The Optical Delusions Of Morgan le Fay The process of refraction, the bending of light rays as they pass through a thermally non-homogeneous atmosphere, can have fantastic consequences....

It is also responsible for the fata morgana, a rare optical illusion sometimes seen in southern Europe, and particularly common in the Straits of Messina that separate Sicily from the Italian mainland.

Morgana was a witchlike creature who appears in many guises in European folklore. In Irish mythology she was Morrigan, the Celtic goddess of death and destruction who embodied all that was perverse and horrible in the paranormal; she was capable of assuming many shapes, and on more than one occasion tried to tempt Cuchulainn from the task in hand by assuming a seductive role.

In the Arthurian legends, Morgan le Fay is Arthur's fairy sister, she who first whispered to the king about the goings-on of Lancelot and Guinevere.

She gave the king a magic draught, and no sooner had he drunk it than his eyes were opened to the truth and he saw the perfidious pair for what they were.

But it is in The Song of Rowland that we find Morgana's link with meteorology. Rowland was the bravest and most chivalrous of all the knights of Charlemagne.

Once upon a time, aware that Morgana held some fellow knights as prisoners in her magic castle, Rowland came upon the lady sleeping by a fountain.

He knew the only way to outwit her was to seize her by the hair, and he was about to do so when "all of a sudden he saw an array of towers, pinnacles and columns, palaces with balconies and windows, extended alleyways with trees, in short a scene of architectural magnificence surpassing all he had ever seen before.

While he stood gazing in silent astonishment, the scene slowly melted away and disappeared" - and of course, poor Rowland missed his opportunity.

It was because of this magic talent of Morgana - that she could, as it were, build castles in the air - that one of the rarest of optical illusions bears her name. Fata Morgana occurs when an unusual thermal structure in the atmosphere causes images of boats and buildings in the far distance to appear in the sky, and to be elongated in such a way that they seem like towers of great vertical extent.

The Fata Morgana can transform a distant nondescript horizon into an entrancing scene from fairyland, and it is said to induce in those who see it a deep sense of endless longing, tinged with blissful happiness.