considerable height above the horizon, whereas they are frequently not to be seen in clear weather from the high lands above the town. A much greater breadth of coast also appeared than is usually observed under the most favourable circumstances. The ordinary refractive power of the atmosphere is thus liable to be strikingly altered by a change of temperature and humidity, so that a hill which at one time appears low, may at another be seen towering aloft; and a city in a neighbouring valley, may from a certain station be entirely invisible, or it may show the tops of its buildings, just as if its foundations had been raised, according to the condition of the aerial medium between it and the spectator.

Of all instances of spectral illusion, the fata morgana, familiar to the inhabitants of Sicily, is the most curious and striking. It occurs off the Pharo of Messina, in the strait which separates Sicily from Calabria, and has been variously described by different observers, owing, doubtless, to the different conditions of the atmosphere at the respective times of observation. The spectacle consists in the images of men, cattle, houses, rocks, and trees, pictured upon the surface of the water, and in the air immediately over the water, as if called into existence by an enchanter's wand, the same object having frequently two images, one in the natural and the other in an inverted position. A combination of circumstances must concur to produce this novel panorama. The spectator, standing with his back to the east on an elevated place, commands a view of the strait. No wind must be abroad to ruffle the surface of the sea; and the waters must be pressed up by currents, which is occasionally the case, to a considerable height, in the middle of the strait, so that they may present a slight convex surface. When these conditions are fulfilled, and the sun has risen over the Calabrian heights so as to make an angle of 45° with the horizon, the various objects on the shore at Reggio, opposite to Messina, are transferred to the middle of the strait, forming an immovable landscape of rocks, trees, and houses, and a movable one of men, horses, and cattle, upon the surface of the water. If the atmosphere, at the same time, is highly charged with vapour, the phenomena apparent on the water will also be visible in the air, occupying a space which extends

from the surface to the height of about twenty-five feet. Two kinds of morgana may therefore be discriminated: the first, at the surface of the sea, or the marine morgana; the second, in the air, or the aerial. The term applied to this strange exhibition is of uncertain derivation, but supposed by some to refer to the vulgar presumption of the spectacle being produced by a fairy or magician. The populace are said to hail the vision with great exultation, calling every one abroad to partake of the sight, with the cry of " Morgana, morgana!" "On

Father Angelucci, an eye-witness, describes the scene in the following terms: the 15th of August, 1643, as I stood at my window, I was surprised with a most wonderful, delectable vision. The sea that washes the Sicilian shore swelled up, and became, for ten miles in length, like a chain of dark mountains; while the waters near our Calabrian coast grew quite smooth, and in an instant appeared as one clear polished mirror, reclining against the aforesaid ridge. On this glass was depicted, in chiaro scuro, a string of several thousands of pilasters, all equal in altitude, distance, and degree of light and shade. In a moment they lost half their height, and bent into arcades, like Roman aqueducts. A long cornice was next formed on the top, and above it rose castles innumerable, all perfectly alike. These soon split into towers, which were shortly after lost in colonnades, then windows, and at last ended in pines, cypresses, and other trees, even and similar. This was the Fata Morgana, which, for twenty-six years, I had thought a mere fable."

Brydone, writing from Messina, evidently in a dubious vein, states:-"Do you know, the most extraordinary phenomenon in the world is often observed near to this place? I laughed at it at first, as you will do, but I am now convinced of its reality, and am persuaded, too, that if ever it had been thoroughly examined by a philosophical eye, the natural cause must long ago have been assigned. It has often been remarked, both by the ancients and moderns, that in the heat of summer, after the sea and air have been much agitated by winds, and a perfect calm succeeds, there appears, about the time of dawn, in that part of the heavens over the straits, a great variety of singular forms, some at rest, and some moving about with great velocity. These forms, in proportion as the light increases, seem to become more aerial, till at last some time before sunrise they entirely disappear. The Sicilians represent this as the most beautiful sight in nature. Leanti, one of their latest and best writers, came here on purpose to see it. He says the heavens appeared crowded with a variety of objects: he mentions palaces, woods, gardens, &c., besides the figures of men and other animals, that appear in motion amongst them. No doubt the imagination must be greatly aiding in forming this aerial creation; but as so many of their authors, both ancient and modern, agree in the fact, and give an account of it from their own observation, there certainly must be some foundation for the story. There is one Giardini, a Jesuit, who has lately written a treatise upon this phenomenon, but I have not been able to find it. The celebrated Messinese Gallo has likewise published something on this singular subject. The common people, according to custom, give the whole merit to the devil; and indeed it is by much the shortest and easiest way of accounting for it. Those who pretend to be philosophers, and refuse him this honour, are greatly puzzled what to make of it. They think it may be owing to some uncommon refraction or reflection of the rays, from the water of the straits, which, as it is at that time carried about in a variety of eddies and vortices, must consequently, say they, make a variety of appearances on any medium where it is reflected. This, I think, is nonsense, or at least very near it. I suspect it is something of the nature of our aurora borealis, and, like many of the great phenomena of nature, depends upon electrical causes; which, in future ages, I have little doubt, will be found to be as powerful an agent in regulating the universe as gravity is in this age, or as the subtle fluid was in the last. The electrical

fluid in this country of volcanoes, is probably produced in a much greater quantity than in any other. The air, strongly impregnated with this matter, and confined betwixt two ridges of mountains-at the same time exceedingly agitated from below by the violence of the current, and the impetuous whirling of the waters-may it not be supposed to produce a variety of appearances? And may not the lively Sicilian imaginations, animated by a belief in demons, and all the wild offspring of superstition, give these appearances as great a variety of forms? Remember, I do not say it is so; and hope yet to have it in my power to give you a better account of this matter."

Ingenious as Brydone was, he here indulges a most unfortunate speculation, which, had he enjoyed the good fortune of personally observing the phenomenon, most likely, he would not have proposed. It is to be accounted for upon optical principles, which M. Biot, in his Astronomie Physique, thus applies, from Minasi's dissertation upon the subject: :- "When the rising sun shines from that point whence its incident ray forms an angle of forty-five degrees, on the sea of Reggio, and the bright surface of the water in the bay is not disturbed either by wind or current - when the tide is at its height, and the waters are pressed up by the currents to a great elevation in the middle of the channel; the spectator being placed on an eminence, with his back to the sun and hist face to the sea, the mountains of Messina rising like a wall behind it, and forming the background of the picture-on a sudden there appear in the water, as in a catoptric theatre, various multiplied objects-numberless series of pilasters, arches, castles, welldelineated regular columns, lofty towers, superb palaces, with balconies and windows, extended alleys of trees, delightful plains, with herds and flocks, armies of men on foot, on horseback, and many other things, in their natural colours and proper actions, passing rapidly in succession along the surface of the sea, during the whole of the short period of time while the above-mentioned causes remain. The objects are proved, by accurate observations of the coast of Reggio, to be derived from objects on shore. If, in addition to the circumstances already described, the atmosphere be highly impregnated with vapour and dense exhalations, not previously dispersed by the action of the wind and waves, or rarefied by the sun, it then happens that, in this vapour, as in a curtain extended along the channel to the height of above forty palms, and nearly down to the sea, the observer will behold the scene of the same objects not only reflected on the surface of the sea, but likewise in the air, though not so distinctly or well defined. Lastly, if the air be slightly hazy and opaque, and at the same time dewy, and adapted to form the iris, then the above-mentioned objects will appear only at the surface of the sea, as in the first case, but all vividly coloured or fringed with red, green, blue, or other prismatic colours."

Aerial images of terrestrial objects are frequently produced as the simple effect of reflection. Dr. Buchan mentions the following occurrence: "Walking on the cliff about a mile to the east of Brighton, on the morning of the 18th of November 1804, while watching the rising of the sun, I turned my eyes directly to the sea, just as the solar disc emerged from the surface of the water, and saw the face of the cliff on which I was standing represented precisely opposite to me, at some distance from the ocean. Calling the attention of my companion to this appearance, we soon also discovered our own figures standing on the summit of the opposite apparent cliff, as well as the representation of a windmill near at hand. The reflected images were most distinct precisely opposite to where we stood; and the false cliff seemed to fade away, and to draw near to the real one, in proportion as it receded towards the west. This phenomenon lasted about ten minutes, till the sun had risen nearly his own diameter above the sea. The whole then seemed to be elevated into the air, and successively disappeared. The surface of the sea was covered with a dense fog of many yards in height, and which gradually receded

before the rays of the sun." In December 1826 a similar circumstance excited some consternation among the parishioners of Miqué, in the neighbourhood of Poitiers, in France. They were engaged in the exercises of the jubilee which preceded the festival of Christmas, and about three thousand persons from the surrounding parishes were assembled. At five o'clock in the evening, when one of the clergy was addressing the multitude, and reminding them of the cross which appeared in the sky to Constantine and his army, suddenly a similar cross appeared in the heavens, just before the porch of the church, about two hundred feet above the horizon, and a hundred and forty feet in length, of a bright silver colour tinged with red, and perfectly well defined. Such was the effect of this vision, that the people immediately threw themselves upon their knees, and united together in one of their canticles. The fact was, that a large wooden cross, twenty-five feet high, had been erected beside the church as a part of the ceremony, the figure of which was formed in the air, and reflected back to the eyes of the spectators, retaining exactly the same shape and proportions, but changed in position and dilated in size. Its red tinge was also the colour of the object of which it was the reflected image. When the rays of the sun were withdrawn, the figure vanished.

The peasantry in the neighbourhood of the Harz Mountains formerly stood in no little awe of the gigantic spectre of the Brocken-the figure of a man observed to walk the clouds over the ridge at sunrise. This apparition has long been resolved into an exaggerated reflection, which makes the traveller's shadow, pictured upon the clouds, appear a colossal figure of immense dimensions. A French savant, attended by a friend, went to watch this spectral shape, but for many mornings they traversed an opposite ridge in vain. At length, however, it was discovered, having also a companion, and both figures were found imitating all the motions of the philosopher and his friend. The ancient classical fable of Niobe on Mount Sipylus belongs to the same category of atmospheric deceptions; and the tales, common in mountainous countries, of troops of horse and armies marching and countermarching in the air, have been only the reflection of horses pasturing upon an opposite height, or of the forms of travellers pursuing their journey. On the 19th of August 1820, Mr. Menzies, a surgeon of Glasgow, and Mr. Macgregor

began to ascend the mountain of Ben Lomond, about five o'clock in the afternoon. They had not proceeded far before they were overtaken by a smart shower; but as it appeared only to be partial, they continued their journey, and by the time they were half way up, the cloud passed away, and most delightful weather succeeded. Thin, transparent vapours, which appeared to have risen from Loch Lomond beneath, were occasionally seen floating before a gentle and refreshing breeze; in other respects, as far as the eye could trace, the sky was clear, and the atmosphere serene. They reached the summit about half-past seven o'clock, in time to see the sun sinking beneath the western hills. Its parting beams had gilded the mountain tops with a warm glowing colour; and the surface of the lake, gently rippling with the breeze, was tinged with a yellow lustre. While admiring the adjacent mountains, hills, and valleys, and the expanse of water beneath, interspersed with numerous wooded islands, the attention of one of the party was attracted by a cloud in the east, partly of a dark red colour, apparently at the distance of two miles and a half, in which he distinctly observed two gigantic figures, standing, as it were, on a majestic pedestal. He immediately pointed out the phenomenon to his companion; and they distinctly perceived one of the gigantic figures, in imitation, strike the other on the shoulder, and point towards them. They then made their obeisance to the airy phantoms, which was instantly returned. They waved their hats and umbrellas, and the shadowy figures did the same. Like other travellers, they had carried with them a bottle of usquebaugh, and amused themselves in drinking to the figures, which was of course duly returned. In short, every movement which they made, they could observe distinctly repeated by the figures in the cloud. The appearance continued about a quarter of an hour. A gentle breeze from the north carried the cloud slowly away; the figures became less and less distinct, and at last vanished. North of the village of Comrie, in Perthshire, there is a bold hill called Dunmore, with a pillar of seventy or eighty feet in height built on its summit in memory of the late Lord Melville. At about eight o'clock of the evening of the 21st of August of the present year, a perfect image of this well-known hill and obelisk, as exact as the shadow usually represents the substance, was distinctly observed projected on the northern sky, at least two miles beyond the original, which, owing to an intervening eminence, was not itself at all in view from the station where the aerial picture was observed. The figure continued visible for about ten minutes after it was first seen, and was minutely examined by three individuals. One of these fancied that there was a projection at the base of the monument, as represented in the air, which was not in the original; but, upon examining the latter the next morning, the image was found to have been more faithful than his memory; for there stood the prototype of the projection, in the shape of a clump of trees, at the base of the real obelisk.

In northern latitudes the effects of atmospheric reflection and refraction are very familiar to the natives. By the term of uphillanger the Icelanders denote the elevation of distant objects, which is regarded as a presage of fine weather. Not only is there an increase in the vertical dimensions of the objects affected, so that low coasts frequently assume a bold and precipitous outline, but objects sunk below the horizon are brought into view, with their natural position changed and distorted. In 1818, Captain Scoresby relates that, when in the polar sea, his ship had been separated for some time from that of his father, which he had been looking out for with great anxiety. At length, one evening, to his astonishment, he beheld the vessel suspended in the air in an inverted position, with the most distinct and perfect representation. Sailing in the direction of this visionary appearance, he met with the real ship by this indication. It was found that the vessel had been thirty miles distant, and seventeen beyond the horizon, when her spectrum was thus elevated into the air by this extraordinary refraction. Sometimes two images of a vessel are seen, the one erect and the other inverted, with their topmasts or