Geology of Mount Sinai and adjacent Countries. 271 



ness during the other seasons of the year, since the sun would 

 then generally produce, from its intense heat, much mist and 

 haze. Indeed Wellsted states (p. 179), *' This extraordinary 

 clearness, or purity of the atmosphere, is mostly observed in 

 December, January, and February ; and during this period, 

 the outline of any object on the horizon, however distant or 

 small, may be seen with the utmost distinctness ; the brilliancy 

 of the nights is also very great," and affords to the sailor 

 facilities for navigating the gulfs. 



The second, or the Mirage, is very common ; and its vari- 

 ous appearances are occasioned by the refraction of light 

 through the lower strata of air of different density, caused 

 most frequently, in the arid desert, by heat. This illusion, 

 as is well known, presents to the traveller a phantom tract 

 of water, or a lake, often with an undulating surface, and is 

 called by the Arabs Serab, which word is of great antiquity, 

 for it occurs in Hebrew in Isaiah xxxv. 7, and is incorrectly 

 translated in our Bible, " the parched ground," instead of 

 " the Mirage,^"* or " mock water."* 



Of the other phenomena I need only mention the Simoom, 

 or hot wind of the desert, which brings with it a quantity of 

 fine sand, and penetrates through everything ; the air being 

 very hot, and perhaps laden with excess of electricity, every 

 animal is severely affected by parched mouth, difficulty of 

 breathing, fever, and other distressing symptoms. Rounded 

 or twisted columns of sand, whirlwinds, and showers of dust 

 or minute sand, carried on with the force of a hurricane, 

 sometimes produce vast destruction to man and beast. Allu- 

 sion is made to the sand-storm in Deuteronomy xxviii. 24, — 

 " The Lord shall make the rain of thy land powder and dust : 

 from heaven shall it come down upon thee, until thou be de- 

 stroyed." So Lucant : — 



*' At, non irabriferam cum torto pulvere nubem 

 In flexum violentus agit, pars plurima terrae 

 Tollitur, et numquam resoluto vertice pendet." 



* Confer Diodor. Sic, Lib. iii., p. 219.— TTeweZ. 



t Pharsal. Lib. xi., v. 463-7. And see the following verses for a farther 

 and excellent description of a sand-storm in the Libyan Desert. 



