EFFECTS OP THE MIEAOE. 103 



iurface of the ocean. The illusion was augmented when 

 the disk of the sun appearing on the horizon, repeated its 

 image by the effects of refraction, and, soon losing its 

 flattened form, ascended rapidly and straight towards the 

 zenith. 



Sunrise in the plains is the coolest moment of the day ; 

 but this change of temperature does not make a very lively 

 impression on the organs. We did not find the thermo- 

 meter in general sink below 27*5 ; while near Acapulco, at 

 Mexico, and in places equally low, the temperature at noon 

 is often 32, and at sunrise only 17 or 18. The level surface 

 of the ground in the Llanos, which, during the day, is never 

 in the shade, absorbs so much heat that, notwithstanding 

 the nocturnal radiation toward a sky without clouds, the 

 earth and air have not time to cool very sensibly from mid- 

 night to sunrise. 



In proportion as the sun rose towards the zenith, and the 

 earth and the strata of superincumbent air took different 

 temperatures, the phenomenon of the mirage displayed 

 itself in its numerous modifications. This phenomenon 

 is so common in every zone, that I mention it only 

 because we stopped to measure with some precision the 

 breadth of the aerial distance between the horizon and the 

 suspended object. There was a constant suspension, with- 

 out inversion. The little currents of air that swept the 

 surface of the soil had so variable a temperature that, in a 

 drove of wild oxen, one part appeared with the legs raised 

 above the surface of the ground, while the other rested on 

 it. The aerial distance was, according to the distance of 

 the animal, from 3' to 4'. Where tufts of the moriche palm 

 were found growing in long ranges, the extremities of these 

 green rows were suspended like the capes which were, for 

 so long a time, the subject of my observations at Cumana. 

 A well-informed person assured us, that he had seen, be- 

 tween Calabozo and Uritucu, the image of an animal in- 

 verted, without there being any direct image. Niebuhr 

 made a similar observation in Arabia. We several times 

 thought we saw on the horizon the figures of tumuli and 

 towers, which disappeared at intervals, without our being 

 ible to discern the real shape of the objects. They were 

 j-erhaps hillocks, or small eminences, situated beyond the 



