To the royal jurisdictions of Buenos-Ayres and Rio de la Plata, of Tucuman and Asumpcion, must be added a region named Chaco. Its length is 300 leagues, its breadth 100. Tucuman, the region De las Charcas, Santa Cruz de la Sierra, and the rivers De la Plata and Paraguay surround Chaco; on both sides it is bounded by the mountains which stretch from Cordoba to the Peruvian silver mines at the cities of Lipes and Potosi, thence to Santa Cruz de la Sierra, and lastly to the lake Mamore, where they terminate. This territory, throughout its whole extent, enjoys a salubrious climate, and a rich fertile soil. Here it gently swells into pleasant hillocks, there sinks into fertile vallies, affording rich pasturage to horses and cattle of all kinds. It is adorned with woods, and a variety of excellent trees. On the Peruvian side, stones and rocks that seem to threaten the skies, cover immense tracts of land. Towards the south, it is utterly destitute of stones, pebbles, or sand, though you dig to the depth of fourteen feet. Incredible multitudes of strange beasts, birds, amphibious animals, and fishes present themselves to the eye. Besides lakes and rivulets, the ground is watered by noble rivers, which overflow the banks and inundate the sloping plains to a great extent. The most considerable stream in Chaco is the Rio Grande, or Vermejo, which has its source in the Peruvian mountains, and is increased by the accession of many rivers, till it shortly becomes navigable for small ships. It flows down in a very deep channel, with the most rapid course; washes the cities of Guadalcazar and Concepcion, long since devastated by the savages, and at about thirty leagues distance from thence, mingles its waters with the Paraguay, a little before its junction with the Parana. The waters of the Rio Grande, which abound in fish, are pronounced by authors to be salubrious, especially to those who labour under a difficulty of urine, or any disease of the bladder. The second place to this river is occupied by the Pilcomayo, which also flows from the Peruvian mountains. The distance between it and the Rio Grande is reckoned at thirty leagues. It is not navigable at all times, nor in all places. Nearly eighty leagues from its junction with the Paraguay, it splits into two arms, forming an island of as many leagues in length. The first of these arms which flows into the Paraguay, within sight of Asumpcion, is called by the Guaranies _Araguaaỹ_, or the wise river; possibly because the greatest sagacity is requisite to effect its navigation. The whole island is annually flooded, so that both branches of the river coalescing into one channel, it must be attributed to fortune, rather than to skill, if any pilot pass over the opposing shallows, and the meanders of its waters in safety. The other arm, which retains the name of _Pilcomayo_, unites with the Paraguay at about the distance of nine leagues to the south of Asumpcion.