immense cost and difficulty of transporting materials through such a country. A few adventurers, however, still continue to wash for gold in the Challuma or Taccuma. In the part of its course above the _lavaderos_ this river descends rapidly from an isolated range of forest-covered precipitous hills, and in one place its waters plunge down in a cascade, with a sheer fall of forty feet.[306] The gold-seekers of the Challuma have penetrated further into the forests, and nearer to the main stream of the Purus, than any other explorers; and their discovery of the Challuma, and of the auriferous hills near its banks, has added something to our geographical knowledge of this region. The remaining villages on the eastern slopes of the Caravayan Andes are Patambuco, Sandia, Cuyo-cuyo, Quiaca, Sina, and the farm of Saqui, on the frontier of Bolivia. The river of Sandia has one of its sources near the pass twenty miles north-east of Crucero, whence it flows past Sandia, and for many leagues down a narrow gorge, with magnificent mountains rising up abruptly on either side. At a distance of twenty miles below Sandia, in a part of the ravine called Ypara, the coca and coffee plantations commence, at a height of 5000 feet above the sea. Beyond Ypara cultivation ceases, and the river, now increased to double its former size by its junction with the Huari-huari, flows for many leagues between mountains covered from their summits with a dense tropical forest. This region is known as San Juan del Oro, once famous for its gold-washings; and here the royal town of the same name stood, founded by the fugitive Almagristas, and afterwards tenanted by the Señores Mulattos, but long since destroyed and abandoned. The forests contain chinchona-trees of valuable species, and, until the last fourteen years, they were frequented by bark-collectors. While flowing through the forests of San Juan del Oro the river takes a turn to the westward, and, at a distance of sixty miles from Sandia, enters the Hatun-yunca, or Valle Grande, where the people of Sandia have very extensive coca and coffee plantations. The curve here made by the river is so considerable that the people from Sandia reach their farms in the Valle Grande by leaving the ravine above Ypara, and making their way across the grass-covered mountains. The coffee-plants in these farms receive no attention whatever from the time they are planted, so that, instead of the dense well-pruned bushes of India or Ceylon, they grow into tall straggling trees about twelve feet high, with a very small harvest of berries on each, but each berry well exposed to the sun. The coffee is certainly excellent. Passing through the Valle Grande the river flows on past Versailles, where it receives the golden Challuma, and, uniting with all the other rivers of Caravaya, becomes that great Ynambari which finally effects a junction with the Madre de Dios, and forms the main stream of the mighty Purus.