Geological Delineation of Smith America, 27 



bed in this place. This cordillera has two remarkable 

 properties. In the first place, as has been remarked in 

 other ridges, the southern declivity is much steeper than 

 the northern: the high summits of Caravami, Jao, of the 

 volcano of Duida, Maraguaea, &c., all lie towards the 

 south, and are there cut into perpendicular precipices. In 

 the second place, this cordillera does not seem to contain a 

 single rock of alluvial mountains, and consequently has bor- 

 rowed nothing from the organized kingdom. On our pas- 

 sage over this ridge wc observed nothing but granite, gnieis, 

 micaceous schist, and hornblend schist ; nowhere a covering 

 of sand-stone or alluvial chalk, ^^ hich on the cordillera of 

 Venezuela on the coast rises to the height of <J7<J toises 

 above the level of the sea. Had the proximity of the equator 

 and the rotation of the earth any influence on this phoenu-» 

 men on ? 



The third ch^in of original mountaiiis, the cordillera of 

 Chiquitos, is known only from the accounts of some per- 

 sons who have resided at Buenos-Ayres and travelled 

 through the Pampas. ' It vmitcs the Andes of Peru and 

 Chili with the ridges of Brasil and Paraguay as it stretches 

 from La Paz, Potosi, and Tucuman, through the provinces 

 of Maxos, Chiquitos, and Chaco, towards the government 

 of the Mines and of St. P^ul in Brasil, Their highest sum- 

 mits seem to be situated between the latitude of 1 5° and 20** 

 south, as the streams between the rivers Amazon and La 

 Plata divide theniselves at that height. 



Between the three cordillcras, the direction of which we 

 have hitherto followed, lie three broad and deep valleys. 

 1st, The valley between the south side of the cordillera oi' 

 Venezuela, on the coast, and the cordillera of the Cataracts, 

 or the vailey of Orinoco and Apure, between latitude 8** 

 and 10°. 2d, The valley of the rivers Negro and Amazon, 

 bordered by the Parima ridge and the cordillera of Chiqui- 

 tos, between latitude 3° north and 10° south, 3d, The val- 

 ley of Pampas of Buenos -Ayres, which extends from Saint 

 Cruz of Sierra to Cape Virgin, between 19" and 32° south 

 latitude. The first and second valley are in some measure 

 united by the destruction of a part of the I'arima cordillera. 

 I do not know whether this be the case also with the Pampas 

 and valley of the Amazon ; it, however, appears that it is 

 not, though the Llanos of Monso form a sort of cana.1 which 

 descends from north-west to south-east. All these immense 

 valleys or plains are entirely open towards the east, as they 

 run out into a low sandv coast : towards the west they arc 

 shut by tliC chain pf the high Andes. There jire tome creeks 



{ansa) 



