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 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.
It is worthy of note that the principal rivers of these three classes - the Patia, Cauca, Magdalena, Caqueta and Putumayo - all have their sources on the high plateaus of southern Colombia and within a comparatively limited area.
The principal rivers of the Amazon system are the Napo, the upper part of which forms the provisional boundary line with Ecuador, the Putumayo or Ica, and the Caqueta or Japura (Yapura), which flow from the Andes entirely across the eastern plains, and the Guainia, which rises on the northern slopes of the Serra Tunaji near the provisional Brazilian frontier, and flows with a great northward curve to the Venezuelan and Brazilian frontiers, and is thereafter known as the Rio Negro, one of the largest tributaries of the Amazon.
According to Uricoechea there are at least twenty-seven native languages spoken in the western part of Colombia, fourteen in Tolima, thirteen in the region of the Caqueta, twelve in Panama, Bolivar and Magdalena, ten in Bogota and Cundinamarca, and thirty-four in the region of the Meta, while twelve had died out during the preceding century.
The four intendencias are called Goajira, Meta, Alto Caqueta and Putumayo, and their aggregate area is estimated to be considerably more than half of the republic. The first covers the Goajira peninsula, which formerly belonged to the department of Magdalena, and the other three roughly correspond to the drainage basins of the three great rivers of the eastern plains whose names they bear.