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."

At the time appointed 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 everything 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 waterplate 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."

"Now then 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." (43)

"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 s father; "the rate of motion has been greatly exaggerated. a brisk gale, even, the wind does not travel with such elocity, but that it may be easily traced by the eye; and e sailor is able to watch its progress by the ripple which it oduces on the sea."

"Has, then, the rate of its motion ever been estimated?" ked Louisa.

"When its velocity is about two miles per hour, it is only st. perceptible. In a high wind, the air travels thirty or rty miles in the same period. In a storm, its rate has been omputed as being from sixty to eighty miles. It has also een ascertained, by experiment, that the air, as it rushes om a pair of blacksmith's bellows, has not a velocity above hat of five and forty miles in the hour."

"At what rate should you think the air travelled this norning, when we flew our kite?" inquired Louisa.

"I should think at about five miles an hour, for it was a pleasant but gentle breeze."

Mr. Seymour now, at the earest request of the whole party who had been on the tiptoe of expectation, produced his "FLYING-TOP," of which the reader is here presented with a representation.

Fig. 59.

"This little machine," said Mr. Seymour, "consists, as you may observe, of a flyer, with three vanes, the form of each being that of the segment of a circle, the obliquity of

whose surface increases as it recedes from the centre of motion; this flyer, as you see, is attached to a spindle, around which the string that is to set it in motion is carefully wound, and the whole is adapted to a stand. Let us now join the vicar on the lawn, where we can conveniently put it into action."

The stump of a tree afforded a rest for the stand, which Mr. Seymour held firmly in an inclined position with his left hand, while with his right he vigorously pulled the string. Away whirled the flyer, and in a second, it rose majestically from the stand, and whizzing through the air, attained a very considerable altitude, no less to the astonishment than to the delight of the party. After several repetitions of the experiment, Mr Seymour thus proceeded to explain the philosophy of its flight.

"After the explanation you have already received regarding the flight of a bird, you will very readily understand the question before us. It is evident that the oblique vanes, by striking the air during their rapid rotation, must produce a reaction on their under surfaces."

"Exactly so," cried Tom; "and if that reaction be greater than is sufficient to counteract its gravity, the flyer must ascend in the air, just as the bird does in proportion to that excess.' ""

"You are quite right," continued his father, "and I need hardly remind you of the importance of attending to the angular adjustment of the vanes to ensure the greatest effect; it should be such as to make all the forces conspire, and you will recollect that the efficient force will be in a direction perpendicular to each inclined vane.'

A SHORT DISCOURSE. THE SHUTTLECOCK.-THE SOLUTION OF TWO PROBLEMS CONNECTED WITH ITS FLIGHT.THE WINDMILL. THE SMOKEJACK.-A TOY CONSTUCTED ON THE SAME PRINCIPLE.-THE BOW AND ARROW.- ARCHERY.-THE ARRIVAL OF ISABELLA VILLERS.

MR. TWADDLETON, on his arrival at the Lodge, on the following morning, was informed that Miss Villers was expected at Overton in the evening.

"Your account of that young lady," observed the vicar, has greatly prepossessed me in her favour; I only hope that she is not too blue."

"I care not how blue the stockings of a lady may be," said Mr. Seymour, "provided her petticoats be long enough to hide them;' and from my knowledge of Miss Villers, I can assure you, exalted as are her attainments, they are so veiled by feminine delicacy and reserve, that