41 



latitude of 7°. As long as the Amazon flows 

 from south to north in the longitudinal valley? 

 between two chains of unequal height, (that is, 

 from the farms of Quivilla and Guancaybamba, 

 where the river is crossed on wooden bridges, as 

 far as the confluence of the Rio Chinch ipe,) 

 there are neither bars, nor any obstacle what- 

 ever to the navigation of boats. The falls of 

 water begin only where the Amazon turns 

 toward the east, crossing the intermedial chain 

 of the Andes, which widens considerably toward 

 the north. It meets with the first rocks of red 

 sand-stone, or of ancient conglomerate, between 

 Tambillo and the Pongo of Rentema, near 

 which I measured the breadth, depth, and swift- 

 ness of the waters ; and leaves the rocks of red 

 sand-stone east of the famous strait of Manse- 

 riche, near the Pongo of Tayuchuc, where the 

 hills rise no higher than 40 or 50 toises above 

 the level of the Amazon # . The river does not 



* The facts which I here relate respecting the Upper Ma- 

 ragnon, and the direction of the intermedial chain of the 

 Andes, which is connected with the principal chain by the 

 mountains of Zamora, and the Paramo of Assuay, differ from 

 what M. de la Condamine published in his works, and in 

 memoirs, in other respects very valuable. They are founded 

 on notions, which I had an opportunity of acquiring, during 

 my stay at Loxo, in the kingdom of Quito, at Tomependa, on 

 the borders of the Amazon, and in Peru, at Micuipampa, at 

 Caxamarca, and at Truxillo. It is sufficient to mention here, 

 that from Chili to the kingdom of New Granada, the Cor- 



