ed. The evening was fine and clear, the wind westerly. The aurora first appeared in the north, and gradually extended in a luminous arch across the zenith, almost to the southern horizon. A dim sheet of light then suddenly appeared, and spread over the whole of the heavens to the eastward of the magnetic meridian, while only a few insulated specks were visible to the westward. The eastern aurore were grey and obscure, and exhibited little motion; but the arch extending across the zenith, showed an uncommon playfulness of figure and variety of form. Sometimes it exhibited a luminous edge towards the west, in some places concentrated into a fervid brilliancy. The rays were a little oblique to the position of the arch; but generally parallel to each other, and commonly ran in the direction of the magnetic north and south. At one time they extended sideways against the wind; at another in the contrary direction. Now they shot forward numerous luminous pencils, then shrunk into obscurity, or dispersed into the appearance of mere vapour. colours were yellowish-white and greyish-white. All the stars of the fourth magnitude were visible through the meteor, even in its most vivid coruscations. Ursa Major was at one time encircled with such a characteristic blazonry of light, that the Bear seemed to spring into figure, and to be shaking his shaggy limbs, as if in contempt of the less distinguished constellations around him. The Pleiades were almost observed by the light produced by the aurora; though Venus, and all the superior stars, shone with becoming splendor. I have never been sensible that the shooting of the aurora was accompanied by any noise; the The turbulence, indeed, of the water at sea, or noise of the sails during calms, prevent the light sounds from being heard. Earthquake in Chile.-A government Gazette of Chile, published ber, contains an account of this at Santiago on the 27th of Novemdreadful calamity. rector, who happened to be at Val- dated Santiago, 22nd November; On the 19th November, at ten rarefaction of the air, having been previously observed for three or four hours, a horrible noise announced, and by a few seconds preceded, an earthquake such as had not been experienced in Chile since 1730: its explosion showed itself by two strong shocks, which lasted two minutes and a half or three minutes; the latter, stronger than the first, was only of about twenty seconds. It was at first thought that the whole city was destroyed: the consternation was general, but fortunately no lives were lost, and only a few persons were hurt by falling fragments or tiles. The action of the earthquake was of the trembling description, and its direction from N.E. to S.W. Some walls of the churches of La Merced, San Augustin, San Francisco, &c., have fallen down; the Mint, the interior of the Cathedral, the directorial Palace, the steeples of the Treasury, and of the prison, are also damaged, and in some places threaten to come down. The walls of houses which were not very solid are much damaged. The earth was almost constantly in motion, though slight and only perceptible by the pendulum; but at times there were smart and sharp shocks. strong twilight. It is reported, that various other small meteors were seen towards the Cordillera. At 5h. 24m., there was another slight shock, preceded by considerable noise. Shocks succeeded each other rapidly, and increased the consternation, especially amongst women; most families have abandoned the city and retired to the neighbouring country houses; the lower classes are encamped in the public squares, the dikes, and aqueducts. On the 21st, at 4h. 25m. in the morning, and at 11h. 5m., other slight shocks were felt. Several families came to town to spend the day in their houses, with an intention to return to the country and to sleep there. The moon was full at 6h. 30m. p. m. This day, at 4h. 20m. in the morning, and 9h. 12m. and 9h. 22m. three smart shocks; they continue to this hour, seven o'clock in the afternoon; but some of them almost imperceptible. Scheme for sending Despatches to the East Indies by a SteamPacket.-The Royal George, sir John M. Doyle, ran from Vigo to Plymouth in 84 hours, being nine and a half degrees, 570 geographie or sea miles; and from Plymouth to Portsmouth in 20 hours, being 135 miles; the former was at the rate of six miles six furlongs and a quarter, the latter nearly at the same rate. The following calculation in smoother seas is at eight miles, and on land at the rate of five miles an hour : On the 20th, at 3h. 8m. in the morning, there was a slight shock, without any sensible noise: at 3h. 42m., a meteor ran in the same direction as the earthquake, from N.E. to S.W., in the form of a large train of fire, which for about four seconds produced a sort of From London to Marseilles, or Toulon, in France 540 4 12 by land. From the coast of France to Malta. From Malta to Alexandria in Egypt From Alexandria, by Cairo, to Suez From Suez to Mocha, in the Arabian Gulf. From Mocha to Bombay ..... .... 600 3 3. by sea. 2 12 480 by sea. 120 1 O by land. 1020 70 by sea. 1500 7 19 by sea. 4260 24 6 If by sea, and round the southern coast of Africa, it will stand thus nearly seven geographical miles an hour :- From Lisbon to the Cape Verd Islands 720 6 4 6-7 1430 8 12 2-7 2160 12 17 4-7 .... 1800 10 17 1-7 ...... 2100 12 12 1800 10 17 1-7 10,010 61 CHEMISTRY. A new Fluid, with remarkable Physical Properties, discovered in the Cavities of Minerals.-A new fluid, of a very singular nature, has been recently discovered by Dr. Brewster, in the cavities of minerals. It possesses the remarkable property of expanding about thirty times more than water; and, by the heat of the hand, or between 75° and 83°, it always expands so as to fill the cavity which contains it. The vacuity, which is thus filled up, is, of course, a perfect vacuum; and at a temperature below that now mentioned, the new fluid contracts, and the vacuity re-appears, frequently with a rapid effervescence. These phenomena take place instantaneously, in several hundred cavities, at the same time. The new fluid is also remarkable for its extreme volubility; adhering very slightly to the sides of the cavities; and is likewise distinguished by its optical properties. It exists, however, in quantities too small to be susceptible of chemical analysis. This new fluid is almost always accompanied with another fluid like water, with which it refuses to mix, and which does not perceptibly expand at the above-mentioned tem perature. In a specimen of Cymophane, or Chrysoberyl, Dr. Brewster has discovered a stratum of these cavities in which he has reckoned, in the space of 1-7th of an inch square, thirty thousand cavities, each containing this new fluid, a portion of the fluid like water, and a vacuity besides. All these vacuities simultaneously disappear at a temperature of 83°. If such a fluid could be obtained in quantities, its utility in the construction of thermometers and levels would be incalculable. There are many cavities in crystals, such as those opened by sir Humphrey Davy, which contain only water, and which, of course, never exhibit any of the properties above described. Method of forming Three Haloes artificially round the Sun, or any luminous object.-The following experiment, which illustrates in a pleasing manner the actual formation of Haloes, has been given by Dr. Brewster ;-Take a saturated solution of alum, and having spread a few drops of it over a plate of glass, it will rapidly crystallize in small flat octohedrons, scarcely visible to the eye. When this plate is held between the observer and the sun, or a candle, with the eye very close to the smooth side of the glass plate, there will be seen three beautiful haloes of light, at different distances from the luminous body. The innermost halo, which is the whitest, is formed by the images refracted by a pair of faces of the octohedral crystals, not much inclined to each other; the second halo, which is more coloured, with the blue rays outwards, is formed by a pair of faces more inclined; and the third halo, which is very large and highly coloured, is formed by a still more inclined pair of faces. Each separate crystal forms three images of the luminous body, placed at points 120° distant from each other, in all the three haloes; and as the numerous small crystals have their refracting faces turned in every possible direction, the whole circumference of the haloes will be completely filled up. The same effects may be obtained with other crystals; and when they have the property of double refraction, each halo will be either doubled, when the double refraction is considerable, or rendered broader, and otherwise modified in point of colour, when the double refraction is small. The effects may be varied, by crystallizing upon the same plate of glass, crystals of a decided colour, by which means we should have white and coloured haloes succeeding each other.-Edin. Phil. Jour. Variation in the Bulbs of Thermometers.-In mercurial thermometers, with a perfect vacuum above the mercury, M. Flauguergues has observed, that the freezing point has gradually risen nine tenths of a degree, and has gone on increasing for years. He attri butes this to a permanent change of form, produced by the constant pressure of the atmosphere on the bulb. He therefore recommends, that thermometers should be made with open terminations. The same fact had been long before observed by M. Angelo Bellani, of Milan, who mentions a very pretty experiment, for shewing that it arises from the glass. Take a mercurial thermometer, which has not been exposed for some months to temperatures near that of boiling water, whose scale rises to the boiling point or higher, and whose degrees are at least a line long, so that tenths of a degree can be easily seen. Having carefully marked the freezing point, plunge it in boiling water, and, upon replacing it in melting ice, it will be found, that the freezing point has sunky's of a degree, in consequence of the expanded glass not having resumed accurately its original form. Hence it follows, that the new barometer of the rev. Mr. Wollaston must be liable to error from this cause.Bibl. Univers. New Form of the Voltaic Apparatus.-Mr. Pepys has constructed, at the London Institution, a single coil of copper and zinc plate, consisting of two sheets of the metals, each fifty feet long, by two feet broad, having therefore a surface of 200 square feet; they are wound round a wooden centre, and kept apart by pieces of hair-line, interposed at intervals between the plates. This voltaic coil is suspended by a rope and counterpoise over a tub of dilute acid, into which it is plunged when used. It gives not the slightest electrical indications to the electrometer; indeed, its electricity is of such low intensity, that well-burnt charcoal acts as an insulator to it; nor does the quantity of electricity appear considerable, for it with difficulty ignites one inch of platinum wire of inch diameter. When, however, the poles are connected by a copper wire inch diameter and 8 inches long, it becomes hot, and is rendered most powerfully magnetic, and the instrument is admirably adapted for all electromagnetic experiments. Expansive force of Coal Gas The whole mechanical power of an explosion of 15,000 cubic feet of a mixture of coal gas, and common air, is equal to that of the explosion of 6 cubic feet, or 4 barrels of gunpowder; and if we suppose the heated gases in both cases to escape, and mix with the common air in a building containing 30,000 cubic feet, so as to produce an effect commensurate to the temperature of the whole mixture, the explosion of about 15 cubic feet, or 10 barrels of gunpowder, would be required, in order to produce, like the gas, a force of about 10 atmospheres for the whole space. It must, however, be recollected, that gunpowder, thus disposed, is very unfavourably situated for producing violent effects; and that a much smaller quantity, in ordinary cases, would be more formidable than the explosion of the coal gas.-A more precise idea of the effects of such an explosion may be obtained from the calculation of its projectile effects, which would carry some parts of the wall of the surrounding building to a height of nearly 150 yards, and others to a distance of nearly 300. If the walls were in immediate contact with the gasometer, the height and distance would be about twice as great. But a roof of carpentry and tiles being lighter, would be carried higher, while the lateral force of the explosion would be diminished.-Supposing the explosion of the gas to be unconfined, the shock would throw down a inches thick, at the distance of brick wall, 9 feet high, and 18 about 50 feet from the centre; it would probably break glass windows at 150 yards, and at 300, would produce an effect similar to very high wind. the instantaneous impulse of a Scoresby has instituted a series of Magnetism by Percussion-Mr. experiments, to determine magnetism by percussion with more precision; and some of his results deserve attention. When a bar of long, and a quarter of an inch soft-steel, six inches and a half diameter, held vertically, and resting upon freestone, was struck 17 blows with a hammer, it acquired the power of lifting 6 grains? 22 blows did not augment the force. When the bar rested vertically upprived of magnetism), 42 blows on a parlour poker (previously degave it the power of lifting 88 grains, and 90 blows, with a larger hammer, augmented the lifting power to 130 grains. The poker was also rendered magnetic. Farther hammering rather diminished inverting the bar, a single blow than increased the power. nearly destroyed the magnetism; two blows changed the poles. Hammering the bar in the plane of the magnetic equator, also destroyed the polarity. The magnetwhen the length of the bars was ism by percussion was augmented increased. On Chronometers, by P. Lecount, Esq. On the Effects of Magnetism on I find, says he, that the subject nometers has employed Mr. Barof the iron in ships affecting chrolow's attention as well as my own, |