Between 33 and 18 degrees south latitude, between the parallels of Valparaiso and Arica, the Andes present towards the east three remarkable spurs, the Sierra de Cordova, the Sierra de Salta, and the Nevados de Cochabamba. Travellers partly cross and partly go along the side of the Sierra de Cordova (between 33 and 31 degrees of latitude) in their way from Buenos Ayres to Mendoza; it may be said to be the most southern promontory which advances, in the Pampas, towards the meridian of 65 degrees; it gives birth to the great river known by the name of Desaguadero de Mendoza and extends from San Juan de la Frontera and San Juan de la Punta to the town of Cordova. The second spur, called the Sierra de Salta and the Jujui, of which the greatest breadth is 25 degrees of latitude, widens from the valley of Catamarca and San Miguel del Tucuman, in the direction of the Rio Vermejo (longitude 64 degrees). Finally, the third and most majestic spur, the Sierra Nevada de Cochabamba and Santa Cruz (from 22 to 17 1/2 degrees of latitude), is linked with the knot of the mountains of Porco. It forms the points of partition (divortia aquarum, between the basin of the Amazon and that of the Rio de la Plata. The Cachimayo and the Pilcomayo, which rise between Potosi, Talavera de la Puna, and La Plata or Chuquisaca, run in the direction of south-east, while the Parapiti and the Guapey (Guapaiz, or Rio de Mizque) pour their waters into the Mamori, to north-east. The ridge of partition being near Chayanta, south of Mizque, Tomina and Pomabamba, nearly on the southern declivity of the Sierra de Cochabamba in latitude 19 and 20 degrees, the Rio Guapey flows round the whole group, before it reaches the plains of the Amazon, as in Europe the Poprad, a tributary of the Vistula, makes a circuit in its course from the southern part of the Carpathians to the plains of Poland. I have already observed above, that where the mountains cease (west* of the meridian of 66 1/2 degrees (* I agree with Captain Basil Hall, in fixing the port of Valparaiso in 71 degrees 31 minutes west of Greenwich, and I place Cordova 8 degrees 40 minutes, and Santa Cruz de la Sierra 7 degrees 4 minutes east of Valparaiso. The longitudes mentioned in the text refer always to the meridian of the Observatory of Paris.)) the partition ridge of Cochabamba goes up towards the north-east, to 16 degrees of latitude, forming, by the intersection of two slightly inclined planes, only one ridge amidst the savannahs, and separating the waters of the Guapore, a tributary of the Madeira, from those of the Aguapehy and Jauru, tributaries of the Rio Paraguay. This vast country between Santa Cruz de la Sierra, Villabella, and Matogrosso, is one of the least known parts of South America. The two spurs of Cordova and Salta present only a mountainous territory of small elevation, and linked to the foot of the Andes of Chile. Cochabamba, on the contrary, attains