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 completekite-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 toraise the wind, for the benefit of the vender, rather than to be raisedby 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, orback-boneof 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.”
Diagram of a kite.
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, atc, 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 bowd; 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 fromdacross the skeleton to the opposite notcha, giving it one turn round the lath in its way; fromait was carried tof, and wound round the top of the lath, and then again fastened atd; fromdit was extended rather more than midway down the lath, and having been secured atb, was finally carried to, and secured in the notcha. 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 offan 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 thebelly-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 thebelly-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, orplunge, 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 kiteplunges, 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 makingbobsfor 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 thesebobs, 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 atalewill 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 thelightsof science should beconsigned to the tallow-chandler! the works of the moralist, so well calculated topurifythe world, to the soap-seller! that such a book as ‘Laennec on theChest,’ with Dr. Forbes’s valuableCasesin the bargain, should bepackedoff to thetrunk-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 ofureicacid 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 ofDaniel’sProphecies.”
“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 thetail, of which it is to form a part.”
“Apposite allusion! impossible; as well mightyou 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 curtail?”
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 retail: pray, proceed.”
“We have next, I perceive, a prospectus for publishing all the speeches in the late parliament.”
“That is detail.”
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 entail; 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 willsoar 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 ortailof 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 everytale: 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 amthe manufacturer of a kite’s tail; and, surely, upon such an occasion,flightinessought 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 theSiberian sow-thistlehad closed itself the preceding evening, and theAfrican marigoldcontinued shut after seven o’clock in the morning, he had thought there would be rain; but,” he added, “that upon inspecting thepoor-man’s weatherglass, theAnagallis arvensis, orred 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?’
“‘Heu! quianam tanti cinxerunt æthera nimbi?’
“‘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 thekiteoriginated.
“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 directedthis 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,” repliedthe 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 ofcerf 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 kitecarries 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 inletting 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 wouldbe 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 properlyobserved, 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. thataction 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 birdrises,” answered Tom.
“Because the force of the stroke isgreaterthan the weight of the bird, and it therefore rises with thedifferenceof these two forces; were the strokelessthan its weight, then would it sink with the difference. Suppose, for example, a bird weighstwelveounces, and it strikes the air with a force equal tosixteen, is it not clear that it must rise with a force equal tofour? and is it not evident that, if it strikes the air with a force equal only toeight, that it must sink with a force equal tofour?”
“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 haveso 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 termedfeathering, 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.
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 lineWwill 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 lineYwill alone produce any effect, carrying the kite along the lineO 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 lineS T. The kite was therefore under the influence of the two forcesO AandS T, and, since these are in the direction of the two sides of a parallelogram, it would not obey either, but ascend throughO 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 tothis 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 subjecthereafter,” 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-fourdegrees, andforty-fourminutes,” 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 anobliquedirection 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.”