitude
you may desire, it is easy to accomplish your plan by a series of
kites; the string of the first being attached to the back of the
second, and so on.”
“How, papa? I do not exactly understand you.”
“Your kite,” said Mr. Seymour, “is now as high in the air, as the force
of the wind is capable of raising it; suppose you were to fix the end
of the string you hold in your hand to the back of another kite, would
not this second kite ascend as high as your first, by the same force,
and your first kite therefore rise to double the altitude it is at
present. In like manner you might attach a third kite, and so on.”
“Now I comprehend it; and I should much like to try the experiment,”
said Tom.
“You shall certainly witness the effect I have described; but you must
provide yourself with some stout string, for the force which the kites
exert when thus arranged, is greater than you can easily imagine;
indeed I question whether you would be able to hold them,” observed his
father.
Mr. Twaddleton here informed the young party that he had himself
witnessed a carriage containing three persons that had been drawn along
the road by kites, at the rates from fifteen to twenty miles an hour.
“I have seen the account of it,” said Mr. Seymour, “and if I remember
right, the principal kite was preceded at the distance of about 120
feet by a smaller pilot one, which served to direct it away from any
obstacles, such as trees, houses, &c. with which it might otherwise
have come in contact.”
“But how was the pilot kite made obedient to the will of the driver?”
asked Louisa.
“By means of strings so attached to it that its surface was easily made
to alter its angular position,” answered Mr. Seymour.
“If my twine should snap,” said Tom, whose attention was suddenly drawn
to his kite from a slight unsteadiness in its motion, arising from a
gust of wind, “we could easily recover it, that is one good thing; for
it is hovering over the open field at the end of the heath.”
“If you imagine that the kite, under such circumstances, would fall
upon the spot directly under it, you are much deceived: recollect that,
if the string should snap, the kite would be abandoned to two forces,
those of the wind, and its own gravity; and you will perceive that,
under such circumstances, it could not obey either of them, but would
fall in an intermediate or diagonal direction. This fact will be
rendered apparent by the annexed diagram. B A may be supposed to
represent the force and direction of the wind acting upon the kite, and
B D those of its gravity; then it is evident that, under the influence
of these joint forces, it would describe the diagonal, and, for reasons
already explained, that line must necessarily be the _curve_ B F.”
[Illustration: Diagram showing arc of fall trajectory.]
“Come,” said the vicar, “before Tom draws down his kite, let us send up
a _messenger_.”
“What may that be?” asked Louisa.
“A piece of paper or pasteboard, which, on being introduced upon the
string, is blown along the line up to the kite.”
The _messenger_ was accordingly prepared, and being placed upon the
string, it ascended as Mr. Seymour had anticipated. While this
operation was in progress, the vicar stood earnestly gazing upon the
kite, and, at length, burst forth in the following animated soliloquy:--
“Assuredly, this must be acknowledged as a most beautiful and imposing
toy! Fastidious or insensible must be that person, who does not feel
exhilarated as he gazes on the kite, proudly floating under the canopy
of heaven, and reflecting the departing smiles of the evening sun,
after it has ceased to cheer us below.”
“It has been said,” observed Mr. Seymour, “to the disparagement of
kite-flying, that as soon as the machine has been raised into the air,
and all the string let out, the excitement of the sport is at an end,
and that as nothing further can be achieved, the interest of the
performer from that moment begins to languish; now at this period the
_messenger_ will open a new source of pleasure and instruction, and
may, by a little ingenuity, be made to afford a great diversity of
amusement. I have therefore provided myself with several varieties of
this machine. Here is one in the form of a dragon, which, as it
ascends, produces a very striking and almost magical effect. See, there
it goes!”
The children were delighted, for the string upon which it was carried
became at a certain height invisible; so that the figure appeared like
a monster hovering in the air.
“I will now show you a _winged_ variety of this apparatus, which we
will name the _Brompton Messenger_.[44] It consists of a hollow
cylinder of stiff pasteboard, or thin wood, the diameter of which is
sufficiently large to allow its free revolution round the string of the
kite. To this cylinder are attached several flappers, or sails, in an
oblique direction, like those of a windmill, each of which is covered
with paper of a different colour. The action of the wind upon those
oblique surfaces necessarily occasions a rapid rotation, upon a
principle which I shall presently explain; and the beautiful effect
thus produced, as the whirling body ascends, must be seen before it can
be appreciated. I have some other contrivances of a similar nature,
which it is my intention to prepare for your future amusement.”(41)
“Has the kite ever been applied to any useful purposes?” asked Tom.
“Certainly,” answered his father. “It was by means of the kite that Dr.
Franklin was enabled to demonstrate the identity of electricity and the
cause of lightning, and thus to disclose one of the most awful
mysteries of nature.”
“Pray do tell us something about this electrical kite, papa,” said
Louisa.
“Not at present, my love; it would divert us too much from the subjects
in which we are engaged: at some future period I shall have much
pleasure in introducing you into these fairy regions of philosophy.”
“I just now remember reading in Miss Edgeworth’s Harry and Lucy,” said
Louisa, “something about a kite and Pompey’s pillar.”
“I am glad that you have reminded me of that story,” replied Mr.
Seymour: “I will relate it to you. Some English sailors laid a wager,
that they would drink a bowl of punch on the summit of Pompey’s pillar.
Now, that pillar is almost a hundred feet high, and it is quite smooth,
so that there was no way of climbing to the top, even for sailors, who
are such experienced climbers: so they flew their kite exactly over the
pillar, and when it came down on the opposite side, the string lay
across the top of the capital. By means of this string, they pulled a
small rope over, and by this a larger one, that was able to bear the
weight of a man; a pulley was then fastened to the end of the large
rope, and drawn close up to the upper edge of the capital; and then,
you perceive, they could easily hoist each other up. They did more, for
they hoisted the English flag on the top, and then drank the bowl of
punch, and won their wager.”
“That is a very good story,” said the vicar; “but I cannot help
regretting that so much ingenuity and labour should not have had a
nobler end to accomplish.”
“There is some truth in that observation,” said Mr. Seymour, “and I
will, therefore, relate another story which shall be more congenial to
your heart, and in which the kite will present itself in a more
interesting point of view; for, instead of enabling the sailors to
drink a bowl of punch at an altitude otherwise inaccessible, we shall
find it engaged in rescuing them from the horrors of shipwreck.”[45]
“Pray proceed, papa.”
“No, my dear, upon reflection, I think it will be better that we should
postpone the story, until your return to the lodge, when you shall read
it in ‘Harry and Lucy.’ I will also point out to you, in the same work,
an account of a new and useful application of the messenger, which will
prove to you how successfully the faculties of youth may be increased
and improved by those very amusements which are too generally regarded
as idle and unprofitable: I shall at the same time exhibit one or two
experiments in illustration of the nature and causes of wind.”
“Shall we not return immediately?”
“No, my dear; it would not be in my power to attend you at present; but
join me in the library after dinner; Mr. Twaddleton will now accompany
me to the village, and do you remain and enjoy the amusement of your
kite.”
It was not until the evening, that Tom and his sisters requested their
father to fulfil the promises he had made them in the morning.
“You told us,” said Louisa, “that you would give us some information
about the wind; the subject has been puzzling me ever since, for I
cannot make out the cause of it.”
“Wind, my love, is nothing more than air in motion; and is produced by
a large volume of it flowing in a current, or stream, from one place,
or region, to another, and with different velocities.”
“And what can produce these currents?” asked Tom.
“After the explanation of the action of the pump, I do not think that I
shall have much difficulty in making you understand the nature of the
operations by which wind is occasioned. Suppose a partial vacuum should
be formed in any region, would not the neighbouring air immediately
rush in to supply the deficiency and restore the balance?”
“Undoubtedly; from the pressure of the air behind it.”
“Heat,” continued Mr. Seymour, “will produce a partial vacuum, by
rarefying the air, and thus rendering it lighter; in consequence of
which, it will ascend, and the colder air will rush in to supply its
place.”
“I do not exactly see why the rarefied air should ascend,” observed
Louisa. “It appears to offer an exception to the general law of
gravity.”
“Not at all; on the contrary, its ascent is occasioned by the force of
gravity: in the first place, however, to prove the fact that heated air
does actually ascend, we have only to observe the direction of smoke,
as it issues from the chimney; this consists of minute particles of
fuel carried up, by a current of heated air, from the fire below; and
as soon as this current is cooled by mixing with that of the
atmosphere, the minute particles of coal fall, and produce the small
black flakes which render the air, and every thing in contact with it,
so dirty in a populous city.”
“But I want to know, papa, what it is which causes the hot air to
ascend?”
“The greater weight of the cold air above it, which gets, as it were,
beneath the lighter air, and obliges it to rise; just in the same way
as a piece of cork, at the bottom of an empty vessel, is made to rise
to the surface of the water which may be poured into it.”
“Now I understand it; pray, therefore, proceed with your account of the
wind. You have just said that heat rarefies the air, and causes it to
ascend.”
“And thus produces a current of air, or a _wind_.”
“Is heat, then, the cause of wind, papa?” asked Tom.
“It is one great cause; but there are, probably, several others; I
will, however, exemplify this subject by an experiment.”
So saying, Mr. Seymour produced a water-plate, a large dish, and a jug
filled with cold water. The bell was rung, and the servant entered with
a tea-kettle of boiling water.
The large dish was then filled with the cold, and the water-plate with
the boiling fluid.
“Let this large dish represent the ocean,” said Mr. Seymour, “and this
water-plate, which I will now place in its centre, an island in that
ocean; for the land, from receiving the rays of the sun, will be more
heated than the water, and will consequently rarefy the air above
it.--Now, Tom, light me the wax taper.”
“I have done so.”
“Then now blow it out.”
“I cannot imagine what you are about, papa;--‘Light the candle, and
then blow it out!’--but it still smokes, shall I put the extinguisher
over it?”
“By no means; give it to me, and observe what will happen when I carry
it round the edge of the dish.”
“The smoke goes to the centre,” exclaimed Tom.
“Showing, thereby, the existence of a current towards the water-plate,
or island; in consequence of the air above it having been heated, and
therefore rarefied. This explains in a very satisfactory manner, a fact
which may be constantly observed in our own climate, viz. a gentle
breeze blowing from the sea to the land in the heat of the day. Upon
the same principle it is, that most of the winds in different parts of
the globe may be readily accounted for.”(42)
“I suppose,” said Tom, “that the air must rush with great velocity, in
order to produce wind.”
“A very general error prevails upon this subject,” replied his father;
“the rate of motion has been greatly exaggerated. In a brisk gale,
even, the wind does not travel with such velocity, but that it may be
easily traced by the eye; and the sailor is able to watch its progress
by the ripple which it produces on the sea.”
“Has, then, the rate of its motion ever been estimated?” asked Louisa.
“When its velocity is about two miles per hour, it is only just
perceptible. In a high wind, the air travels thirty or forty miles in
the same period. In a storm, its rate has been computed as being from
sixty to eighty miles. It has also been ascertained, by experiment,
that the air, as it rushes from a pair of blacksmith’s bellows, has not
a velocity above that of five and forty miles in the hour.”
“At what rate should you think the air travelled this morning, when we
flew our kite?” enquired Louisa.
“I should think at about five miles an hour, for it was a pleasant but
gentle breeze.”
-----
Footnote 41:
The author has been thus minute, in order to afford his young friends
clear directions for constructing a kite, and which, as far as he
knows, are not to be found in any work hitherto published; and he
will also avail himself of this opportunity to state, that the thin
glazed linen of various colours, commonly known to haberdashers by
the name of lining, has been found to be the best material as a
covering for the kite. It is not only more durable than paper,
defying the most boisterous wind, but superior to it as being secure
from the effects of a shower of rain.
Footnote 42:
Those readers, who are inclined to enter more deeply into the
subject, may consult, with advantage, a memoir on the kite, by Euler,
published in the Transactions of the Academy of Berlin for the year
1756.
Footnote 43:
See p. 60.
Footnote 44:
From associations of an interesting nature connected with the
residence of the author’s children.
Footnote 45:
Transactions of the Society for the Encouragement of Arts, vol. xli.;
and Miss Edgeworth’s Harry and Lucy, vol. iv. p. 288.
------------------------------------------------------------------------
[Illustration: Children playing with paddles and a shuttlecock.]