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 decrees;

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 14

zinc, below his tongue, by bringing the outer edge of these pieces in contact, he will perceive a peculiar taste, and in the dark will see a flash of light. If he put a slip of tin-foil upon the bulb of one of his eyes, and a piece of silver in his mouth, by causing these pieces to communicate, in a dark place, a faint flash will appear before his eyes. Galvani supposed that the virtues of this new agent resided in the nerves of the animal, but Volta, who prosecuted this subject with much greater success, showed that the phenomena did not depend on the organs of the animal, but upon the electrical agency of the metals, which is excited by the moisture of the animal, whose organs were only a delicate test of the presence of electric influence. In exciting the electricity of the pieces of silver and zinc, the saliva of the mouth answers the same purpose as the moisture of the animal.

The conductors of the galvanic fluid are divided into the perfect and imperfect. The perfect conductors consist of metallic substances and charcoal: the imperfect are water and oxydated fluids, as the acids and all the substances that contain these fluids. To render the Galvanic, or more properly the Voltaic power sensible, the combination must consist of three conductors of the different classes. When two of the three conductors are of the first class, the combination is said to be of the first order; when otherwise, it is said to be of the second order. If a piece of zinc be laid upon a piece of copper, and upon the copper a piece of flannel, moistened with a solution of salt in water a circle of the first class is formed; and then if three other pieces be laid on these in the same order, and repeated several times, the whole will form a pile or battery of the first order. The ef fects may be increased to any degree, by a repetition of the same simple combination. The following is a cheap and easy method of constructing a Voltaic pile, for zinc is one of the cheapest of metals, and may be easily melted, like lead. Let a person cast twenty or thirty pieces of zinc, of the size of a cent, which may easily be done in moulds made of clay. Let him then take as many cents, and as many pieces of paper or woollen cloth cut in the same shape, and which he is to dip in a solution of salt and water. In building the pile, let him place a piece of zinc, wet paper, the supera bundant water being pressed out, after which the copper; then zinc, paper, copper, and so on, until the whole be

finished. The sides of the pile may be supported with rods of glass, or varnished wood, fixed in the board on which it is built. Having wet both hands, touch the lower part of the pile with one hand, and the upper part with the other, constant little shocks of electricity will be felt until one hand be removed. If the hand be brought back a similar repetition of shocks will be experienced. Hold a silver spoon in one hand, and touch with it the battery in the lower part, then touch the upper part with the tongue; the bitter taste is extreme. If the end of the spoon be put under the eyebrow, close to the ball of the eye, a sensation will be felt like the burning of red-hot iron, but which ceases the instant the spoon is removed. The plates will soon become oxydated, and require cleaning in order to make them act.

QUESTIONS.—1. What is galvanism? 2. Give an account of the origin of this branch of philosophy. 3. How may a person be made sensible of this kind of electric action? 4. What was the discovery of Volta? 5. What are perfect conductors of galvanic fluid?-imperfect? 6. What is necessary in order to render the galvanic or voltaic power sensible? 7. When is the combination said to be of the first order?-second order? 8. How may a pile or battery of the first order be formed? 9. What is a cheap and easy method of forming a voltaic pile? 10. What experiments may be formed with such a pile? 11. Why do the plates require cleaning? (See Voltaic pile, fig. 47.)

LESSON 71.

Galvanism (continued.)

Lab'oratory, a room fitted up with apparatus for the performance of chemical operations.

Deflagrate, to burn rapidly: nitre thrown on hot coals deflagrates. When accompanied with a loud noise it is termed deto-na'tion.

THE most convenient kind of galvanic battery consists of a trough made of baked wood, three inches broad, and about as deep; in the sides of the trough are grooves opposite to each other; into each pair of grooves is fixed, by cement, a plate of zinc and silver soldered together, and in the order of silver and zinc; the cement must be filled in so as to prevent any communication between the different cells. The cells are to be filled with water and nitrous acid, and then