North of the _nudo_ or knot in the Loja province, spurs and ravines lead off from the high mountain range. Here swift flowing streams descend in a region called wild and savage. Those rising farthest north reach the Amazon at a more eastern point than the streams rising nearer, at the south; so the mention of the principal rivers of the eastern slope will begin with the most southern and western tributary. It may be remembered that the Amazon is formed by the union of the Marañón and the Ucayali Rivers, both flowing northwest in Peru, the former, the one nearer the Pacific coast. Above 6° S. Lat. the Marañón turns sharply east, flowing with northerly and southerly deviations, receiving in its course many tributaries before and after breaking through the East Cordillera of Peru at the Pongo de Manseriche. Here the waters of the previously broad river pass through an extraordinary chasm 3 miles long and 100 feet wide. The walls are not 2000 feet high as often stated; in one or two places they may rise 40 feet perpendicularly, but usually they are wooded slopes, rising in a single locality perhaps 2000 feet.[6] The principal rivers flowing from Ecuador into the Marañón or Amazon are the Chinchipe, Santiago, Morona, Pastaza, Tigre, Nanay, and Napo. These with the streams from Colombia drain the northwest part of the Amazon Basin and are capable of adding much to the economic value of the region. The few white settlements existing are as nothing in this vast wilderness. [6] See Geographical Journal, October, 1920 =The Chinchipe River= rises in southern Loja and after receiving many tributaries flows into the Marañón a little below where that river runs northeast. The lower part of the Chinchipe is navigable. =The Santiago River= rises near the town of Loja between the two Cordilleras. Several of its important tributaries rise in Loja, or in the Cuenca basin farther north. One of these, the Pauta, has a branch rising only 30 miles from the Gulf of Guayaquil, a source nearer the Pacific than that of any other river flowing into the Atlantic unless it be in the very south of Chile. The Santiago enters the Marañón a little above the rapids of the Pongo Manseriche. At the mouth of the stream was once a town, Santiago, which like Borja below the Pongo was destroyed by savages.