280 The Andes and the Amazon. 



CHAPTER XIX. 



The Valley of the Amazon. — Its Physical Geography. — Geology. — Cli- 

 mate. — Vegetation. 



From the Atlantic shore to the foot of the Andes, and 

 from the Orinoco to the Paraguay, stretches the great Val- 

 ley of the Amazon. In this vast area the United States 

 might be packed without touching its boundaries. It could 

 contain the basins of the Mississippi, the Danube, the Nile, 

 and the Hoang-Ho. It is girt on three sides by a wall of 

 mountains : on the north are the highlands of Guiana and 

 Venezuela ; on the west stand the Andes ; on the south 

 rise the table-lands of Matto Grosso. The valley begins at 

 such an altitude, that on the western edge vegetation dif- 

 fers as much from the vegetation at Para, though in the 

 same latitude, as the flora of Canada from the flora of the 

 West Indies. 



The greater part of the region drained by the Amazon, 

 however, is not a valley proper, but an extensive plain. 

 From the mouth of the Napo to the ocean, a distance of 

 eighteen hundred miles in a straight line, the slope is one 

 foot in five miles.* At Coca, on the Napo, the altitude is 

 850 feet, according to our observations ; at Tinga Maria, 

 on the Huallaga, it is 2200 according to Herndon ; at the 

 junction of the Negro with the Cassiquiari, it is 400 ac- 

 cording to Wallace; at the mouth of the Mamore, it is 800 

 according to Gibbon ; at the Pongo de Manseriche, below 



* Professor Agassiz gives the average slope as hardly more than a foot 

 in ten miles, which is based on the farther assertion that the distance from 

 Tabatinga to the sea-shore is more than 2000 miles in a straight line. The 

 distance is not 1600, or exactly 1500, from Para. — See ^4 Journey in Bra- 

 zil, p. 349. 



