398 



wherever it was exposed to the Sun, at 52*5° *. 

 The instrument, raised eighteen inches above 

 the sand, marked 42*8°; and at six feet high, 

 38*7°. The temperature of the air under the 

 shade of a ceiba, was 36*2°. These observations 

 were made during a dead calm. As soon as the 

 wind began to blow, the temperature of the air 

 rose 3° ; yet we were not enveloped by a wind 

 of sand: but the strata of air had been in con- 

 tact with a soil more strongly heated, or through 

 which whirlwinds of sand had passed. This 

 western part of the Llanos is the hottest, be- 

 cause it receives air that has already crossed 

 the rest of the barren steppe. The same differ- 

 ence has been observed between the eastern 

 and western parts of the deserts of Africa, where 

 the tradewinds blow. 



The heat augments sensibly in the Llanos 

 during the time of rains, particularly in the 

 month of July, when the sky is cloudy, and 

 sends back the radiant heat toward the earth. 

 During this season the breeze entirely ceases ; 

 and, according to good therm ometrical observa- 

 tions made by Mr. Pozo, the thermometer rises 

 in the shade to 39° and 39*5°^, though kept 

 at the distance of more than fifteen feet from 

 the ground. As we approached the banks of 



* 42° R. 

 + 31-2° or 31'6° R. 



