Geological Delineation of South America. 29 



I6OO square miles, which is bordered l)y the large rivers 

 Atabasso, Cassiguiare, Guiainia, and Orinoco, and repre- 

 sents a parallelogram, in which the water Hows on the four 

 opposite sides in opposite directions. In regard to the Ori- 

 noco, I found a fall of 1.51 tuises in the distance of 70 milci 

 from the mouth of Guaviarc to the Apure ; but from the 

 capital to the sea not more than eight toiscs. La Conda- 

 mine observed the same thing in regard to the river An)a- 

 zon, from the narrow pass of Paucis to Para, where it runs 

 through a district of 240 miles, but falls not more than 14 

 toiscs. It is not improbable that there might have been 

 on the north side of the cordillera of the coast of V^enezuthi 

 a plain as much lower than the plain of Orinoco as the plain 

 of Hio Negro is higher than that of Orinoco, and on this 

 account the former plain was covered by the water of the 

 cay. 



The t\\ o Llanos or plains which lie at the opposite ex- 

 remities of America exhibit a striking difference from that 

 v.hich lies between them, namely, tlie vale of tlie river 

 Amazon. The latter is covered by so impenetrable forests 

 that rivers alone can force a passage through them, and that 

 scarcely any other animals but such as frequent trees cv.:\ 

 live in that district; so much is vegetation favoured by the 

 continual rains under the equator. The case is quite dif- 

 ferent with the plains of Orinoco and Pampas j they are 

 level valleys covered with herbs, and savannahs which con- 

 tain only a few scattered palm-trees. The same heat, the 

 same want of water, and the same phesnomena of refrac- 

 tion, that is to say, the inverted image of objects seen float- 

 ing in the atmosphere, are observed here as in the deserts 

 of Africa and Arabia. But plains so perfect are nowhere 

 else to be found ; for the Mesa de Pavone and the Mesa de 

 Guanipa in 800 square miles contain no eminence of eight 

 pr ten inches in height. The plains of Lower Hungary, 

 on the west of Presburgh, have the greatest resenil)lance tu 

 them ; for the flat land of La Mancha, Champagne, Westpha- 

 lia, Brandenburgh, and Poland, is hilly when compared with 

 the Llanos of South America. Nothing but a long stagna- 

 tion of water could have produced so horizontal a bottom. 

 Traces of old cities are found here, but seldom are any seen 

 which rise like castles (La Piedra Guanan, longitude 69" 3' , 

 latitude I'' .59' Ab") in the Llano of Cassiguiare and of Uio 

 Negro. But from St. Borja to the mouth of the Black river 

 Condamine observed no eminence; and the Llano of Ori- 

 noco is also without islands. As the Morros of San .luan 

 belong to the southern declivity of the cordiif<jra of V'ene- 



zuola. 



