VALLEY OF THE AMAZONS. 
201 
Its extent is stupendous; it stretches from 
the Atlantic shore, through the whole width 
of Brazil, into Peru, to the very foot of the 
Andes. Humboldt speaks of it “ in the vast 
i 
plains of the Amazons, in the eastern boun¬ 
dary of Jaen de Bracamoros,” and says,“ This 
prodigious extension of red sandstone in the 
low grounds stretching along the east of the 
Andes is one of the most striking phenomena 
I observed during my examination of rocks 
in the equinoctial regions.” * When the great 
natural philosopher wrote these lines, he had 
no idea how much these deposits extended 
beyond the field of his observations. Indeed, 
they are not limited to the main bed of the 
Amazons; they have been followed along the 
* Bohn’s edition of Humboldt’s Personal Narrative, p. 134. 
Humboldt alludes to these formations repeatedly : it is true 
that he refers them to the ancient conglomerates of the 
Devonian age, but his description agrees so perfectly with 
what I have observed along the banks of the Amazons, that 
there can be no doubt he speaks of the same tiling. He 
wrote at a time when many of the results of modern geology 
were unknown, and his explanation of the phenomena was 
then perfectly natural. The passage from which the few 
lines in the text are taken shows that these deposits extend 
even to the Llanos. 
