At the junction of 2 D the Cauches with that river, that Ecuadorean line descends the Chinchipe to the Maranon, and the Peruvian ascends to a point where it is intersected by a line following the eastern Cordillera northward to the head-waters of the Caqueta, or Japura, which forms the northern boundary down to the Brazilian frontier.
From the Japura southward to the Amazon, in 4° 13' 21" S., 69° 35' W., and thence up the Javary, or Yavari, to its source in 7° 8' 4" S., 73° 46' 30" W., as determined by a mixed commission, the line has been definitely settled.
The rivers forming this system are the Maranon from Puerto Limon to Tabatinga on the Brazilian frontier (484 m.), the Japura, Putumayo, Javary, Napo, Tigre, Huallaga, Ucayali, Pachitea, Jurua, Purus, Acre, Curaray and Aguarico all navigable over parts of their courses for steamers of 4 to 8 f t.
From the boundary line with Ecuador, on one of the inland trade routes with that republic, and on a principal line of communication with the great forested regions of the Caqueta (Japura), Putumayo and Napo.
The provisional line starts from the Japura river (known as the Caqueta in Colombia) in lat.
And average width of 320 m., may be inferred from the elevations of the Caqueta, or Japura river, which was explored by Crevaux in 1878-1879.