POLAR PHENOMENA

Evening Post, Volume CVIII, Issue 148, 19 December 1929, Page 19

POLAR PHENOMENA

MIRAGES AND HALOS

EXTRAORDINARY EFFECTS

BEAUTY OF THE AURORA

Many strange sights -will be seen by the members of the Mawson Antarctic expedition ..when their vessel crosses the Antarctic Circle. The Polar air is full of phantoms, mirages, halos, queer: distortions of the sun and moon, and, •of course, the Aurora Australis. The sun is sometimes seen with three or more prismatic bands surrounding it Where these bands intersect one another' bright, glowing spots, called "mock suns," appear. ;The presence in Polar air of millions of tiny ice crystals is responsible for most of these strange distortions. These crystals, writes H. A. Davies, in the Melbourne "Argus," refract and reflect the light of the sun or moon, and produce the most extraordinary effects, often quite close to the observers. Sir Douglas Mawson, in his "Home of the BlizzaTd," mentions how he formed artificial halos close to his face, simply by breathing towards the moon. Of all the halo phenomena the mock suns (par'ahelia) and the mock moons (paraselenae) are the most admired. A remarkable paraselene was seen by the members of the Scott Antarctic expedition on 11th June, 1911. It was sketched by the late Dr. Wilson, who perished in 1913 on the return journey from the South Pole with Captain Scott. SCORBSBY'S OBSERVATIONS. _ The occurrence of optical phenomena in the Antarctic is aided by the fact that .the sun, when above the horizon, is generally at so low an angle that its light is sent through a long stretch of atmosphere. This also leads to intensely prolonged sunsets and dawns, the colours of which last for hours. Contrary to:.the general opinion the icy wastes are not monotonously white. The sky is remarkable for the richness and diversity of ita colours. The clouds at times are actually irrideseent. Mirages usually associated with tropical deserts are' just as common in the Polar regions. One of the earliest descriptions of_the Polar mirage was made by the British whaling captain, William bcoresby, in 1820. Scoresby, in addition to being a whaler, was also a scientist, ana he kept a careful record both written and pictorial, of his observations. The Fata Morgana, which greatly frightened the superstitious seamen, is thus described by him: "A light breeze having come from the Borth-west about 6 o'clock in the evenMg, a thin band of stratus cloud, or a f ogbank, at first much illuminated by the ?un, appeared in the same quarter. On this, most of the ships navigating at a distance of 10 or 15 miles and amountMg_ to 18 or 19 sail, began to change their, form and magnitude, and when examined by a telescope from the masthead of the Baffin, exhibited some extraordinary appearances, differing in effect at almost every point of the compass. One ship, bearing north-west by west, had a perfect image, as dark and'distinct as that of the original united to its masthead in an inverted position. Two others at north-wost presented two distinct inverted images in the air, one of them a perfect figure of.the original, the other wanting a hull. Two or three more, bearing about north, "were strangely distorted, their masts appearing at least twice their proper height. At the same time some

vessels bearing north-east and east exhibited aft appearance totally different from all the preceding. These, five in number, were at a. distance of 12 to 15 miles/ and considerably below the natural horizon, but owing to the in fluence of some peculiar vapour in the air they now seemad to advance so near that they became distinctly visible." ■ . . MIRAGE OF BATTLEMENTED CITY. On . another occasion Scoresby saw the cliffs; along the east coast of Greenland distorted by the .Fata Morgana. He wrote: "The general telescopic appearance of the coast was that of an extensive ancient city, abounding with the. ruins of castles, obelisks, churches, and monuments, with other large and: conspicuous buildings. Some of the hills seemed to be surmounted by turrets, battlements, spires, and pin--na'cles,- while others, subjected to two reflections, exhibited large masses of rock, apparently suspended in the air, at a considerable elevation above the actual-termination of the mountains to which they referred. Scarcely was any particular portion sketched before it changed its appearance, and assumed the form of an object entirely different. It was alternately a castlo, . a cathedral, or an obelisk; then, expanding horizontally and coalescing with the adjoining hills, united the intervening valleys, though some miles in width, by a bridge of. a single arch of the most magnificent appearance and extent." ■ - . An extraordinary mirage was observed by the officers- of, the. steamer Glena-mpy..-in March, 1928. Following the elevation of • distant islands, which ■ rendered -' them - visible at enormous distances, the masts and funnel of a steamer 'below thei horizon came into view. ■ As' theY officers watched' it 'a complete projection" of ' the steamer, deckhouses, arid hull being plainly visible, was seen above and astern of the steamer, apparently carried by the smoke. . ■ ■ . ANTARCTIC MIRAGES; - ; Scott's ■northern- party, under Lieutenant ..Campbell, noted on 15th Octoher, 1912;-J'TMs day we saw a wonderful mirage, the ridges of pressure ice to the southward being seen inverted against the sky." In Febriiary } 1912, two members of Scott's western geological party, under Professor Griffith Taylor (leader) and Lieutenant Gran, when climbing a,hill near ..Cape Bcrnacchi, saw a shipin a mirage. "It seemed clear to both of us," wrote Professor Griffiths Taylor, •'' even through binoculars—smoke, crosstrees,. hull, and three masts; but. after an hour or so we decided it was only a mirage." .■'.•.■ Lieutenant Campbell also no;tes a remarkable mirage in November, 1912. "It was a lovely morning, with a bright sun. -Soon after starting we' thought wo saw three men pulling a sledge. Priestly and I walked towards them. They apparently stopped. Priestly began semaphoring while I looked through my glasses, but there was no result. Suddenly they turned, and I saw that they were Emperor penguins miraged in such a way that made them look like men."

Mr. Louis Bernacchi, who Jed an Antarctic expedition in the years 1898----1900, also writes:—"A very line refraction effect became visible at midday. Huge icebergs to the north, which in ordinary circumstances were invisible even from, the huts, were elevated by refraction to a height on a level with the top of Cape Adare, the height of which is nearly 900 ft. The display was ever-changing in appearance. Sometimes one part of the horizon, was elevated, then this would subside and another part rise ■ up. " This type of'mirage, known as "looming," was probably responsible for the charting by Commander AVilkes in 1840 of part of the Antarctic continent in a position later sailed .over by Captain J. K. Davisf thus beginning

a controversy which has continued to the present day over the discoveries 'claimed' by Wilkes for- the "United States. Another mythical polar land, due probably to "looming," was Crocker Land, which Peary believed ho saw from. Jape Columbia, at the north of Greenland, in 1906. Macmillan travelled over its supposed position in : 1914,-and proved that it did not exist. :-,'.. HALOS AND MOCK SUNS. While oil the march towards the South Pole .on 15th November, 1911, (Scott makes :'.tho following remarks about an extraordinary sun halo: "As we marched, towards midnight the sky became overcast. Very beautiful halo rings formed around the sun. Pour 'separate riugswere very distinct. Wilson described a sixth. The orange colour- with blue interspace formed very fine contrasts.^: We .could clearly see thu corona ring on the snow surface." The most remarkable sun halo ever recorded was:seen and. sketched by Johannes Hevel . ;at Dautzig on 20th February, 1663, when no fewer than seven suns were, visible at the "arcs of contact, 1' or the - intersections of the various ;halo circles. Not infrequently mock suns are seen without the rings being observed. AW. Greeley, who was stationed at Fort Conger, Grinnell Land, in the Arctic regions,' mentions that solar halos of great-beauty frequently occurred. Dojible " halos with -four, 'five, or ■ six mock suns of great splendour were often seen.- At times these were observed against the background of a high hill less than a mile distant. Lunar coronas were ; als.o common. Coronasare caused by : the passage of light cirrus ..clouds or aqueous vapour before the; ni.ooh,;' thus, interfering with the rays of light as they pass by the drops of vapour.- \ : .". ,- '■;.■

The most fascinating atmospheric effect-seen in high latitudes, however, is the Aurora. Sir James Clark Ross gave a very convincing explanation by declaring that the Aurora is caused by the reflection of-the light of the sun from the polar icefields on to the clouds above, but modern research has decided that it is caused;-by. an electric discharge. The weird beauty and splendour of the Aurora.have been described by numerous writers, but those who have had the privilege of witnessing a, display state that-words are inadequate to convey its exquisite and ever-chang-ing beauty, .and that because of the constant changes, its effect cannot bo preserved .in a. picture. . The mystic light of the Aurora, glowing in the rarefied atmosphere scores of miles above the carth/s surface, conies and goes coincidently with the outbreaks and-subsidences; of storms in the sun. It is shaped and shifted to and fro under the influence, of-the invisible lines of magnetic force of the earth. Being the highest thing : within the earth's atmosphere; its spectrum furnishes scientists' with -valuable data of the constituents of the air at great altitudes. Numerous attempts were made by Mr. H. G. Ponting. the photographer of the Scott expedition, to obtain photographs.of the Aurora, but without success. Scott,describes, the Aurora in these words:—-"The auroral light is of a palish-green colour, but we now see distinctly a red flush preceding the motion -of any bright part. The green ghostly light ueems suddenly to spring to life with rosy- blushes. . There is infinite; suggestion in this phenomenon, and in this lies its charm; the suggestion of life, form, colour, and movement never less than evanescent, mysterious—no reality. It is the language of mystic signs and portents—the inspiration, of the' gods—wholly spiritual —divine, signalling. ■ Remindful of superstitution, provocative of imagination.- Might not the inhabitants of ■some other world (Mars) controlling miglity forces thus- surround our globe with fiery symbols', .a'golden writing which'"we :haver-.'Sip't" the key to der 'cipher??*''" '' ' '""..'.-■ J