y 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.

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 La