CHAPTER XXIX

190. 27 ff. Illusion cruelle! . . . This is the phenomenon frequently observed in t lie désert and known undei the spécial name of "mirage." Owing to an optical illusion, due to excessive bending of light rays in traversing adjacent Lavera of air of widely différent densities, displaccd or inverted images are produced. The mirage of the désert présents an appearance of objects reflected in a surface of water. Ollur phenomena, likc "looming " and cspecially the " Fata Morgana," observable in the sca bctween Sicily and Calabria, are of the same specics. The latter is regarded as the work of thc fairy Morgana.

191. 7-8. se lava la figure et les mains avec la poudre du désert. See note in page t68, line 20, and foll.

192. 11. l'ange Izrafil, or Israfil. Thc archangel of music. His voice is more melodious than that of any créature. He is to sound the résurrection trumpel of the last day.