THE MIRAGE OF THE POLAR SEAS. 209 tricks, and on no occasion have I witnessed the exhibition to such perfection. The atmosphere had a rare softness, and throughout almost the whole day there was visible a most remarkable mirage, or refraction, an event of very frequent occurrence during the calm days of the Arctic summer. The entire horizon was lifting and doubling itself continually, and objects at a great distance beyond it rose, as if by strange enchantment, and stood suspended in the air, changing shape with each changing moment. Distant icebergs and floating ice-fields, and coast-lines and mountains, were thus brought into view-sometimes preserving for a moment their natural shapes, then widening and lengthening, rising and falling, as the wind fluttered or fell calm over the sea. The changes were as various as the dissolving images of a kaleidoscope, and every form the imagination could conceive stood out against the sky. At one moment a sharp spire, the prolonged image of a distant mountain-peak would shoot up, and this would fashion itself into a cross, or a spear, or a human form, and would then die away, to be replaced by an iceberg, which appeared as a castle standing upon the summit of a hill, and the ice-fields coming up with it flanked it on either side, seeming at one moment like a plain, dotted with trees and animals; again, as rugged mountains, and then breaking up after awhile, disclosed a long line of bears, and dogs, and birds, men dancing in the air and skipping from the sea to the sky. There was no end to the forms which appeared every instant, melting into other shapes as suddenly. For hours we watched the insubstantial pageant,' until a wind from the north ruffled the sea, when, with its first breath, the whole scene melted away as quickly as the 'baseless fabric' of Prospero's vision." Scoresby, during a voyage to the eastern coast of Greenland, was amused by the singular refractive power of the Polar atmosphere. The rugged surface of the coast'assumed the form of castles, obelisks, and spires, which here and there were linked together, so as to present the appearance of an extensive city. At other times it resembled a forest of naked trees, and it was easy to conceive colossal statues, porticoes of rich and regular architecture, shapes of lions, bears, horses, &c. Ships were seen inverted, and 210 THE AURORA BOREALIS. suspended high in the air, and their hulls often so magnified as to resemble huge edifices. Objects really beneath the horizon were raised into view in a most extraordinary manner. It seems positively ascertained, that points on the Greenland shore, not above three or four thousand feet high, were seen at the distance of one hundred and sixty miles. The extensive evaporation of the melting ice, with the unequal condensation produced by streams of cold air, are considered as the chief sources of this extraordinary refraction. The same navigator 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, where her appearance 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 and their hulls meeting, according as the inverted image is above or below the other. "The most remarkable instance of mirage I have seen," says Dr. Kelly, "was that in which a vessel, with all sails set, at one moment looked like an immense black chest, no sails or masts being visible. On observing her for a time, the black body seemed to separate horizontally into two parts, and two sets of mingled sails occupied the intervening spaces, with one set of very small sails above. The figures afterwards became more distinct, and three images were clearly discerned. Another vessel changed, also, from the form of a great square flat-topped chest, to five distinct images, the upper with the sails erect, and the two lower double images with their sails rather confusedly intermingled." Another phenomenon which is seen in its highest perfection in the Polar seas is the Aurora Borealis, or the "Northern 'Daybreak," so named from its appearance in that part of the heavens, and its close resemblance to the aspect of the sky before sunrise. DESCRIPTION OF THE AURORA BOREALIS. 211 The lines of James Montgomery on this grand spectacle of nature are very fine: "Midnight hath told his hour; the moon, yet young, Hangs in the argent west, her bow unstrung; Larger and fairer, as her lustre fades, Sparkle the stars amidst the deepening shades: Like a new morn from Orient darkness, there As though from heaven's self-opening portals came And rabid Sirius foams through fire and blood. During the winter of the Northern Hemisphere, the inhabitants of the Arctic zone, as I have informed you, are without the light of the sun for months together, and their long dreary night is relieved by the light of this meteor, which occurs with great frequency in those regions, and the exceeding beauty of which those who have seen it only in our latitudes can hardly conceive. It is generally described as an immense curtain, waving its folds like the canopy of an ample tent agitated by the wind, and fringed with a border of light of the richest colours and most vivid brilliancy. It is sometimes seen for a few minutes only, or an hour, or through the whole night, and through several nights in succession. A dingy aspect of the sky in the direction of the north is gene 212 ELECTRICAL ORIGIN OF THE AURORA BOREALIS. rally the precursor of the Aurora, and this gradually becomes darker in colour, and assumes the form of a circular segment, surrounded by a luminous arch, and resting at each end on the horizon. Sometimes the blue sky is seen between the cloud and the horizon. After shooting a number of rays or streamers, the dark part of the cloud generally changes and becomes very luminous. The rays continue to be shot from the upper edge, sometimes at some distance, or very close to each other. Their light is very dazzling; bright columns slowly issue upwards from openings in the main cloud, becoming broader as they proceed. When the Aurora attains its full brightness and activity, rays are projected from every part of the arch, and if they do not rise too high, it presents the appearance of a comb furnished with teeth. When the rays are very bright, they assume a green, violet, purple, or rose-colour, giving to the whole a variegated and brilliant effect. The height of the Aurora has been differently estimated, but it has been seldom found to exceed ninety miles; but its geographical extent is enormous. The origin of the phenomenon is yet unexplained, but it is generally supposed to be electrical. Franklin regarded it as the result of a slow and continual discharge of electric fluid from the atmosphere about the poles to the air above; and Sir Humphrey Davy and other electricians noticed the striking similarity between the Northern Lights and electricity discharged through rarefied air. The Aurora has been observed in almost every part of the world. The ancients regarded its appearance with great terror, as the precursor of dire events; and there is no doubt that the fiery meteors, representing to their imaginations armies fighting in the heavens, and described by many writers as having preceded remarkable occurrences, must have been this phenomenon. The Indians also regarded these lights as the spirits of their fathers roaming through the land of souls. This idea may have originated from the long streaks of light which spread out with inconceivable swiftness, but always appearing to move to and from a fixed point, somewhat like a ribbon held in the hand and shaken. Other luminous meteors are seen by the navigators of the HALOS AND MOCK SUNS. 213 Northern Ocean to perfection, arising, apparently, from the refraction caused by the minute and highly crystallized particles of ice floating in the atmosphere. The sun and moon are often surrounded by Halos, circles of vapour, tinted with the brightest hues of the rainbow. Arctic voyagers frequently mention the fall of icy particles during a clear sky and a bright sun, so small as to be scarcely visible to the naked eye, and detected by their melting on the skin; and others larger, presenting a remarkably interesting appearance. M'Clintock, in his "Voyage of the Fox," observes: "The snow crystals of last night are extremely beautiful; the largest kind is an inch in length, and its form exactly resembles the end of a pointed feather. Stellar crystals, two-tenths of an inch in diameter, have also fallen; these have six points, and are the most exquisite things when seen under a microscope. In the sun, or even in moonlight, all these crystals glisten most brilliantly, and as our masts and rigging are abundantly covered with them, the 'Fox' was never so gorgeously arrayed as she now appears." Parhelia (from Greek words "near the sun "), or mock suns, in the vicinity of the real orb, shine at once in different quarters of the firmament. They are most brilliant at daybreak, diminish in lustre as the sun ascends, but again brighten at his setting. Sir Edward Parry describes a parhelion of remarkably gorgeous appearance which he saw during a winter's sojourn at Melville Island. It continued from noon until six in the evening. It consisted of one complete halo, with segments of several others, displaying in parts the colours of the rainbow. Besides these, there was another perfect ring, of a pale white colour, which went right round the sky parallel with the horizon, and at a distance from it equal to the sun's altitude, and a horizontal band of white light appeared passing through the sun. Where the band and the inner halo cut each other, there were two parhelia, and another close to the horizon, directly under the sun, which formed the most brilliant part of the spectacle, being exactly like the sun slightly obscured by a thin cloud at his rising or setting. A singular phenomenon observed on the Arctic seas by Mr. O'Reilly is mentioned in his account of Greenland. The atmo |