4:22 PLATEAU OF CAXAMARCA. 



from the autumnal tints which, in many of our forest trees, adorn 

 the woods of the temperate zone at the season of the fall of the leaf. 

 A single species of the South African family of Proteacese, Rhopala 

 ferruginea, descends here from the cold heights of the Paramo de 

 Yamoca to the hot plain of Chamaya. We often found here the 

 Porlieria hygrometrica (belonging to the Zygophyllese), which, by 

 the closing of the leaflets of its finely pinnated foliage, foretels an 

 impending change of weather, and especially the approach of rain, 

 much better than any of the Mimosacese. It very rarely deceived us. 

 We found at Chamaya rafts (balsas) in readiness to convey us to 

 Tomependa, which we desired to visit for the purpose of determining 

 the difference of longitude between Quito and the mouth of the 

 Chinchipe (a determination of some importance to the geography 

 of South America, on account of an old observation of* La Conda- 

 mine).( 10 ) We slept as usual under the open sky on the sandy 

 shore (Playa de Guayanchi) at the confluence of the Rio de Cham- 

 aya with the Amazons. The next day we embarked on the latter 

 river, and descended it to the Cataracts and Narrows (Pongo, in the 

 Quichua language, from puncu, door or gate) of Rentema, where 

 rocks of coarse-grained sandstone (conglomerate) rise like towers, 

 and form a rocky dam across the river. I measured a base line on 

 the flat and sandy shore, and found that at Tomependa the after- 

 wards mighty River of the Amazons is only a little above 1386 

 English feet across. In the celebrated River Narrow or Pongo of 

 Manseritche, between Santiago and San Borja, in a mountain ravine, 

 where at some points the overhanging rocks and the canopy of 

 foliage forbid more than a very feeble light to penetrate, and where 

 all the drift-wood, consisting of a countless number of trunks of 

 trees, is broken and dashed in pieces, the breadth of the stream is 

 under 160 English feet. The rocks by which all these Pongos or 

 Narrows are formed, undergo many changes in the course of centu- 

 ries. Thus a part of the rocks forming the Pongo de Rentema, 

 spoken of above, had been broken up by a high flood a year before 

 my journey; and there has ever been preserved among the inhabit- 

 ants, by tradition, a lively recollection of the precipitous fall of the 

 then towering masses of rock along the whole of the Pongo an 

 event which took place in the early part of the eighteenth century. 



