=The Morona River.= Two of the many tributaries of the Morona rise in the East Cordillera at heights above 13,000 and 14,000 feet north of the Apuay knot. At high water the Morona is navigable for 300 miles, at low water for 200, for steamers drawing from 2 to 4 feet, and also two of its tributaries; but due to the tortuous course of the river the 300 miles equals but 120 in a straight line. Earlier many flourishing missions existed in this section, but in the last century the Huambisa Indians inhabiting the upper reaches of the Santiago and the Morona almost exterminated the Indians who had been civilized. So recently as February, 1913, members of the same tribe massacred the soldiers of a Peruvian outpost. This, notwithstanding, was later re-established by Peru. =The Pastaza River=, rising in the basin of Riobamba at a height of nearly 15,000 feet, flows through a little known district receiving many tributaries. The lower part is navigable for steamers at high water to the Huasaga branch, 120 miles, and 200 miles farther by canoe. This fluvial system drains the basins of Latacunga, Ambato, and Riobamba, the snows of Chimborazo, Cotopaxi, and other peaks contributing to its waters. A spot where the unified river at an altitude of about 6000 feet in one leap makes a splendid fall of 190 feet is said to be one of the most picturesque scenes in the Andes. =The River Tigre= belongs to the region of the plains, though some of its affluents rise in the East Cordillera. Although in volume not to be compared to the Pastaza or the Napo it is quite as important, being navigable for steamers of 4 to 8 feet draught at high water for over 400 miles, and in low water for steamers drawing 2 to 4 feet; 100 miles more on the Corriente branch and 40 on the Pucasuro, with an additional 1260 miles by canoe on its various tributaries. The region traversed is rich in natural products and with over 100 tributaries the river deserves remembrance. It enters the Marañón 40 miles above the Ucayali. =The Nanay=, a much smaller plains river with a slow current, yet with a high bank and a healthful climate, may be ascended for 105 miles and has some importance.