CHAPTER XIV.

THE WEATHER, WITH THE HOPES AND FEARS WHICH IT ALTERNATELY INSPIRED. -THE ORACULAR FLOWERS. PREPARATIONS FOR THE FLIGHT OF THE KITE.-A DISCOURSE ON THE THEORY OF FLYING. THE STRUCTURE AND ACTION OF THE WINGS OF THE BIRD. -A PHILOSOPHICAL DISQUISITION UPON THE FORCES BY WHICH THE ASCENT OF THE KITE IS ACCOMPLISHED. THE TAIL OF THE BIRD COMPARED WITH THE RUDDER OF A SHIP.- THE TAIL OF THE KITE.- THE ALTITUDE TO WHICH THE KITE CAN ASCEND HAS A DEFINED LIMIT. A SERIES OF KITES ON ONE STRING.- A KITE CARRIAGE.-THE MESSENGER.- THE CAUSES, DIRECTION, AND VELOCITY, OF WIND EXPLAINED. THE FLYING TOP.

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; (34) after which, I shall be able lo 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! quinam 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? (35) 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!"

On the arrival of the party at Overton Heath, the weather was found propitious to their adventure; 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. Sey

mour.

"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?" inquired 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, (36) 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 round 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 inquiry, which cannot be successfully treated without a knowledge of the higher branches of the mathematics; but I shall, of course, avoid all such difficulties.* 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,† viz. that action and reaction

*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.

† See page 72.