SIX MONTHS IK MEXICO. 



75 



further, when we found good bread and 

 pulque, or fermented juice of the aloe. This 

 drink is not pleasant to those unaccustomed 

 to it, as the smell is disagreeable ; but it is 

 generally considered to be very wholesome, 

 and accordingly there is a great consumption 

 of it. 



Our route proceeded through desolate and 

 parched plains, and we were often deluded by 

 what appeared to be water; the deception being 

 so great, that images of the objects around, 

 were reflected in a very extraordinary man- 

 ner.* We observed in this day^s journey, 



* This remarkable optical deception occurs under par- 

 ticular states of the atmosphere, on the verge of the horizon, 

 and particularly in warm climates, on extensive plains, &c. 

 Objects often appear with extraordinary elevation, double, 

 or inverted. This singular phenomenon is obviously caused 

 by refraction of the rays of light passing through the at- 

 mosphere, the lower strata of which have different densities. 

 When this effect is confined to the elevation of an object, 

 our seamen call it looming. This play of vision has received 

 the appellation of Mirage from the French, and by the 

 Italians it is called Fata Morgana : for further information 



