226 THE ATMOSPHEEE AND METEOEOLOGY. 



the air is agitated by tlie wind it then rises oscillating like the 

 smoke that rises from a high furnace, and the outlines of all ob- 

 jects seen through this vapour seem to tremble; if a calm reigns 

 in the atmosphere all the objects bathed by the denser strata are 

 reflected, as in a sheet of water, in the more expanded air, and 



.^M_Ji4_-ay^, 





Fig. 97.— Mirages at Yerdon, at the mouth of the Gironde. 



all their images appear double ; hence the name of espeio (mirror) 

 which the inhabitants of South America give to the mirage. In the 

 midst of the arid desert, at hundreds of miles from any stream, 

 bushes and rocks are reflected in the air as in the basin of a fountain ; 

 on the sea the ships, the shores, and signals are reproduced as on a 

 second ocean, even in the large squares of our cities which a burning 

 sun strikes, the statues sometimes seem to bathe their feet in a 

 crystalline water reflecting their graceful forms. This optical illusion 

 which thus paints imaginary objects even in our cities, is the *' Fata 

 Morgana " of Italy, the deceptive " Delibab " of the Magyar puszta, 

 and the " Thirst of the gazelle " on the plains of Hindostan. It 

 shows from afar fresh oases and rippling waters to the fatigued 

 travellers, who, where the deceitful picture glitters, only find aridity, 

 thirst, and perhaps death. In the deserts of Arabia the plain seems 

 every day transformed into an immense lake. In proportion as the 

 sun sinks the magic sheet retires, then it fades completely away, to 

 reappear the next day an hour or two before noon.* 



* Palgrave, A One Year's Travel in Central Arabia. 



