The Mirage.

Ashburton Guardian, Volume I, Issue 10, 18 October 1879, Page 4

The Mirage.

According to a paragraph in the “ Lancet,” a singular example of the optical illusion known as the mirage recently occurred at Tenby. A photographer happened to take a photograph of the church spire of that town ; whilst doing so he observed nothing extraordinary, but on the development of the plate there appeared across the spire the distinct outline of a boat with colors flying fore and aft. It was ascertained that exactly at the time the photograph was being taken, a gunboat was launched from the Pembroke Dock, exactly answering in appearance to the outline which so mysteriously appeared on the photographer’s plate. It is an undoubted scientific fact that where ' there happens, from any meteorological cause, to be a stratum of atmosphere of considerably higher power than that immediately below it, the upper stratum acts as a kind of mirror, and may reflect objects at a very considerable distance. The extraordinary instance of this phenomenon is the well-known case of Captain I Bcorcsby, who, whilst engaged in the whale fishery, obtained the distinct effigy of his father’s ship suspended in the air, and thus ascertained the fact, of which he had been previously unaware, that his father was in the same quarter of the globe as himself. The vessel in question turned out to have been 150 miles distant when its refracted imago was seen. In the hot countries of the south and east the mirage is frequently seen, and in the Straits of Messina it has acquired the name of the “ Fata Morgana,” from the ancient superstition of its fairy origin. It is, perhaps, a little doubtful whether, if we accept the apparently truthful account of travellers, the phenomenon of the mirage is entirely explained by the theory of refraction. Very frequently the incorporal but realistic visions of the air are evidently exact images of objects at a distance. But on the coast if Sicily, we are told, the phantoms often take the form of magnificent palaces, stupendous castles, and vast armies of men on foot or on hoiseback, objects which can scarcely be supposed to have their counterpart on the adjoining shores. Again, in the African desert, when the mirage appears in its most cruel form, and the exhausted traveller is cheated by the delicious image of distant groves and fountains, it seems at least likely that the illusion arises from a morbid and feverish condition of the retina of the observer, such as that which produces, for example, the frightful spectres of “ delirium tremens,” rather than from the refraction in the atmosphere of some actual oasis. In some cases, indeed, in which the mirage has been observed in the desert, the distance from any real oasis must have been immense.—“ Globe.”