r a number of
hours, or sometimes for a day or two, at Bahia, Maceio, Pernambuco,
Parahiba, Natal, Ceara, and Maranham, I had many opportunities for
observation. It was my friend Major Coutinho, already an experienced
Amazonian traveller, who first told me that this formation continued
through the whole valley of the Amazons, and was also to be found on all
of its affluents which he had visited, although he had never thought of
referring it to so recent a period. And here let me interrupt the course
of my remarks to say, that the facts recorded in this article are by no
means exclusively the result of my own investigations. They are in great
part due to this able and intelligent young Brazilian, a member of the
government corps of engineers, who, by the kindness of the Emperor, was
associated with me in my Amazonian expedition. I can truly say that he
has been my good genius throughout the whole journey, saving me, by his
previous knowledge of the ground, from the futile and misdirected
expenditure of means and time often inevitable in a new country, where
one is imperfectly acquainted both with the people and their language.
We have worked together in this investigation; my only advantage over
him being my greater familiarity with like phenomena in Europe and North
America, and consequent readiness in the practical handling of the
facts, and in perceiving their connection. Major Coutinho's assertion,
that on the banks of the Amazons I should find the same red,
unstratified clay as in Rio and along the southern coast, seemed to me
at first almost incredible, impressed as I was with the generally
received notions as to the ancient character of the Amazonian deposits,
referred by Humboldt to the Devonian, and by Martins to the Triassic
period, and considered by all travellers to be at least as old as the
Tertiaries. The result, however, confirmed his report, at least so far
as the component materials of the formation are concerned; but, as will
be seen hereafter, the mode of their deposition, and the time at which
it took place, have not been the same at the north and south; and this
difference of circumstances has modified the aspect of a formation
essentially the same throughout. At first sight, it would indeed appear
that this formation, as it exists in the valley of the Amazons, is
identical with that of Rio; but it differs from it in the rarity of its
boulders, and in showing occasional signs of stratification. It is a