Kio Napo. 199 



is a full Spanish mile. Below Coca the river throws 

 out numerous canals, which, isolating portions of the for- 

 est-clad lowlands, create numerous picturesque islands. 

 Around and between them the river winds, usually mak- 

 ing one bend in every league. The tall trees covering 

 them are bound together by creeping plants into a thick 

 jungle, the home of capybaras and the lair of the jaguar. 

 The islands, entirely alluvial, are periodically flooded, and 

 undergo a constant round of decay and renovation. In- 

 deed, the whole river annually changes its channel, so that 

 navigation is somewliat difficult. The Indians, on coming 

 to a fork, were frequently at a loss to know which was the 

 main channel. Then, too, the river is full of snags and 

 plaias, or low, shelving sand-banks, rising just above the 

 water-level — the resort of turtles during the eg^ season. It 

 was interesting to trace the bed of the river as we floated 

 down ; on the rapid slope of the Cordilleras rushing over 

 or rolling along huge boulders, which farther on were rap- 

 idly reduced in size, till, in time, boulders were broken into 

 pebbles, pebbles turned into sand, and sand reduced to im- 

 palpable mud.* The plaias are not auriferous. Below 

 Coca there is a wilderness of lagunes, all connected with 

 the river, the undisturbed retreat of innumerable water- 

 fowl. The only spot on the Napo where the underlying 

 rocks are exposed is near Napo village. There it is a dark 

 slate, gently dipping east. Farther west, in fact, through- 

 out this side of the Andes, the prevailing rock is mica- 

 schist. But the entire Napo country is covered with an 

 alluvial bed, on the average ten feet thick. 



* From specimens of sand which we obtained at different points in descend- 

 ing the river, we find that at Coca it contains 17.5 per cent, of pm-e quartz 

 grains, the rest being colored dark with augite ; at the mouth of the Napo 

 there is 50 per cent, of pure quartz, the other half being light-colored and 

 feldspathic. 



