Fata Morgana

Introduction

La Fata Morgana is the Italian name for Morgan Le Fay, the legendary sorceress best known for her role in the Arthurian stories. (One also encounters the French form of the name, Morgain la Fée.) Local folklore has for centuries held her responsible for the spectacular mirages seen in the Strait of Messina between Reggio di Calabria (Italy) and Messina (Sicily). Consequently, the name has been transferred to these mirages themselves, which are characterized by multiple and rapidly changing images, with vertical and horizontal features that suggest architectural structures.

But how did a character from Celtic folklore come to be associated with a mirage in southern Italy? Where do these strange names come from? And how are these complex displays actually formed?

It's all a rather long story, so here's an outline of this page, if you want to jump to a particular section:

Note that there are many boldfaced links to the bibliography, which are slow to load because of its length.

The names

The epithets Le Fay and La Fata both mean “the fairy”, a clear reference to her supposed supernatural powers. These terms are ultimately derived from Latin fata, fate.

The name “Morgan” may connect this mythical character with the sea, which is môr in Welsh — cf. mer in French, morye in Russian, etc. (In Geoffrey of Monmouth's account of her, one of her eight sisters was Morgause, Queen of the Orkney Islands; the story of nine priestesses with magical powers on an island goes back to Pomponius Mela, about 43 AD.) “Morgan” is also related to the Welsh “Modron”, derived from the Celtic mother-goddess Matrona, whose name survives today in the River Marne (another watery connection). All of these names seem to be related to the same character.

Much of the historical material on the early Morgan folklore is reviewed in a recent Master's Thesis by Dax D. Carver; the third chapter discusses the origin of the name, drawing heavily on the discussion in the first chapter of Lucy Paton's book (see below).

A much less plausible derivation of Morgana (from Hebrew or Greek) is offered by Minasi (and, quoting from him, Boccara).

The character

The origin of the character “Morgan Le Fay” is lost in early Celtic folklore. The early history is discussed by the Arthurian scholar R. S. Loomis in his article “Morgain la Fée in oral tradition” [Romania 80, 337-367 (1959)], which was reprinted in his posthumous collection of essays

Studies in Medieval Literature
(Burt Franklin, New York, 1970)
— which, itself, is partly available at Google Books. An earlier article along the same lines is Loomis's “Morgain la Fee and the Celtic Goddesses”, Speculum 20, 183–203 (1945).

Loomis argues that Morgan was already a well-established feature of Breton folklore and song as a water-nymph and goddess with magical powers, when she first appeared in written records about the middle of the 12th Century. (The Bretons were Celtic refugees from Britain who fled before the Anglo-Saxon invaders and settled in Brittany — now northern France — in the 5th and 6th Centuries.) He also connects Morgan with the Celtic Morrígan, the “washer at the ford”, who predicts the deaths of warriors, and (like Morgan) can appear as a black bird.

By the time Morgan was introduced into the story of King Arthur by Geoffrey of Monmouth about 1150 AD, the historical counterpart of the legendary Arthur had been dead for six centuries.

Morgan's connection with mirages can be traced back to the 13th-Century prose romance of Lancelot du Lac, in which “the Lady of the Lake … lived in a wooded country covered by a magical cloud which gave it the appearance of a lake” [according to K. M. Briggs in The Fairies in English Tradition and Literature (U. of Chicago Press, 1967), p. 4.] (The Lady of the Lake is another avatar of the Morgan character.) This “magical cloud” is probably the “fog” that is frequently (mis)perceived by inexperienced mirage-watchers in the zone where the superior mirage appears — i.e., Wegener's blank strip. Hurd aptly calls this appearance “mock fog”.

Interestingly, the Lake in Lancelot du Lac is called the Lake of Diana, the queen of Sicily. This provides an early glimpse of a Sicilian connection; but there are other connections between Diana and fairies in Italy. For example, the Neapolitan term janare for the fairies who produce mirages is derived from the Latin ianara, which refers to Iana or Diana, the Roman goddess of the hunt, the Moon, and nocturnal incantations. (Miss Paton has an Excursus pointing out the similarities between Diana and Morgain; to which one might add the shape-changes of both the fairy and the Moon.)

The legend of Morgan was elaborated further by Sir Thomas Malory in his posthumously published book Morte d'Arthur (1485) — though she played a rather minor part in his story.

Many other authors found Morgan an irresistible character, and embellished her story accordingly. In particular, she had an important role in Boiardo's epic poem “Orlando innamorato”, published in 1495, after Boiardo's death in December, 1494. There, Morgana is credited with using her mirage to distract Orlando (the Italian for Roland). As Boiardo spent his last years as governor of Reggio, he may have learned the folklore connection between the fairy Morgan(a) and mirages there.

Boiardo took most of his characters (but not Morgana) from the mid-12th-Century French Chanson de Roland (Song of Roland); Roland, a nephew of Charlemagne, was a real person who died in the Battle of Roncevaux Pass, in 778. When Boiardo died, leaving his epic incomplete, the story and characters were picked up by Ariosto, in his Orlando furioso. Morgana has a small part in this continuation.

These Roland epics mix Arthurian and Carolingian legends with pieces lifted from Classical Greek mythology, such as the sowing of the dragon's teeth in the story of Jason and the Golden Fleece. Other writers were still more eclectic in combining sources of inspiration; for example, the 13th-Century French epic of Huon de Bordeaux makes the dwarf Auberon (Shakespeare's fairy-king Oberon) the child of Morgan le Fay by Julius Caesar!

The various accounts of Morgan are quite inconsistent. In some, for example, she is Arthur's sister; in others, his half-sister; in still others, his cousin; elsewhere, no kinship is suggested. Similar contradictions abound throughout the stories — for example, any relationship with Arthur is incompatible with her supposed liaison with Caesar, who lived centuries before the historical Arthur. Thus, attempts (such as that by Carver) to construct a coherent biography of Morgan from the available material seem rather contrived and artificial. Indeed,

Edith Whitehurst Williams
Morgan La Fee as Trickster in Sir Gawain and the Green Knight
Folklore 96, 38–56 (1985)
argues that the inconsistencies and contradictions in Morgan's character are essential features of her “archetypal nature”.

Various tales concerning Morgan are reviewed at some length in the second, revised edition of Lucy Allen Paton's 1903 book:

Studies in the Fairy Mythology of Arthurian Romance
(Burt Franklin, 1960)
which contains some additions by Roger Loomis. (Again, parts of this book are available at Google Books.) While this standard reference is mainly devoted to Morgan, it concentrates on the Celtic folklore, and so is little help with the Sicilian connection.

The Sicilian connection

Fortunately, there is a fine work (in Italian) by the remarkable poet, scholar, critic, and folklorist Arturo Graf, who fills in this gap admirably:
Arturo Graf
Miti, Leggende e Superstizioni del Medio Evo
(Burt Franklin, New York, 1971)

This two-volume work, a facsimile reprint of the 1892/93 original (which, once again, is available at Google Books), covers several aspects of the Fata Morgana story. The first essay in the first volume deals with stories of the earthly Paradise, which includes a discussion of St. Brendan's island and other enchanted isles, such as Avalon — the “island of apples” — (where Morgan is said to have taken Arthur to be cured of his battle wounds, and from which the Bretons believed he would return to them some day). Near the end of the second volume is a study of the identification of this island with Sicily, and the transfer of Arthur's resting-place to that island — indeed, to the supposedly hollow interior of Mt. Etna. Graf traces this story back to the 12th Century.

Loomis gives a brief summary, as does Lucy Paton (on pp. 250–252 of her book). Apparently, the Breton legends about Arthur were carried to Sicily in the 11th Century by the Norman invaders of that island. Fertile Sicily, with its mild Mediterranean climate and citrus fruits, might well have seemed an earthly Paradise — the “island of apples” — to the invaders from chilly northern Europe, especially given that the Arthurian legends call it a place of eternal summer, where the trees bear fruit continually (as do figs and citrus). And an active volcano, Etna, would add to the magical flavor of the place. Once you identify it as Arthur's resting-place, you remember that Morgan is supposed to have brought him there. Then the shape-shifting attributed to Morgan fits nicely with the changes in appearance of the mirages; and their association with the Strait of Messina fits with Morgan's associations with water.

Much of this is speculation; but it does make a plausible argument, after the fact.

The mirages

The early observations

Agrippa and Josephus

No doubt the mirages in the Strait of Messina were noticed by the local inhabitants from very ancient times. Pernter & Exner devote a long section (pp. 163–188) to them, tracing the earliest written references to Cornelius Agrippa's De occulta philosophia libri tres (1531). (However, as Richard Westfall characterizes Agrippa as “a self-aggrandizing liar” we should take Agrippa's vague mention of mirages with a grain of salt; see also the Stanford website.) Agrippa's rather general description of “marching armies” are probably just a reference to such early observations as those of Flavius Josephus — whom he mentions a few pages earlier — rather than the classical Fata Morgana of southern Italy.
CAUTION: Agrippa's “marching armies” (and similar assertions by other observers about castles, towers, flocks of sheep and cattle, etc.) seen in mirages should not be taken literally. As I point out elsewhere, these are interpretations made by the observers, not actual things that were seen. Bear in mind that they are not the objects whose distorted images appeared in the mirages. (See the additional comments on these things later on this page.)

de Ferrariis

Italian mirages were described by Antonio de Ferrariis in his book De situ Japygiae, an account of the region now called Apulia, or Puglia (the heel and back of the ankle, in Italy's “boot”), on the Adriatic coast. He says that in the swamps around the Gulf of Taranto,

… certain apparitions are seen, which are called Mutationes or Mutata. The common people tell tales of I don't know what, vampires or witches or, as they say in Naples, janare [fairies], or as the Greeks say, nereids. …

And sometimes you will see cities and castles and towers, and sheep and different colored cattle and images or specters of other things, where there is no city, no sheep, not even a thorn bush. I myself have sometimes had the pleasure of seeing these plays, this lusus naturae.

They do not last long, but change as the vapors in which they appear, from one place to another, from one form to another, whence perhaps they are called Mutata, or because the sky is changed from sunny to rain by these apparitions.

(This was written about 1508, although his book was not published for another half century. This still makes his account the first by an eye-witness.) He also mentions apparitions of “armed troops arrayed for battle … in the sky”, and “likenesses of ships and sails, where there is no fleet.”

Facellus

A more specific reference was provided by Thomas Facellus (Tommaso Fazello) in his history of Sicily (De rebus Siculis decades duae, Palermo, 1558). Facellus, too, speaks in generalities, and does not provide details of any particular display; but he does associate his mirages with the sea between Calabria and Sicily:

In this same sea is seen yet another wonderful thing, which is that when the storm ceases, and the air becomes still, at dawn, changing images of animals, and of men, are seen in the air, some of which are quite motionless, some run through the air, some fight among themselves, and last even when the Sun gains strength, in whose heat all disappear.

Politi

The first mention of the name Fata Morgana for these mirages was made by Marc'Antonio Politi in his Cronica della Nobil'e fidelissima Città di Reggio (Messina, 1617), in which he says

… in the sea between the island of Sicily and Calabria … on a calm and bright day … particularly in the vapors of the morning which have lifted, are seen wonderful things; the air magnifies in such a way that it makes small things appear very large, and those far away become near, so that on these shores are seen new cities, infinite buildings, high towers, superb ports, and dense forests; and this vision the local people call the Fata Morgana, which they say shows her greatness, but the truth is that …
and he rambles off into arm-waving about the air being full of vapors when there is not a breath of wind. (But at least he realized that the air is the cause of it all.)

Kircher and Angelucci

The first circumstantial details about a Fata Morgana are given by Athanasius Kircher in his Ars Magna Lucis et Umbrae (1646), where (on p. 801) we find: Vocant autem Rhegini hoc spectaculum Morganam [The inhabitants of Reggio call this sight a Morgana]. Kircher was so interested that he actually travelled to Reggio in hopes of seeing a display, though he failed to do so. He therefore quoted from a letter from Father Ignazio Angelucci to Father Leone Sanzio, giving the details of an observation made on the morning of August 15, 1643 at the Strait of Messina. This seems to be the earliest actual account of the phenomenon in its nominal location:
On the fifteenth 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 is the Fata Morgana, which, for twenty-six years, I had thought a mere fable.
[This English translation was given by Henry Swinburne in his Travels in the two Sicilies (1783) — published just a decade after
Antonio Minasi
Dissertazione prima, sopra un fenomeno volgarmente detto Fata Morgana
(Roma, 1773),
on which the rest of Swinburne's account is evidently based.]

Minasi

Minasi himself had been an eye-witness of the Fata Morgana mirages three times. As the appearances were somewhat different each time, he divided the apparitions into three classes. He also had a copperplate engraving made to show what he had seen, which has been widely (though poorly) reproduced (e.g., by Boccara and by Pernter & Exner; although Gilbert refused to reprint it with his review of Minasi's work, saying that “it is indisputably a mere figment of the imagination and without any value”. Perhaps the best modern copy is the one published in Talman's review.) Minasi's account (and translations of it, such as Nicholson's) became the standard version of the story for the next century:

When the rising sun shines from that point whence its incident ray forms an angle of about forty-five degrees on the sea of Reggio, and the bright surface of the water in the bay is not disturbed either by the wind or the current, the spectator being placed on an eminence of the city, with his back to the sun and his face to the sea ;—on a sudden there appear in the water, as in a catoptric theatre, various multiplied objects ; that is to say, numberless series of pilasters, arches, castles well delineated, 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 and horseback, and many other strange images, 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.

As can be seen from this translated extract, Minasi couched his description in general terms, and failed to provide specific details of his actual observations. For this, and especially for his uncritical reporting of the more fantastic images as if they were factual, Minasi was harshly criticized by Ludwig Wilhelm Gilbert, the publisher and editor of Annalen der Physik, the leading physics journal of the 19th Century. Gilbert introduced his translation of William Nicholson's account of Minasi's work as follows: “As Minasi's daydreams have found favor with such a sober and sagacious physicist as Nicholson, I held it to be not without merit to demonstrate that Minasi's reports are mixed with so much imagination, that on the whole one can hardly take them for more than a fairy tale, and that as an attempt to explain the Fata Morgana, they should rather be set aside.”

The situation is not helped by the fact that Gilbert's treatment, in German, was based on Nicholson's rather loose English translation of Minasi's original Italian; and that later workers have garbled the translations still more. For example, the phrase translated by Nicholson as “alleys of trees” became “valleys of trees” in Brewster's 1830 Edinburgh Encyclopedia (and copies made from it); while Minasi himself merely refers to “very high trees” — no alleys or valleys. Careful workers will refer to the original, in such cases, and not rely on translations. Actually, Minasi's work is more credible than the later writers would lead one to believe.

Minasi's curious remark about the angle of 45° conflicts with Facellus's remark that the phenomenon appears at dawn; yet it has been widely reprinted. Likewise, his requirement for an elevated eye position is in conflict with the observations of Forel, and in any case is certainly not a necessary condition.

Minasi's work is a mixture of valid observations and irrelevant trivia. A useful feature of one of his sightings was that the miraged features were “all vividly colored, that is, fringed with red, green, blue, and purple.” These exaggerated effects of dispersion are only rarely seen in mirages of terrestrial objects, though they form the basis of green flashes. As we know from the sub-duct flash, this strong dispersion is visible only if the rays pass near the bottom of a duct.

In the same year that Minasi's dissertation was published (1773), Patrick Brydone produced an account of his visit to Messina, in which he describes the Fata Morgana — without, however, mentioning that name: he says the natives attribute it to the Devil. (So apparently the attribution to Morgana was not so widespread as other authors would have us believe.)

Giovene

A much more valuable observation was made a few years later by Giuseppe Maria Giovene, canon of the cathedral at Molfetta (on the Adriatic coast, about 300 km north of Messina.) Though his observation was not made at the classical location of the Fata Morgana, it is so similar to the previous descriptions — and so rich in circumstantial detail, which Minasi's account completely lacks — that it is worth quoting here. Note, however, that this is translated from a German translation of the original Italian — largely because that version is more compact and readable than Giovene's rather rambling original. [The German version contains some errors, which I have corrected in my translation below.]

I found myself on the 9th of February 1790 at a small country house, where I was especially glad to stay because of the open horizon. The days before had been clear, and a fairly strong northwest wind had blown. The exceptionally beautiful winter evening held me about half an hour after sundown at a window that opened directly to the SSW. The air was so still that the smoke from the towns Terlizzi, Ruvo, and Corato, of which I had a view, did not move at all, but hung over these towns like a great umbrella. When I looked around the horizon, it seemed to me that some clouds were rising at the extreme end of it, toward the west, which took in about 20 degrees. To be able to judge from this the wind, and the weather of the following day, I wanted to observe their course. They soon climbed to 2° height, but then began to take on manifold forms, and this display convinced me that they were something quite different from clouds.

I therefore asked Dr. Tripaldi, a very educated man, who was just visiting me for a few days, to take part in the further observations, and we both prepared ourselves for this most carefully. The supposed clouds took on a different shape every moment. First we saw in the background a lot of palaces and towers, which represented a great city, so that we believed we were seeing parts of Cerignola by means of a greatly increased atmospheric refraction; it lay in that direction, but more than 8 German miles [about 60 km], (in a straight line only 6 [i.e., 45 km]) away. Only the spectacle soon changed: we saw two hills next to each other, which became higher and higher, and then changed into rectangular towers with great windows, through which the evening twilight shone. But I cannot possibly describe all the different figures that took turns with the greatest rapidity.

Our astonishment, however, was soon greatly increased. The twilight was very bright, and I saw different times beams of light ascend from the extreme horizon up to a height of 6 or 7°. At first I took this for an illusion, only Dr. Tripaldi saw it exactly as I did, and the instant in which we perceived a new light beam agreed completely each time. We placed ourselves before the one window that faced directly WNW, and saw the phenomenon likewise. The light-waves went straight to the limits of the twilight; where the the twilight was stronger, they were more lively, and toward the limits of the twilight, weaker. Five or six light beams appeared immediately after another, then there followed a pause of one or two minutes, whereupon new beams showed, and during this display an infinite multiplicity of the strangest figures alternated at the extreme edge of the horizon. This beautiful spectacle lasted about half an hour; its beauty faded, as the twilight decreased, and after 3/4 hour was entirely gone.

Giovene makes an interesting comment about his local mirages: “The seamen of Molfetta call it Lavandaja — why, I know not”. But of course Lavandaja is Italian for “washer-woman”; so this is obviously a reference to one of Morgan Le Fay's avatars, the “washer at the ford”. In other words, just another name for Fata Morgana.

He has some useful comments about these mirages:

The Lavandaja appears in its greatest beauty if the wind has blown for a long time and now a calm succeeds it. It is commoner in fall and winter than in the remaining seasons, although one often sees it in summer and sometimes in spring. In summer we have almost every day a kind of small Lavandaja in the afternoons; but here, too, it is prettiest before sunrise and after sunset.

In Molfetta, one frequently sees the Lavandaja over Monte Gargano, a mountain that rises from the sea about 60 Italian miles away. It appears from there to the extreme horizon between WNW and NNW like a dark-blue cloud … . The first time I saw the Lavandaja there, without having heard of it, I became really uneasy. The whole mountain was in a trembling motion; one part of the mountain collapsed, and left behind a great valley; at the same place, a few minutes later, a new mountain arose, higher than before; and next to this climbed up several others, cone-shaped, but immediately assumed the form of great rectangular towers, which likewise collapsed in a moment and opened great valleys. Finally the whole mountain seemed to me to suffer frightful tremblings. — I have often observed these changes with the greatest enjoyment. The most wonderful figures follow each other in a moment, and an only somewhat warm fantasy would persuade you to see horses, men, ships, towers and cities.

The modern work

Boccara and Costanzo

The classical Fata Morgana mirages were reviewed extensively in 1902 by Boccara, who claimed to have read everything published on the subject. His paper is in Italian; but a French translation appeared the next year. Both versions contain a copy of Minasi's rather implausible discussion of the etymology of the term, attempting to derive it from Greek or Hebrew, and a large bibliography that reviews all the observations up to 1902.

Boccara believed that the Fata Morgana images were erect, and therefore not mirages; so his arm-waving explanations of the images are physically weak, and should be ignored. The main value of his paper is its review of the earlier literature.

The next year, Costanzo published a similar review of the Fata Morgana literature (also in Italian). His paper contains some references that Boccara missed, including unpublished letters and several items from local newspapers, with extensive quotations. There is a very useful summary table of the various observations.

Together, these two references are probably still the definitive work on the mirages observed in the Strait of Messina.

Forel and the Dufours

In the 1850s, similar mirage phenomena began to be noticed on Lake Geneva by the brothers Charles and Louis Dufour. Refraction phenomena on Lake Geneva were studied in a series of articles by F. A. Forel in the 1890s. He summarized this early work in his great limnological monograph Le Léman (1895), and continued his study of lake mirages into the early 20th Century, culminating with a paper in Comptes Rendus in 1911. The next year he gave an invited talk on this work in Edinburgh, which summarized his work on the Fata Morgana in a form accessible to English-speaking readers.

Forel's view, which is nicely summarized in a more recent paper by Helen Sawyer Hogg, is that the Fata Morgana occurs in the transition between inferior and superior mirages, when both conditions occur together. This would amount to a duct, enhanced by the additional effect of an inferior mirage below it. (Such combinations actually do occur over water; the Vatican photographs show many instances of both inferior and mock mirages, for example.)

Forel introduced the term “Fata Brumosa” or “foggy fairy” for a nebulous appearance often associated with these displays; one should beware of ignorant copyists who turn “Brumosa” into “Bromosa”. Both his observations, and those of the classical authors such as Angelucci and Minasi, show that ducting is essential for these complex mirages. Forel's observations at Lake Geneva were extended in the late 1920s by Bonnelance, who gives a clear description and classification of mirage phenomena.

The fantastic stories

Diodorus Siculus and Richard R. Madden

I've mentioned some of the more reliable observations of the Fata Morgana, concentrating on those from its “type” location, the Strait of Messina. Now, let's have a quick look at some less-plausible reports. We've already noted the claims, going back to antiquity, of animated figures. Let's add the observations of Diodorus Siculus, made in northern Africa (ca. 30 BC):
… at certain times, and especially when there is no wind, shapes are seen gathering in the sky which assume the forms of animals of every kind; and some of these remain fixed, but others begin to move, sometimes retreating before a man and at other times pursuing him, and in every case, since they are of monstrous size, they strike such as have never experienced them with wondrous dismay and terror. … although the natives, who have often met with such things, pay no attention to the phenomenon.

There are several things to notice here. First, the occurrence of these mirages “especially when there is no wind” — which allows strong thermal inversions to persist — is a legitimate observation, frequently made by those who see superior mirages.

Second, the difference in reaction to the phenomena by the tourist (Diodorus, here) and the locals: mirages are often made much of by tourists, and scoffed at by the natives. A more modern example is that recorded by Madden (1830), who thought that

At one moment, the rippled surface of a lake was before my eyes; at another time, a thick plantation appeared on either side of me; the waving of the branches was to be seen, and this view was only changed for that of a distant glimpse of a city; the mosques and minarets were distinct, and several times I asked my Bedouins if that were not Suez before us; but they laughed and said it was all sand; and what appeared to me a city, a forest, or a lake, the nearer I endeavoured to approach it the farther it seemed to recede, till at last it vanished altogether, ‘like the baseless fabric of a vision, leaving not a wreck behind.’
Madden noted that “it was more a mental hallucination than a deception of the sight; for, although I was aware of the existence of the Mirage, I could not prevail on myself to believe that the images which were painted on my retina were only reflected, like those in a dream, from the imagination, and yet so it was.”

And, finally, a Sicilian connection: Diodorus was a native of Sicily, as the epithet “Siculus” indicates.

Pliny and Flavius Josephus

Another classical report is that of Pliny, who claimed that
In the third consulship of Marius the inhabitants of Ameria and Tuder saw the spectacle of heavenly armies advancing from the East and the West to meet in battle, those from the West being routed.
This theme of armies marching in the sky is a common one in Fata Morgana reports. Shortly after Pliny, we have Flavius Josephus (78 A.D.):
… before sun-setting, chariots and troops of soldiers in their armour were seen running about among the clouds, and surrounding of cities.

de Ferrariis

Both Pliny and Josephus refer to “armies” seen in the sky, by people who had recently been involved in wars. Here's a similar example from more modern times: a few years after the sack of Otranto by the Turks in 1480, de Ferrariis says:
It is not long since the whole coast, from Otranto to Monte Gargano, at one and the same hour before sunrise, saw a fleet sailing from the east. It was thought to have been that of the Turks, and before that specter or delusion was revealed by the lightening dawn, various letters were composed here and there and messengers were sent concerning the approach of this imposing fleet.

(Notice that this is the same stretch of the Italian coastline where Giovene made his observations.)

the New Haven ghost ship

An American example is the “New Haven ghost ship”, a complex mirage display seen in 1648. According to John Winthrop:
There appeared over the harbor at New Haven, in the evening, the form of the keel of a ship with three masts, to which were suddenly added all the tackling and sails, and presently after, upon the top of the poop, a man standing with one hand akimbo under his left side, and in his right hand a sword stretched out toward the sea. Then from the side of the ship which was toward the town arose a great smoke, which covered all the ship, and in that smoke she vanished away; but some saw her keel sink into the water. This was seen by many, men and women, and it continued about a quarter of an hour.
(This was seen about two years after the colony lost a ship it had sent to England for supplies, on which great hopes had been laid.)

Irish mirages

In the 19th Century, there are many Fata Morgana reports from Ireland — typically embellished with fanciful details. The similarity of the Irish reports to the classical Fata Morgana of Messina and Reggio was pointed out by William Beauford (1802); I have quoted some of his accounts in detail elsewhere. He also noted a resemblance to “St. Brendan's island”, and other reports.

Of course, the accounts become amplified by repetition, so that the most implausible versions are those that come from “a friend of a friend” rather than directly from an eye-witness. Some of Beauford's stories are of this kind. Another example is found in

Anne Plumptre
Narrative of a Residence in Ireland during the Summer of 1814, and that of 1815
(Henry Colburn, London, 1817).

On pp. 123–124, she tells of encountering a clergyman, with whom

… I had a great deal of conversation on that extraordinary catoptric phænomenon the Fata Morgana, which is occasionally seen on this coast as well as the Straits of Reggio, to which it is so often compared. He said that he could not boast himself of ever having seen this beautiful delusion, but he had talked with persons of great credibility by whom it had been witnessed. It was in summer evenings, when the clouds appeared remarkably electric; appearances then exactly resembling castles, ruins, tall spires, groves of trees, rocks, and other terrestrial objects seemed to sail rapidly along the surface of the sea from the east to the west, remaining for a length of time sufficient to give assurance that such appearances actually existed, that they were not the mere effect of strong imagination;—at sunset they wholly disappeared. … In 1748 a book was published by a gentleman residing near the Giants' Causeway, in which a curious detail is given of an enchanted island seen annually floating along the coast of Antrim, of which it is said a sod thrown on it from the terra-firma would fix it for ever. Attempts have been made at various times to throw this sod, but hitherto all have proved abortive. At Rathlin a belief prevails that a green island rises every seventh year out of the sea between their island and the promontory of Bengore. The inhabitants assert that many of them have distinctly seen it, and that it is crowded with people selling yarn and engaged in various other occupations common to a fair.

Selling yarn, indeed! Well, that yarn seems to have sold well. (This one, too, is available at Google Books.)

Similarly, Cotton Mather's version of the New Haven ghost ship is considerably embellished from the original. Many other examples could be cited — mostly from the 19th Century, when it was uncommon for people with imperfect vision to wear eyeglasses. (People with blurry vision often use their imagination to supply the missing details.) But even in the early 19th Century, the pioneering mirage researcher H. W. Brandes remarked that “one would certainly arrive at an explanation through [instrumental] observations, rather than through the description of fairy-castles and other splendors, which certainly were seen only by the imagination and not the eye.”

The main cause of all these unrealistic claims is that the mirage observers, realizing that they are seeing something terrestrial, rush on to interpret the highly-distorted images as undistorted images of something familiar. Perhaps they are afraid to admit that they don't know what it is they're seeing.

It reminds me of Carl Sagan's remark about UFO's: “I have no objection to people seeing unidentified flying objects. It's when they start identifying them that I have problems.”

The missing photographs

Perhaps the most remarkable feature of the Fata Morgana, given all its attention in print, is the lack of photographs of it — especially from its classical location, in the Strait of Messina. This may be explained by Admiral Smyth's remark from 1854 that the Fata Morgana

is said to occur in sultry, calm weather, when the tides, or streamed-up waters, are at their highest, and when the sun shines from that point whence its incident rays form an angle of about 45° on the water. At such times, they tell us, multiplied images of all the objects existing on the two lines of coast — as castles, arches, towers, houses, trees, animals, and mountains — are presented in the air with wonderful precision and magnificence. Padre Minasi assures us that, in addition to obvious appearances, numberless series of pilasters, superb palaces with balconies, armies of men on foot and horseback, and many other strange figures, are seen in their natural colours and proper action, as in a catoptric theatre; and there exist paintings and engravings of the wonderful phenomenon. Still, on the whole, I cannot but repeat the conviction to which inquiry led me, and which I published as far back as 1824 (Sicily and its Islands, page 109): — “I much doubt, however, the accuracy of the descriptions I have heard and read, as I cannot help thinking that the imagination strongly assists these dioptric appearances, having never met with a Sicilian who had actually seen anything more than the loom or mirage, consequent on a peculiar state of the atmosphere; but which, I must say, I have here observed many times to be unusually strong.”

So it's possible that good photographs haven't been published because even the best ones don't support the wild claims of some visual observers. Even a good photograph of a real mirage is insipid compared to the fantasies of imaginative mirage-watchers. Mirages tend to be blurry, low-contrast objects; as James Gordon wrote, “Mirages are definitely not photogenic.”

But mirages aren't all that difficult to photograph, either. They're much easier to catch on film than green flashes, which are both considerably harder to photograph, and harder to observe at all: green flashes last just a second or two, while mirages are usually visible for tens of minutes at least. The most difficult photographic problem with green flashes is getting the exposure right: if the disk of the Sun is correctly exposed, the flash is usually underexposed; but if the sky is correctly exposed, the flash is usually overexposed. But mirages will be reasonably well exposed if the normal landscape exposure for the existing lighting condition is used. The main requirement is a camera with a telephoto lens.

The real photographs

In fact, photographs of mirages have been published for more than a century now; some early examples are R. W. Wood's 1898 photograph of an inferior mirage on San Francisco sidewalks, Wilhelm Hillers's 1913 picture of a mural mirage, and Vaupel's photographs (1926) of superior mirages in the Alps.

Indeed, there are a few mirage photographs that show some of the features reported by visual observers of Fata Morganas — notably, multiple images, extreme vertical elongation, and the pseudo-architectural alternation of horizontal and vertical features that suggests large buildings.

For example, a mirage seen in Penglai, China on May 7, 2005, had the architectural appearance of multi-story buildings. The upper, telephoto image on that page shows the mock fog in which the mirage was embedded; this atmospheric opacity is due to the looming and consequent large visual range produced by the duct. The second picture on that page shows, in a photograph taken with a normal focal-length lens, how narrow the blank strip that contained the mirage actually was. (Given the small angular extent, the claims of “bustling cars as well as crowds of people all clearly visible” made in the newspapers are hardly credible.) Additional images show the patchy structure of the mirage, poorly shown on the latter image, in more detail; while a Dutch website compares the mirage with the normal appearance of the area. (Note the hazy surface layer in the latter image.)

The Chinese mirage was seen over a bay, so the situation was similar to the Strait of Messina, or Lake Geneva. But complex mirages are also seen over land, if the situation favors strong thermal inversions. Of course, the best examples come from the polar regions, where the high thermal emissivity and low absorption of ice in the visible spectrum produce strong radiative inversions. A well-known example that shows extreme vertical stretching is Plates 7–4 to 7–7 in Greenler's book, showing mirages seen over the frozen Arctic Ocean from Point Barrow, Alaska.


To show that the Antarctic does as well as the Arctic, here are some images taken at McMurdo Station on Ross Island in 2004 by Rutgers University meteorologist Alan Robock. who has kindly made some of his pictures available for use as illustrations. For orientation, here's a general view across the frozen Ross Ice Shelf, showing the normal appearance of the southwestern skyline, as seen from a height of about 30 meters:
view of the southern horizon from McMurdo The largest mountain, a little to the right of center, is Mt. Discovery, about 2680 meters high and 64 km from the camera. (A rough calculation gives 2°10′ for its angular height.) The lower set of hills on the left belong to Black Island, about 38 km away; its highest point, Mt. Aurora, is 1040 m high. (That should be about 1°25′ above the astronomical horizon.) The apparent horizon between the two, in the middle of the image, is formed by distant hills and ridges beyond them — Minna Bluff, about 70 km away, and perhaps some more distant mountains.

Now here are two views taken at 3× larger scale on Oct. 1, 2004, when a duct was present. First, the appearance of Black Island: mirage of Black Island The mirage is evident just above the gray band, which may be partly mock fog, though it's too wide (almost 2° high) to be Wegener's blank strip. (Note: the green building here is different from the one in the picture above. To see how the two are related, look at another of Alan Robock's pictures, looking toward McMurdo from out there on the ice shelf.)

A few seconds later, he took the next image, which shows the area of Mt. Discovery, just to the right of the previous image: mirage of Mt. Discovery The mirage is most visible near the left edge, where this image overlaps the previous one; but if you follow it along horizontally, you can see the miraging in that same zone parallel to the horizon all across the picture.

There's nothing in the landscape to give you a sense of scale here. The lines in the snow are roads (vehicle tracks). The camera is about 30 m above the frozen Ross Ice Shelf. The ice cloud hides the pack ice at a distance of a few kilometers, much closer than the mountains seen above it.

Now let's zoom in and look at some of the mirage features more closely. First, here are some details from the region of overlap of the two previous pictures, plus a third picture that Alan Robock took. This area of the pictures has very low contrast, because of the atmospheric extinction and scattering in front of the miraged peaks. So I've enhanced the contrast by expanding the range of values: what was originally 100 out of 255 has been pulled down to zero, and what was originally 200 has been raised to 255, with linear interpolation in between. This increased both the contrast and the color saturation by about a factor of 2.5; so the colors look a little artificial.
mirage at 16:12:53


 
Time: 16:12:53
mirage at 16:13:48


 
Time: 16:13:48
mirage at 16:14:45


 
Time: 16:14:45
The first two pictures are separated by only 55 seconds of time; the second and third, by 57 sec. Even in less than a minute, you can see changes in the mirage structure. Just to the right of center in these panels, you see a 3-image mirage turning into a 5-image mirage, at the boundary between the whitish sky left of center and the dark rock to its right. Remember that erect and inverted images alternate, so the needle-like dark horizontal spike that develops (between the inverted image of the mountain slope and the erect image below it) is itself a double image of that same slope. (Such horizontal projections seem to have inspired their mis-identification as “balconies” by the Italians.) These rapid changes and multiple images are characteristic of Fata Morganas.

FM structure at Black Island But we don't see much of the exaggerated vertical magnification here that's also typical. However, that's visible elsewhere in the pictures. For example, here's the miraged zone in front of Black Island, shown with the same scale and contrast enhancement used above. The palisade-like vertical striations are fairly prominent. And there are some horizontal features as well; perhaps an imaginative eye might take the row of dark little dots near the middle of the miraged strip for windows in a long building.

FM structure at Mt. Discovery Then, in front of Mt. Discovery, we see some similar features (again at the same scale and enhancement). Once again there is a mixture of horizontal and vertical structures, though the combined effect is less architectural. Here, the vertical stripes are less pronounced, and the horizontal ones more prominent.

Notice how the forms in the mirages depend on distance. At 38 km (Black Island), there's strong vertical structure and a resemblance to architecture. At about 60 km (the near slope of Mt. Discovery), the structure is more horizontal. And at 70 km, we have a more standard 3-image mirage (though with another pair of images emerging in less than two minutes). I'll explain this regularity below.

Bigger versions of some of Alan Robock's pictures are available from his page of thumbnails; click on them to see the big versions.


But these phenomena are not confined to high latitudes. Look at Mila Zinkova's GIF animation of a mirage sequence photographed over Monterey Bay. Again there's rapid evolution (over a period of 33 minutes), as a 3-image mirage becomes a 5-image mirage, with the characteristic vertical exaggeration of the Fata Morgana.

Better yet, Mila has captured a real-time video of a classical Fata Morgana display near San Francisco.

Though there are dozens of photographs of green flashes on the Web, only a moderate number of decent mirage images exist. With the proliferation of digital cameras these days, you'd expect to see hundreds of images of mirages — including many of the Fata Morgana. And, surely, you'd expect to see some from the Strait of Messina, if all the stories about them were true.

The plain truth

Given the absence of photographic evidence for the more lurid visual reports, in spite of the ease of mirage photography, the only reasonable conclusion is that the stories are not true. Mirages seem to be Nature's Rorschach test: people read into them things that are not there — things that exist only in the minds of imaginative and suggestible people. People “see” things in mirages, just as they “see” things in clouds; remember the conversation between Hamlet and Polonius?
Ham.: Do you see yonder cloud that's almost in shape of a camel?
Pol.:   By the mass, and 'tis like a camel, indeed.
Ham.: Methinks it is like a weasel.
Pol.:   It is backed like a weasel.
Ham.: Or like a whale?
Pol.:   Very like a whale.
Hamlet, Act III, Scene 2
So the same vague shape can be read as a variety of different things.

But nobody supposes the things seen in clouds are real. It's just the ones perceived in mirages that get taken literally. Probably that's because clouds are clearly atmospheric; but mirages appear so close to the horizon that observers are tempted to (mis-)identify them with familiar terrestrial objects.

“Lateral mirage”

One of the side-effects of hasty identification is that the mis-identified objects are often in a different compass direction (azimuth) from the observer than the mirage. This has led to much nonsense about “lateral mirages” — in the sense of large angular displacements along the horizon. Atmospheric refraction doesn't work that way. The multiple images in mirages are always stacked up vertically; appreciable displacements horizontally just don't occur over level surfaces. (Tiny angular displacements, on the order of a few seconds of arc — much too small to be perceived by the naked eye — have been measured where the ground is steeply inclined, as in mountainous areas.)

Such identification errors may have many causes. First, the mirage distorts images, stretching or compressing them vertically; so a stretched image of a low hill may resemble the shape of a tall mountain in another direction. Second, looming may bring into view distant objects that are not normally seen, but whose miraged images resemble familiar nearby features at a different azimuth from the observer. In Fata Morganas, the distortions are so severe that the miraged object usually cannot be recognized at all from its image; at best, color may serve as a clue. The observer desperate to identify a feature in the mirage then names something familiar, regardless of its azimuth.

There is another kind of misidentification in complex mirages that has sometimes led to claims of multiple images displaced sideways from one another. This goes a step beyond the simple error of identifying some feature of the mirage as a known object: the observer thinks that several features in the display are images of the same object. All that is needed is two or more similar features. Well, whatever part of the landscape supplies the miraged objects, there are likely to be repeated instances of shrubs of about the same size and color, or rock outcroppings of similar color; when these are distorted into “forests” or “castles” or whatever, there may well be several of them of similar appearance. But mere similarity, especially in the low-contrast, indistinct images of mirages, is hardly adequate reason to assert identity.

Unfortunately, a number of influential authors have fallen into these errors. Among them I should point out Pernter and Exner, the old (1972) edition of the Meteorological Glossary, and the Smithsonian Institution's publication of James Gordon's credulous mirage report. These examples are even more inexcusable for having appeared well after Forel's thorough refutation (in pp. 561 – 565 of his 1895 monograph) of Soret and Jurine's infamous report.

Needless to say, there are no photographs that support the wild claims of “lateral mirages” displaced by many degrees.

Mural vs. lateral mirage
When vertical walls are the cause of a mirage, as in Wilhelm Hillers's mural mirages, the angular displacements are a few minutes of arc, not tens of degrees. These, too, are sometimes called “lateral mirages”; but in view of the wholly fallacious claims of large azimuthal displacements in Fata Morgana displays, I think it is preferable to call mirages produced by sunlit walls “mural mirages”, and discard the misleading term “lateral mirage”.

Explanations

Some of the mis-identifications are easily explained:

Aqueducts

Superior mirages require the observer to be in a duct; the top of Wegener's blank strip often caps a zone of inverted images with a horizontal line, above which sky (or distant mountains) can be seen. The inverted images of valleys in a miraged landscape then appear to be arches; the combination is interpreted as a Roman aqueduct (as in Angelucci's account).

Architecture

Likewise, alternating zones of vertical compression and extension of the image lead to architectural illusions, such as buildings with rows of windows. Vertically exaggerated images of isolated hilltops become “towers” or “steeples” — cf. Angelucci and Politi, or Giovene's “rectangular towers”. Vertically exaggerated shrubbery becomes a forest; etc.

Vertical stretching

The large vertical magnification seems likely to be produced by a strong thermal inversion above the observer; this is the mechanism Alfred Wegener described for superior mirages in his 1918 paper. Here the inversion acts like a concave mirror, producing great vertical magnification of objects beyond the horizon. If the inversion is entirely above the observer's head, everything on the ground out to the horizon can look perfectly normal. The miraged image then often looks like a wall made of vertical pilings or boards.

Effect of distance

If we regard the atmosphere as a lens, the greatest vertical magnification appears when the object and observer occupy conjugates of the lens, so that a point on the object appears to fill the lens aperture. If this is the condition required to produce a Fata Morgana display, it would explain why these are relatively rare: there's almost never an object at the point conjugate to the observer. Usually, things in the landscape are either closer to you or father away.

When the object is much closer than the focal length of the lens, there is little distortion — indeed, there is no mirage at all. When the object is 4 focal lengths away, we have maximum vertical magnification and a Fata Morgana. When the object is many focal lengths away, we see a real, inverted image between us and the lens; this is the inverted middle image of the 3-image mirage. These considerations explain the distance effect noted above. (To understand such effects in superior mirages, see the simulation pages, especially those that show distance effects in detail for Wegener's toy model, the zigzag-profile model, and a more realistic model.)

This effect may help explain why these displays are associated with the Strait of Messina. The strait tapers to a width of a few kilometers at the north end, while an observer on either shore can see stretches of the opposite coast at a considerable range of distances. When there is a duct, some part of the opposite shore is likely to be at the right distance from the eye to appear at this conjugate geometry, making the characteristic Fata Morgana features visible. (Similar considerations probably apply at Lake Geneva.)

Motions

The motions of internal details, which give the appearance of moving animals and men, have a different origin. Mirages produced by strong thermal inversions usually have waves that propagate along those inversions; these “gravity waves” are analogous to the waves on water, because they depend on the difference in density of two layers of fluid. In addition, there can be modulations of the mirage details by turbulent fluctuations carried by the breeze. As a result, details in the mirage appear to move more or less coherently from left to right, or from right to left, eliciting an illusion of a marching army, flocks of sheep, or herds of cattle.

Finally, as what is seen depends sensitively on the height of the eye, relative to the thermal inversion that produces the mirage, small changes in the depth and thermal structure of the inversion will cause the display to change its character within minutes, or to vanish suddenly. If the focal length of the atmospheric lens changes, different features of the landscape will appear magnified in turn, which again helps explain the rapidity of changes in appearance.

 

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