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Ida. And so the kite slid down the plane when the boy clapped his hands and let the string slip through his silly fingers!

Frank. This reminds me of a very pretty piece of poetry about "the lost kite."

Mr. M. I am glad to find you so imbued with the poetry of science; and as this lesson has not been very poetical, you may repeat the piece, if you please.

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THE LOST KITE.

My kite! my kite! I've lost my kite!
Oh! when I saw the steady flight
With which she gained her lofty height,
How could I know that letting go

That naughty string would bring so low
My pretty, buoyant, darling kite,
To pass forever out of sight?

A purple cloud was sailing by,
With silver fringes o'er the sky;

And then I thought, it seemed so nigh,
I'd make my kite go up and light
Upon its edge so soft and bright,
To see how noble, high, and proud
She'd look while riding on a cloud!

As near her shining mark she drew,

I clapped my hands; the line slipped through
My silly fingers; and she flew

Away! away! in airy play,

Right over where the water lay!

She veered and fluttered, swung, and gave

A plunge, then vanished in the wave!

I never more shall want to look

On that false cloud or babbling brook;

Nor e'er to feel the breeze that took

My dearest joy, to thus destroy

The pastime of your happy boy.

My kite! my kite! how sad to think
She flew so high, so soon to sink!

"Be this," the mother said, and smiled,

"A lesson to thee, simple child!

And when, by fancies vain and wild

As that which cost the kite that's lost,

Thy busy brain again is crossed,

Of shining vapor then beware,

Nor trust thy joys to fickle air!

18.

"I have a darling treasure, too,

That sometimes would, by slipping through

My guardian hands, the way pursue

From which, more tight than thou thy kite,

I hold my jewel, new and bright,

Lest he should stray without a guide,)

To drown my hopes in sorrow's tide

19. Mr. M. There are many natural phenomena dependent on the atmosphere which we shall learn in the department of Physical Geography. But, before we conclude this lesson on

and ST; and since these are in the direction of the two sides of a parallelogram, it will not obey either, but ascend through O B, its diagonal. (See Fourth Reader, p. 298.) It is thus virtually pulled up the inclined plane O B.

pneumatics, I desire to read you a riddle, hoping each of you will be Edipus enough to guess the answer.

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A RIDDLE.

"Mortal', wouldst thou know my name',
Scan the powers I proudly claim'.
O'er this globe's capacious round
With fairy sprightliness I bound';
O'er sea and land my power extends,
To every herb my care descends.
Did I withhold my vital breath',
Nature's forms would sink in death'.
When confined, or swiftly driven
By angry spirits in the heaven',
My wrath in thunders I make known',
And Discord claims me as her own.
'Tis love of freedom makes me wild-
When uncontroll'd, my nature's mild;
And oft the nymph', in dewy grot',
Seeks solace from my plaintive note';
O'er lovers' graves I waft a sigh,
And breathe the sound of sympathy.

And know, ye sons of Albion's isle',
That when the Hero of the Nile,
Midst crowds with mournful pomp array'd,
In the cold lap of Earth was laid',
I sympathized with Britain's tear,
And waved the banner o'er his bier'.
'Tis I who from the trembling lyre
Breathe tones of love and soft desire';
'Tis I, the spirit of the shell,

Who fill with notes the listening dell';
And, when the war-trump sounds alarm',
'Tis I who summon men to arm'.
Made captive by the arts of man',
My various services began';

To grind his corn', to drain his lands,
I soon was tasked', to spare his hands'.
Should he to foreign climes proceed',
He yokes me like the neighing steed',
And, by my quick but easy motion',
He traverses the stormy ocean'.

His children, too, my presence court',
To give them toys', and make them sport':
Without my aid, their kites would lie
As useless weights, that ne'er could fly`;
Their humming-tops would soundless spin,
Unless I breathed a spell within':
The modest maid, without my power,
Would wither like her kindred flower.
Unless my cup of sweets she sips',
Where are the rubies of her lips?
Unless my glowing rouge she seeks',
Where are the roses of her cheeks?
What art again can strew her tresses
With half the grace my skill possesses'?
Ev'n goddesses are represented
In draperies which I invented.
Sometimes', 'tis true', I am so frail
As ruffian-like to raise your veil',

And thus to curious man reveal

The charms you modestly conceal'.
Revenge the deed'. Announce my Name',
For now you know the powers I claim'."

23. "It must be air," exclaimed the whole class with one

voice.

"But what is meant by the allusion to the funeral of the 'hero of the Nile ?'" said Ida.

Mr. M. I quote an extract from the description of the ceremonies of Nelson's interment in St. Paul's: "Never shall I forget the thrilling effect which was produced on the assembled multitude by the solemn movement of the banners in the dome as the bier slowly advanced along the aisle in the Cathedral; a movement which was accidentally occasioned by current of air from the western entrance, although, to the eye of fancy, it seemed as if some attendant spirit had directed the colors, under which the hero had bled and conquered, to offer this supernatural testimony of respect and sorrow."

LESSON VIII.-THE STEAM-ENGINE.

1. "You recollect," said Mr. Maynard, "that it was stated in a former lesson that water does not require to be so hot to boil when the pressure of the atmosphere is partially removed, as it does when it is subject to that pressure."

John. I recollect it, and I would ask if it does not require a higher temperature when the pressure is increased.

2. Mr. M. Under ordinary circumstances of the pressure of one atmosphere, of 15 pounds on the square inch, water boils at the temperature of 212°; but increase the pressure to 45 pounds on each square inch, or three atmospheres, and it will not boil below 275°.

Frank. There is a kind of kettle, made very strong, with an air-tight cover which is fastened down, and as the steam which first rises presses down by its elasticity, the water becomes hot enough to cook bones.

3. Mr. M. That is called Papin's Digester, and in it the water really never boils, but it becomes sufficiently hot to cause the separation of the gelatinous matter from bones. As this is used for soup, I suppose you call it cooking bones. Ella. I should not like to have one of those dangerous kettles in our kitchen, for fear it would burst.

Mr. M. It has an orifice closed with a plug, which is held down by a weight until a certain pressure is exerted by the steam, when it rises up and lets the steam escape. It then falls back again until the pressure becomes sufficient to raise it. 4. Ida. Is that what is called the safety valve? Mr. M. It is; and safety valves are used in all boilers where the steam is liable to be very much compressed.

George. In preparing for this lesson, I learned that one cubic inch of water will form about a cubic foot of steam, which will be condensed into a cubic inch of water again when cooled below the boiling-point. 5. Mr. M. You have learned in that fact the great principle on which the steam-engine acts. The instrument represented in the figure gives a clear idea of the elementary parts of what is called the low-pressure steam-engine.* It consists of a cylindrical glass tube, B, terminating in a bulb, A. In the tube a piston moves up and down, air-tight, and a little water having been placed in the bulb, it is brought to the boilingpoint by the application of a lamp. As the steam forms, it presses the piston upward by reason of its elastic force; but on dipping the bulb into cold water, the steam condenses, and produces a partial vacuum, and the piston is then driven downward by the pressure of the external air.

A

B

Fig. 34.

6. John. And if the rod attached to the piston were made to turn a crank, or work a lever, it would very well illustrate the working of a steam-engine.

*Low-pressure Engine, Fig. 35. The chief parts of this engine are the boiler, A, the cylinder, C, the piston-rod, I J, the condenser, L, and the air-pump, M. B is the steam-pipe, branching into two arms, communicating respectively with the top and bottom of the cylinder, and K is the eduction-pipe, formed of the two branches which proceed from the top and bottom of the cylinder, and communicating with the cylinder and the condenser. N is a

N

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cistern, or well of cold water, in
which the condenser is immersed.
Each branch of pipe has its own
valve, as F, G, P, Q, which may
be opened or closed as the occa-
sion requires. Suppose, first, that
all the valves are open, while
steam is issuing freely from the boiler. It is easy to see that the steam
would circulate freely throughout all parts of the machine, expelling the
air, which would escape through the valve in the piston of the air-pump,
and thus the interior spaces would all be filled with steam. This proc-
ess is called blowing through; it is heard when a steam-boat is about set-
ting off. Next, the valves F and Q are closed, G and P remaining open.
pressing the cylinder forces it down, and the instant when it begins to descend the stop-
cock O is opened, admitting cold water, which meets the steam as it rushes from the cyl-
inder, and effectually condenses it, leaving no force below the piston to oppose its descent.
Lastly, G and P being closed, F and Q are opened, the steam flows in below the piston,
and rushes from above it into the condenser, by which means the piston is forced up again
with the same power as that with which it descended. Meanwhile the air-pump is play.
ing, and removing the water and air from the condenser.

The steam now

Mr. M. Can George now tell in what respect the highpressure steam-engine differs from the low-pressure?

George. In the high-pressure engine, the steam, being admitted first on one side of the piston and then on the other, is pushed out against the atmosphere; but in the low-pressure, a partial vacuum is produced alternately on each side of the piston by allowing the steam to escape into a fountain of cold water, which condenses it.

7. Mr. M. I have here a very interesting description of the steam-engine, and of its wonderful power and multiplied uses, by Dr. Arnott, and I will read the closing part of it to you. In the view here taken of it, you see the steam-engine is not only a wonderful instrument in itself, but one of the most effective instruments of human progress and civilization ever invented.

8. "It regulates with perfect accuracy and uniformity the number of its strokes in a given time, counting or recording them, moreover, to tell how much work it has done, as a clock records the beats of its pendulum; it regulates the quantity of steam admitted to work, the briskness of the fire, the supply of water to the boiler, the supply of coals to the fire; it opens and shuts its valves with absolute precision as to time and manner; it oils its joints; it takes out any air which may accidentally enter into parts which should be vacuous; and when any thing goes wrong which it can not of itself rectify, it warns its attendants by ringing a bell.

9. "Yet with all these talents and qualities, and even when exerting the power of six hundred horses, it is obedient to the hand of a child. Its aliment is coal, wood, charcoal, or other combustibles; it consumes none while idle; it never tires, and wants no sleep; it is not subject to malady when originally well made, and only refuses to work when worn out with age; it is equally active in all climates, and will do work of any kind; it is a water-pumper, a miner, a sailor, a cotton-spinner, a weaver, a blacksmith, a miller, etc., etc.; and a small engine, in the character of a steam pony, may be seen dragging after it on a rail-road a hundred tons of merchandise, or a regiment of soldiers, with greater speed than that of our fleetest coaches. It is the king of machines, and a permanent realization of the genii of Eastern fable, whose supernatural powers were occasionally at the command of man."

10. Frank. Dr. Arnott speaks of a steam pony which is used on a rail-road. This must be the very pony which gave the poet Saxe such a pleasant "ride on the rail,"

"Singing through the forests,

Rattling over ridges,

Shooting under arches,

Rumbling over bridges;

Whizzing through the mountains,

Buzzing o'er the vale,

Bless me! this is pleasant,

Riding on the rail!"

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11. Mr. M. It would have been fortunate if poets had written more on scientific and philosophical subjects, as the lan

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