Note A — PHYSICAL HISTORY OF THE VALLEY OF THE AMAZONS.

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 thing. 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.