The river Huari-huari, which is formed by two streams flowing from the villages of Sina and Quiaca, joins the river of Sandia about thirty miles below that town, and their united streams compose the Ynambari. Finally the river Tambopata rises near a farm called Saqui, just within the boundary between Peru and Bolivia, at the foot of a ridge of the Eastern Cordillera. After a course of forty miles it receives the river of San Blas, on the banks of which the people of the Sina village have their coca-plantations. Eighty miles lower down the Tambopata unites with the river Pablo-bamba, on its right bank, at a place called Putina-puncu. The Pablo-bamba rises in a hill called Corpa-ychu on the very frontier of Bolivia, and is only divided from the Tambopata, during its whole course, by a single range of hills. The frontier between the two republics has never been surveyed. Below Putina-puncu the united waters of the two rivers enter the vast forest-covered plains into which the spurs of the Andes finally subside, and henceforth its course is entirely unknown. I think it probable, however, that the Tambopata finds its way direct to the Purus, without previously uniting with the Ynambari. The respective distances and populations of the villages of Caravaya are as follows:-- Miles. Population. Ollachea to Ituata 12} " Corani 10} " Ayapata 18} " Ccoasa 10} 12,000 " Usicayus 18} " Phara 20} " Limbani 8} " Patambuco 16 1,000 " Sandia 12 4,000 " Cuyo-cuyo 15 2,000 " Quiaca 21 600 " Sina 20 600 " Bolivian frontier 12 --- ------ 192 20,200 --- Macusani to Crucero 30 1,800 ------ Population of Caravaya 22,000 ------