In this example it is the hot air, radiating from a sunlit desert plain, that causes a Tunesian mountain to transform into a flying saucer.

[Still taken from Les mirages, Histoires de chimères et de la fée Morgane, a documentary film by Michael ENGLER, broadcast by Arte, on April 18 1998. Copies of this remarkable film can be purchased at : http://www.zdf-enterprises.de.]