Distance from the Atlantic, 2514 miles; current in the Amazon, 3-1/4 miles per hour. The Pastaga has a rapid current and is full of obstructions to navigation; it is with much difficulty that canoes even can be forced up the river for any distance. On its head waters the Indians wash a considerable quantity of gold from the sand of the bed of the channel. BARRANCA. Latitude, 4 deg. 59' 53" south; longitude, 76 deg. 38' 38" west of Greenwich; magnetic variation, 7 deg. 46' 26" east; thermometer, 78 deg.; elevation above sea-level, 453 feet; distance from the Atlantic, 2545 miles; current, 3-1/4 miles per hour. Barranca is situated on a red clay bluff, about seventy feet high, on the north or left bank of the river, which is here narrow. Communication is kept up between Barranca and Moyabamba by way of the Aypena river to its head and thence by land. Barranca has been used as, but is not well adapted to be, a military post; gunboats could lay out of sight below, around a bend of the river, and shell it without being themselves exposed to its fire. MOUTH OF THE POTRO RIVER. Distance from the Atlantic, 2564 miles; current, 3-1/4 miles per hour. The Potro is navigable for small steamers a distance of sixty miles from its mouth, and is of importance as a link in the projected route from Chachapoyas to Limon on the Amazon. MOUTH OF THE MORONA RIVER. Distance from the Atlantic, 2576 miles; current, 3-1/2 miles per hour. Steamers ascend the Morona 300 miles, and at some stages of the water a greater distance. LIMON. Distance from the Atlantic, 2588 miles; current, 3-3/4 miles per hour. Limon is the terminus of a projected route from Chachapoyas to the Amazon; it is a place of no importance whatever in any other respect. PUNTA ACHUAL. Latitude, 4 deg. 15' 27" south; longitude 77 deg. 1' 28" west of Greenwich; magnetic variation, 8 deg. 18' 18" east; thermometer, 80 deg.; elevation above sea-level, 509 feet; distance from the Atlantic, 2612 miles; current, 3-3/4 miles per hour. Two miles above Punta Achual, at the Vuelta Calentura, or Calentura passage, the first serious difficulty is encountered in navigating the Upper Amazon; the difficulty there encountered is a strong current combined with a whirlpool in the channel of the river, but, with full heads of steam on, steamers are able to pass the vuelta and proceed on to Borja. At Vuelta Calentura the course of the river is from N.N.W. to S.S.E. BORJA.