and turmoil and fiery tempest which can in a few days totally change the form of such a region, break it up into distinct parts-open up great abysses in one part, such as I have just described, and fill up others beside them!

"Now it has lately been ascertained by a careful comparison of all the recorded observations of the spots, that the periods of their scarcity and abundance succeed one another at regular intervals of a trifle more than

AURORAL FLAMES IN THE NORTHERN SKY.

five years and a-half: so that in eleven years and one-tenth, or nine times in a century, the sun passes through all its states of purity and spottiness. Now there are two classes of phenomena or facts which occur here on earth which stand in very singular accordance with the appearance and disappearance of the sun's spots. The first is that splendid and beautiful appearance in the sky which we call aurora or northern lights; and which, by comparison of the recorded displays, have been ascertained to be much more frequent in the years when the spots are abundant, and extremely rare in those years when the sun is free from spots.

"The other is a class of facts not so obvious to common observation, but of very great importance to us; because it is connected with the history and theory of the mariner's compass, and with the magnetism of the earth, which we all know to be the cause of the compass needle pointing to the north. But besides this (the oscillations already described), the needle is subject to irregular, sudden, and capricious variations-jerking as it were, aside, and oscillating backwards and forwards without any visible cause of disturbance. And, what is still more strange; these disturbances and jerks sometimes go on for many hours and even days, and often at the same instant of time, over very large regions of the globe; and in some remarkable instances, over the whole earth-the same jerks and jumps occurring at the same moments of time (allowance made for the difference of longitude). These occurrences are called magnetic storms, and they invariably accompany great displays of the aurora; and are very much more frequent when the sun is most spotted, and rarely or never witnessed in the years of few spots."

The history of auroral phenomena goes back to the time of Aristotle, who undoubtedly refers to the exhibition in his work on meteors, describing it as occurring on calm nights, having a resemblance to flame mingled with smoke, or to a distant view of burning stubble, purple, bright red, and blood-color being the predominant hues. Notices of it are likewise found in many of the classical writers; and the accounts which occur in the chronicles of the middle ages, of surprising lights in the air, converted by the imagination of the vulgar into swords gleaming and armies fighting, are allusions to the play of the northern lights. There is strong reason to believe, though the fact is perfectly inscrutable, that the aurora has been much more common in the European region of the northern zone, during the last century and a half, than in former periods.

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CHAPTER V.

IMAGES IN THE HEAVENS.

Optical Phenomenon at Buffalo-Topmasts Rising out of the Water-Deceitful Fog Bank-Extraordinary "Fata Morgana” in Sicily-A Spectacle that Excites the Populace-Ascribing the Mirage to the Devil-Prophecy Concerning Electricity-Prismatic Colors of Amazing Beauty-Troops of Clouds in the Sky— Heighth of Clouds-Poetical Fancies from Ossian-Mist on the Water-Accounting for Vapors-What Colors the Sun-The Great Orb Shorn of His Glories-Why the Sun is Red at Rising and Setting-Remarkable HalosStrange Mock Suns—Parhelia—Historic Halos—What Gassendi Saw-Parhelia Observed by Hevelius-Beautiful Sky Picture in Tennessee-Perfection of Creative Skill-Phenomena of Light-Wonderful Waves and Circles--Light a Magnificent Painter-Innumerable Vibrations.

few years ago, at Buffalo, an amusing optical illusion was observed, which was produced by fog. The following description is from one of the newspapers of that city: "A peculiar appearance was presented in the atmosphere over the lake on Saturday morning, the like of which had never been noticed before by those accustomed to daily intercourse with all the beauties and terrors peculiar to our waters. At an early hour some gentlemen, looking out upon the bay, discovered the top hamper and loftier sails of a vessel, apparently rising from the surface of the water, the hull and lower masts being entirely invisible. Soon another craft, similarly situated, was pointed out, and still the wonder grew.' It could not be that both these vessels had foundered and settled down so as to rest upon the bottom, on an even keel; yet there they were, as distinct as possible, sunk to their topmasts, the glassy surface of the water just reaching their lower mast heads.

"A tug was firing up, and when ready slowly steamed out into the lake. For a time there was nothing remarkable in her conduct; but suddenly she too sunk, and there was her smoke stack, just emerging from the deep, and ploughing through it without a ripple. It was a beautiful sight, rendered more so by the perfect placidity of the elements, the bright morning sun, and the soft, balmy temperature. The illusion grew out of a heavy fog bank, which lay upon the surface of the water, but did not obscure objects upon land; thus deceiving the eye as to the true level of the lake."

Of all instances of optical 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 slightly convex surface.

Strange Appearances on the Water and Above it.

When these conditions are fulfilled, and the sun has risen over the Calabrian heights, so as to make an angle of forty-five degrees 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 time is highly charged with vapor, 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 aërial. 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!"

"

Brydone, writing from Messina, states: 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 aërial, till at last some time before sunrise they entirely disappear. The Sicilians represent this as the most