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by M. Howel to be caused by a bitumen issuing from certain rocks at the bottom of the sea; the subtle parts of which, being attenuated and combined with the vapour, give it more consistence, and form a kind of aërial crystal, “which receives the light, reflects it to the eye, and transmits it to all the luminous points which colour the objects and render them visible.” Others attribute it to electrical causes.*

was his surprise on finding, at a distance of seven leagues from the spot, the town of which he had seen the reflection in the sky, and of which he had a sketch in his portfolio."

The most remarkable consequence of the refraction and reflection of light is the numerous atmospherical deceptions which are thereby produced. Places at a considerable distance are sometimes unexpectedly brought within the sphere of vision. Thus, in the year 1788, the coast of France was distinctly seen at Hastings. Towns, hills, valleys, islands, ships, &c., have been seen reflected in the heavens. In the county of Huntingdon, on the morning of July 16, 1820, at half past four o'clock, the sun then shining in a cloudless sky, and the light vapours that arose from the River Ouse moving over a little field near St. Neots, suddenly the village of Great Paxton, its farmhouses, barns, dispersed cottages, trees, and grass-fields, were clearly and distinctly visible in a beautiful aërial picture, which extended from east to west about four hundred yards. Nothing could exceed the surprise and admiration of the spectators as they beheld this surprising phenomenon, nor their regret at its disappearance in about ten minutes.

* The SPECTRE of the BROKEN is thus described by the Abbé Haüy. “Having ascended the mountain thirty times, I at last saw the spectre. It was at sunrise in the middle of May, about four o'clock in the morning. I saw distinctly a human figure of a monstrous size. The atmosphere was quite serene towards the east. In the southwest, a high wind carried before it some light vapours, which hung round the mountains upon which the figure stood. I bowed. The colossal figure repeated it. I paid my respects a second time, which was returned with the same civility. I then called the landlord of the inn; and, having taken the same position which I had occupied, we looked towards the mountain, when we saw two such colossal figures, which, after having repeated our compliments in bending our bodies, vanished. When the rising sun throws his rays over the Broken upon the body of one standing opposite to fleecy

MIRAGES.-ELECTRICAL APPEARANCES.

OPTICAL illusions are also frequently witnessed in hot countries just above the surface of the earth. These illusions are called MIRAGES. Humboldt saw one near the confluence of the Apure with the Oronoko, another in Caraccas, and a third in the Queen's Gardens. “When the sun appears," says he, “ the trunks of trees and rocks seem suspended in the air; and on the neighbouring beach the sands present the visual illusion of a sheet of water; a train of clouds suffices to seat the trunks of the trees and the suspended rocks again on the soil, to render the undulating surface of the plains motionless, and dissipate the charm which the Arabian, Persian, and Hindu poets have sung, as the soft delusion of the solitude of the desert." Johnson saw one on the northern borders of Persia, and Elphinstone another as he was travelling in Caubul, which seemed to exhibit a clear lake, and which reflected the figures of two gentlemen who were riding by its side as distinctly as if it had really been water.

These mirages are very frequent in Egypt, where two villages will appear like islands in the bosom of large sheets of water, with their inverted images as clearly defined as if they were real. These are described by Monge, Biot, and Belzoni.

The northern coast of Greenland, fringed with ice, reflecting all the primary colours of the sun's rays, often appears like an enchanted land ; and in the country north of Hudson's Bay, where the animals all wear the livery of winter, where wine freezes, and where rum and brandy coagulate, lunar

clouds, let him fix his eye steadfastly upon them, and in all probability he will see his own shadow extending the length of five or six hundred feet, at the distance of about two miles from him."

haloes and parhelias are frequent, sometimes stealing, as it were, colours from the rainbow. The stars appear crimson, and the aurora borealis is witnessed almost every night. In Spitzbergen, also, are seen many phenomena common to Greenland and Baffin's Bay, while at a distance from the coast are beheld large ice islands, floating in majestic masses like mountains. Against these the waters of the ocean are perpetually dashing, sometimes as high as their girdles, where, freezing, they form those curious pictures, which an active imagination converts into towns, villages, steeples, and temples. These, beheld in a hemisphere illumined by the aurora, where the stars are reflected from the snow, and the moon preserves a distinct horizon, present curious, eloquent, and awful pictures of magnificence.

Baron de Humboldt, when he was in the city of Cumana, witnessed a violent earthquake. A few days after, thousands of fireballs and falling stars were seen in the sky, rapidly succeeding each other for the space of several hours. From many of these stars issued irradiations like rockets and other fireworks. From what a height some of these meteoric appearances descended, may be inferred from the circumstance that innumerable falling stars and bolides, seen from three till six in the morning, were also observed at Maroa, 174 leagues southwest of Cumana; at San Gabriel, near the equator ; on the frontiers of Brazil, 230 leagues from Cumana ; also in the Gulf of Florida ; in Labrador and Greenland, and even at Weimar, in Germany. To be seen at such wide distances, these meteors must have been, according to Humboldt's calculation, 1233 miles in height. But it is more probable that these phenomena were not the same : the higher regions of the atmosphere, from some unknown cause, might have been in a state, through the whole of the area mentioned, peculiarly favourable to the production of

myriads of what the same philosophic traveller calls “ incandescences."

Men lived in and breathed electrical fluidity many thousand years, without being in any way conscious of its existence. This circumstance alone should be sufficient to place men on their guard how they fall into atheism when anything is seen, or an event occurs, of which they are unable to discover the immediate cause.

The cause of lightning is now generally understood : we shall, therefore, merely allude to a few instances of electrical phenomena.

Bosman relates, that during his stay at Elmina he found some old papers, in which it was recorded that, in a violent storm which occurred in 1651, the lightning had not only melted several swords without singing the scabbards, but melted gold and silver without consuming the bags.

Sometimes lights are seen upon the mastheads of ships. Dampier saw one in the Chinese seas after a violent storm of rain and thunder. It resembled a star; and Camoëns alludes to a similar phenomenon in the Lusiad. It is called by the Spanish and Portuguese, Corpus Sanctum; they esteem it an omen of fine weather, and go to prayers the moment they observe it.

Sometimes the entire sea appears like a floating mass of electrical fluid. On the coasts of NewGuinea are seen, for many leagues, a vast profusion of minute substances during the night. They are also observed on the coast of New-Holland, where they are generally of a grayish colour. In some seas they are red, and hence the fables of seas of blood, with which the world has occasionally been amused. Sailors call this collection sea sawdust. On the Australasian coast, Peron discovered, during a squall of wind, a broad belt of phosphoric light floating upon the water. Upon examination, he found it to proceed from innumerable animalculæ,

swimming at different depths. These proved to belong to a new genus of mollusca, to which Peron gave the name of pyrosoma.

The phosphorescent matter on the African coast is glutinous. In rainy nights it is not observable, but when the stars or the moon shine brightly, it is remarkably brilliant. The bodies composing this mass are regularly organized, and Dr. Solander and Sir Joseph Banks therefore naturally supposed them to be the spawn or eggs of a certain species of marine animal. These animalculæ are confined almost entirely to tropical seas. When they are separated from the water, it loses its phosphorescence, and the animalculæ soon lose it themselves when exposed to the dry air.

The province of New-Biscay, in North America, has an atmosphere which is sometimes so highly electrical, that sufficient matter may be collected from the fur of a bear to give considerable shocks; and as Saussure and Jalabert were crossing the Alps,

discovered their bodies to be so full of electrical fire that flashes darted from their fingers, their joints cracked, and they felt the same sensation as though they had been electrified by art.* On the coast of Upper Guinea, the atmosphere is frequently electrified to an astonishing degree. When Labillardière was sailing in those seas, he saw, during a dark night, a luminous column of great extent issue from under the clouds, and alight on the surface of

* The electric fluid will not melt ice or any congealed substance. It will not pass through hard stones, amber, oils, dry air, sulphur, or the ashes of animal and vegetable substances. In respect to the principal metals, they are all conductors; the best being gold, and the worst, lead. Wood, in its green state, is a conductor ; but when it is baked, a non-conductor. When it is burned to charcoal, it resumes its conducting qualities; but when reduced to ashes, it again becomes a non-conductor. The manner in which the electric fluid produces death is unknown, as no injury on the vessels or intestines appears on dissection.

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