70 DR. B. SPRUCE OX EQUATORIAL-AMERICAN PALMS. 



Guayana as far as to the falls of the rivers that run direct to the 

 Atlantic, and westward nearly (or quite) to the foot of the Andes. 

 This may be described as one great sheet of granite and gneiss, 

 whose mean level is scarcely anywhere 500 feet above the sea, and 

 out of which rise peaks, masses, and ridges to a height of from a 

 few hundred to 10,000 feet, all of them destitute of running streams 

 and of human habitations ; but there is nowhere any continuous 

 range of mountains, or plateau, and (except towards its borders) 

 the granite has been entirely denuded of the stratified rocks that 

 once overlay it, and is now either naked or else overspread in 

 some places with a thin covering of white sand, and in others 

 (chiefly flats, hollows, and rifts) with a thick deposit of the fertile 

 "terra roxa," or red loam (decomposed gneiss, mica-schist, &c.), 

 which I have supposed to be lacustrine, but Professor Agassiz 

 says is glacial drift. 



3. The Diamond-Region — the elevated rocky region of Central 

 Brazil, where the largest southern affluents of the Amazon take 

 their rise, and where as we advance southward granite is the pre- 

 dominant rock. As I know nothing personally of either the 

 geology or the botany of this region, I shall not need to say more of 

 it at present. 



4. Tlie Amazon Region — middle and upper — comprising the 

 whole course of the main river and the country adjacent to its 

 banks, from the foot of the Andes down to the commencement of 

 the Para archipelago, or westward limit of the Coast-Eegion. As 

 far up the Amazon as to the mouth of the Coary, or perhaps a 

 little higher, there is stratified rock, either overlaid with alluvium 

 in the subriparial lands, or rising into flat-topped hills — relics of 

 a formation of horizontally stratified sandstones, 800 feet thick, 

 that once stretched continuously from the highlands of Brazil, 

 over the Amazon valley, the great granite flats of the Orinoco, 

 and the Llanos of the Apure, to the coast-range of Caracas, on 

 the borders of the Caribbean Sea ; but from the Coary to the foot 

 of the Andes the formation is (apparently) entirely alluvial. 



6. The Subandine Hegion, comprising the eastern slopes of the 

 Andes of Peru and Ecuador, up to 6000 feet, with a broad strip 

 of the great plain at their base. 



The geological formation of the oriental Peruvian Andes is 

 chiefly triassic, having the characteristic fossils, shales, and beds of 

 salt, of that region ; but the Equatorial Andes (or so much as I 



have seen of them, where the river Pastasa and its tributaries issue 



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