GEOLOGY. 669 



breath, and even the sand attains an extreme heat ; my 

 thermometers being broken, I tried to ascertain the temper- 

 ature by plunging my hands into the superficial layers, but 

 at the end of a few seconds a stinging pain compelled me to 

 withdraw them. The soil, also, by reflecting the solar rays 

 from the sparkling fragments of mica and quartz, sometimes 

 becomes insupportably dazzling to the eye. 



Instead of the rolling waves and cool breezes of the sea, 

 this funereal region only gives out burning gusts, scorching 

 blasts which seem to issue from the gates of hell ; these 

 are the simoom, or poison-wind, as the word signifies in 

 Arabic. The camel driver knows this formidable enemy, 

 and so soon as he sees it looming in the horizon he raises 

 his hands to heaven and implores Allah ; the camels them- 

 selves seem terrified at its approach. A veil of reddish- 

 black invades the gleaming sky, and very soon a terrible 

 and burning wind rises, bearing clouds of fine, impalpable 

 sand, which severely irritates the eyes and makes its way 

 into the respiratory organs. 



The camels squat down and refuse to move, and the trav- 

 ellers have no chance of safety except by making a rampart 

 of the bodies of their beasts, and covering their heads so as 

 to protect themselves against this scourge. Entire caravans 

 have sometimes perished in these sand-storms ; it was one of 

 them that buried the army of Cambyses when it was trav- 

 ersing the desert. 



Maxime du Camp, in his charming work on the Nile, de- 

 scribes in the following terms one of these desert tempests, 

 to the least violent of which the name khamsin is given in 

 Egypt. " It comes towards one," he says, " growing, spread- 



