THUNDER AND LIGHTNING.

153

imagined before his time that a similarity existed between lightning and the electric fluid; but Franklin brought this supposition to the test, and proved the truth of it by the simple means of a boy's kite covered with a silk handkerchief instead of paper, and some wire fastened in the upper part, which served to collect and conduct the fluid. When he had raised this machine into the atmosphere, he drew electric fluid from the passing clouds, which descended through the flaxen string of the kite as a conductor, and was afterwards drawn from an iron key which he tied to the line at a small distance from his hand. This important experiment immediately led to the formation of conductors to secure buildings from the effects of lightning.

When aqueous vapour is condensed, the clouds formed are usually more or less electrical, and the earth below them being brought into an opposite state, a discharge takes place when the clouds approach within a certain distance, constituting lightning; and the collapsing of the air, which is rarefied in the electrical circuit, is the cause of the thunder, which is more or less intense, and of longer or shorter duration, according to the quantity of the air acted upon, and the distance of the place where the report is heard from the point of the discharge.

In gloomy pomp, whilst awful midnight reigns,

And wide o'er earth her mournful mantle spreads,
Whilst deep-voiced Thunders threaten guilty heads,
And rushing torrents drown the frighted plains,
And quick-glanced Lightnings, to my dazzled sight,
Betray the double horrors of the night:

A solemn stillness creeps upon my soul,
And all its powers in deep attention die;
My heart forgets to beat; my steadfast eye
Catches the flying gleam; the distant roll,
Advancing gradual, swells upon my ear
With louder peals, more dreadful as more near.

Awake, my soul, from thy forgetful trance!
The storm calls loud, and meditation wakes;
How at the sound pale Superstition shakes,
Whilst all her train of frantic fears advance!

Children of darkness, hence! fly far from me!
And dwell with guilt and infidelity!

But come, with look composed, and sober pace,
Calm Contemplation, come! and hither lead
Devotion, that on earth disdains to tread;
Her inward flame illumes her glowing face,
Her upcast eye, and spreading wings, prepare
Her flight for heaven to find her treasure there.
She sees, enraptured through the thickest gloom,
Celestial beauty beam, and 'midst the howl
Of warring winds, sweet music charms her soul;
She sees while rifted oaks in flames consume,

A FATHER GOD, that o'er the storm presides,
Threatens, to save, and loves, when most he chides.

CHAPONE.

QUESTIONS.-1. What is the description of the Leyden phial? 2. How is it charged?—how discharged? 3. What experiment may be made by it? 4. What is an electrical battery? 5. What great discovery did Dr. Franklin make, and by what means? 6. To what did this experiment lead? 7. What is lightning ?-thunder? (See Leyden phial, fig. 50.)

LESSON 69.

Falling Stars, Water Spouts, and Northern Lights.

Lam bent, playing about, gliding over.

Glo'ry, a circle of rays which surrounds the heads of saints in pictures, praise, celebrity, felicity of heaven.

It is supposed to be owing to the electricity of the atmosphere, that we observe a number of curious and interesting phenomena, such as falling stars, water-spouts, and northern lights. What are called falling stars are seen chiefly in clear and calm weather: it is then that the electric fluid is probably not very strong, and passing through the air it becomes visible in particular parts of its passage, according to the conducting substances with which it may meet. One of the most striking of this kind is recorded by Beccaria, an Italian. As he was sitting with a friend in the open air, an hour after sun-set, they saw a falling, or as it is sometimes

called, a shooting star, directing its course towards them, growing apparently larger and larger, till it disappeared not far from them, and, disappearing, it left their faces, hands, and clothes, with the earth, and neighbouring objects, suddenly illuminated with a diffused and lambent light, attended with no noise at all. He concluded this to be the effect of electricity, because he had previously raised his kite, and found the air very much charged with the electric matter : sometimes he saw it advancing to his kite like a falling star; and sometimes he saw a kind of glory round it, which followed it as it changed its place.

Water-spouts are often seen in calm weather; and the sea seems to boil and send up smoke under them, rising in a sort of hill towards the spout. A rumbling noise is often heard at the time of their appearance, which happens generally in those months that are peculiarly subject to thunderstorms, and they are commonly accompanied or followed by lightning. When these approach a ship, the sailors present and brandish their swords to disperse them, which seems to favour the conclusion that they are electrical. The analogy between water-spouts and electricity may be made visible by hanging a drop of water to a wire, communicating with the prime conductor, and placing a vessel of water under it. In these circumstances, the drop assumes all the various appearances of a water-spout, in its rise, form, and mode of disappearing. It is inferred, therefore, that the immediate cause of this extraordinary phenomenon is the attraction of the lower part of the cloud for the surface of the water.

The northern light (Aurora Borealis) is an extraordinary meteor, or luminous appearance, showing itself in the night, in the northern part of the heavens; and most frequently in frosty weather. It is usually of a reddish colour inclining to yellow, and sends out frequent coruscations of pale light, which seem to rise from the horizon in the form of a pyramid with undulating motion, and shoot with great velocity up to the zenith. This kind of meteor, which is more uncommon as we approach towards the equator, appears with the greatest lustre in the polar regions, and during the long winter is almost constant. In Sweden and Lapland, the northern lights are not only singularly beautiful in their appearance, but afford travellers by their almost constant effulgence a very beautiful light during the whole night. In

Hudson's bay, they diffuse a variegated splendour, which is said to equal that of the full moon. In the north eastern parts of Siberia, they have been described as beginning with single bright pillars, rising in the north, and almost at the same time in the north-east, which gradually increasing comprehend a large space of the heavens, rush about from place to place with incredible velocity, and finally almost cover the whole sky. The northern lights are supposed to be electrical phenomena, because electricians can readily imitate the appearance with their experiments. Dr. Franklin's idea is that they may arise from a discharge of electricity, accumulated in the atmosphere near the poles, into its rarer parts. On the Northern Lights.

BY LOMONOSOV, A RUSSIAN POET-TRANSLATED BY J. BOW

RING.

WHERE are thy secret laws, O nature, where?
Thy north lights dazzle in the wintry zone :
How dost thou light from ice thy. torches there?
There has thy sun some sacred, secret throne ?
See in yon frozen seas what glories have their birth ;
;
Thence night leads forth the day to illumine the earth.
Come then, philosopher! whose privileged eye
Reads nature's hidden pages and decrecs;

Come now, and tell us whence, and where, and why,
Earth's icy regions glow with lights like these,
That fill our souls with awe; profound inquirer, say;
For thou dost count the stars and trace the planets' way!
What fills with dazzling beams the illumined air?
What wakes the flames that light the firmament?
The lightning's flash? there is no thunder there--
And earth and heaven with fiery sheets are blent;
The winter night now gleams with brighter, lovelier ray
Than ever yet adorned the golden summer's day.

Is there some vast, some hidden magazine,
Where the gross darkness flames supplies?
Some phosphorus fabric, which the mountains screen,
Whose clouds of light above those mountains rise?
Where the winds rattle loud around the foaming sea,
And lift the waves to heaven in thundering revelry?

Thou knowest not! 'tis doubt, 'tis darkness all! E'en here on earth our thoughts benighted stray, And all is mystery through this worldly ballWho then can reach or read yon milky way? Creation's heights and depths are all unknown, untrod; Who then shall say how vast, how great, creation's God? QUESTIONS.-1. Why is it supposed that those meteoric appearances called falling stars owe their origin to electricity? 2. How may the analogy between electricity and the water-spout be made visible? 3. Describe the northern light. 4. What is Dr. Franklin's idea of it? [NOTE. A similar light called aurora australis has been long since observed towards the south pole.]

LESSON 70.
Galvanism.

Mus'cle, the fleshy fibrous part of an animal body. GALVANISM is another mode of exciting electricity. In electricity the effects are chiefly produced by mechanical action; but the effects of galvanism are produced by the chemical action of bodies upon each other. This branch of philosophy has been denominated galvanism, from Galvani, an Italian professor, whose experiments led to its discovery. In 1789, he was by accident led to the fact of electricity having the property of exciting contractions in the muscles of animals. After having observed that common electricity, even that of lightning, produced vivid convulsions in the limbs of recently killed animals, he ascertained that metallic substances, by mere contact, under particular circumstances, excited similar commotions. He found it to be essential that the forces of metals employed should be of different kinds. He applied one piece of metal to the nerve of the part, and the other to the muscle, and afterwards connected the metals, either by bringing them together, or by connecting them by an arch of a metallic substance; every time this connexion was formed, the convulsions took place. The greatest muscular contractions were found to be produced by zinc, silver, and gold. A person may be made sensible of this kind of electric action by the following experiments. If he place a piece of one metal, as a half crown above, and a piece of some other metal, as