Marianas are also found on the upper reaches of the Putumayo across to the Yapura.
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 principal tribes are the Quijos or Canelos, who are settled about the headwaters of the Napo, on the eastern slopes of the Andes, and are in great part grouped about the missions; the Jivaros who inhabit the valley of the Pastaza; the Zaparos who occupy the forest region between the Pastaza and Napo; the Piojes of the middle Napo, and eastward to the Putumayo; and the Iquitos and Mazanes of the lower Napo and Tigre, chiefly in territory occupied by Peru.
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 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.
The ISA or Putumayo, west of and parallel to the Yapurï¿½was found more agreeable to navigate by Crevaux.