PLATEAU OF CAXAMABCA. 401 



specimen in Commerson's Herbarium. But on a nearer ap- 

 proach we found that these trees were really without leaves, 

 properly so called, and that what, from a distant view, we 

 had mistaken for leaves, were bright rose-coloured bracts. 

 Owing to the purity and freshness of the colour, the effect was 

 totally different from that of the hue which so pleasingly clothes 

 many of our forest- trees in autumn. The Rhopala ferruginea, 

 a species of the South African family of the Proteaceae, has 

 found its way hither, having descended from the cool heights 

 of the Paramo de Yamoca into the warm plains of the Cha- 

 maya. "We likewise frequently saw here the beautifully pin- 

 nated Porlieria hygrometrica, one of the ZygophylleaB, which, 

 by the closing of its leaves, indicates change of weather, gene- 

 rally the approach of rain. This plant is more certain in its 

 tokens than any of the Mimosaceae, and it very rarely deceived 

 us. 



At Chamaya we found rafts (balsas) in readiness to convey us 

 to Tomependa, where we wished to determine the difference of 

 longitude between Quito and the mouth of the Chinchipe ; a 

 point of some importance to the geography of South America 

 on account of an old observation of La Condamine (10). We 

 slept as usual in the open air, and our resting-place was on 

 the sandy shore called the Playa de Guayanchi, at the conflu- 

 ence of the Rio de Chamaya and the Amazon. Next morning 

 we proceeded down the latter river as far as the Cataract 

 and the Narrows, or the Pongo of Rentema. Pongo, the 

 name given to River Narrows by the natives, is a cor- 

 ruption of the word Puncu, which, in the Quichua language, 

 signifies a door or gate. In the Pongo de Rentema huge 

 masses of rock consisting of coarse-grained sandstone (conglo- 

 merate), rise up like towers and form a rocky dam across the 

 stream. I measured a base line on the flat sandy shore, 

 and found that the Amazon River, which, further east- 

 wards, spreads into such mighty width, is, at Tomependa, 

 scarcely 1400 feet broad. In the celebrated River Narrows, 



2 D 



