152 STEPPES AND DESERTS. 



lides); or provided with leaves (Pereskise). Many extend high up 

 the sides of the mountains. Near the foot of the Chimborazo, in 

 the elevated sandy plain around Riobamba, I have found a new kind 

 of Pitahaya, the Cactus sepiuin, even at a height of 10,000 (10,660 

 Eng.) feet. (Humboldt, Bonpland, and Kunth, Synopsis Planta- 

 rum fequinoct. Orbis novi, t. iii. p. 370.) 



( M ) p. 37. " The scene in the Steppe is suddenly changed." 

 I have- endeavored to depict the coming in of the rainy season, 

 and the signs by which it is announced. The usual deep dark 

 azure of the sky in the tropics arises from the more complete solu- 

 tion of the vapor contained in the atmosphere. The cyanometer 

 indicates a paler blue as soon as' the vapors begin to be precipitated. 

 The dark spot or patch in the constellation of the Southern Cross 

 gradually becomes indistinct as the transparency of the atmosphere 

 diminishes, and this alteration announces the near approach of rain. 

 The brightness of -the Magellanic clouds (Nubecula major and 

 minor), gradually vanishes in - a similar manner. The fixed stars, 

 which before shone like planets with a steady, tranquil, and not 

 trembling light, now scintillate even in the zenith, where the vapors 

 are least. (See Arago, in my Relation hist. t. i. p. 623.) All 

 these appearances are the results of the increased quantity of vapor 

 diffused in the atmosphere. 



( 39 ) p. 38. " Awakened from a torpid state ty the first fall of rain " 

 Extreme dryness produces in plants and animals the same phe- 

 nomena as does the withdrawal of the stimulus of heat. Many 

 tropical trees and plants shed their leaves during the dry season. 

 The crocodiles and other amphibious animals hide themselves in the 

 mud, where they lie apparently dead, like animals in a state of 

 hybernation or plunged into winter sleep by cold. (See my Rela- 

 tion historique, t. ii. pp. 192 and 626.) 



f 40 ) p. 38. ." The aspect of a vast inland sea." 

 Nowhere are "these inundations more extensive than in the net- 

 work of rivers formed by the Apure, the Arachuna, Pajara, Arauca, 



