Latitude, 4 deg. 31' 37" south; longitude, 77 deg. 29' 43" west of Greenwich; thermometer, 76 deg.; elevation above sea-level, 516 feet; distance from the Atlantic, 2660 miles; current, 3-3/4 miles per hour. At Borja the navigation of the Upper Amazon ends; the river in its whole course from Laracocha to Borja, a distance of 500 miles, is a mountain torrent, impracticable for navigation even by canoes. The length of the Amazon, from its source at Laracocha to the Atlantic ocean, is 3160 miles, but the distance from the Atlantic to the source of the Ucayali is still greater. It usually takes a steamer 69 steaming hours to ascend the river from Iquitos to Borja, and 35 steaming hours to descend from Borja to Iquitos. DISTANCES. In the following list of distances between places on the Amazon, from its mouth to its source in Lake Laracocha, the distances for the Lower Amazon are taken from the best Brazilian authorities that could be consulted; the distances for the Upper Amazon, from the Brazilian frontier to the head of steamer navigation at Borja, were measured by the Peruvian Hydrographical Commission of the Amazon; and the distance from Borja, the head of navigation, to the source of the river in Lake Laracocha, is given as estimated by the best Peruvian authorities. LIST OF DISTANCES ON THE AMAZON. Lower Amazon. Miles. Atlantic ocean to Para 75 Para to Breves 146 Breves to Garupa 123 Garupa to Porto de Moz 48 Porto de Moz to Prainha 96 Prainha to Monte Alegre 44 Monte Alegre to Santarem 60 Santarem to Obidos 68 Obidos to Villa Bella 95 Villa Bella to Serpa 137 Serpa to Manaos 110 From the Atlantic to Manaos, 1002 miles. Manaos to Cudajos 155 Cudajos to Coary 84 Coary to Tefe (Ega) 107 Tefe (Ega) to Fonte Boa 133 Fonte Boa to Tonantius 140 Tonantius to San Paulo 95 San Paulo, mouth of the Yavari river 90 The mouth of the Yavari marks the boundary line between Peru and Brazil on the south side of the Amazon. Mouth of the Yavari to Tabatinga 14 Brazilian frontier port on the north side of the Amazon. From the Atlantic to Tabatinga, 1825 miles.