tream could be more convenient for
navigation, since the prevailing wind is south-east, and sailing boats
may make a continuous progress to the Peruvian frontier, dropping down
again with the current. In our own case the excellent engines of the
Esmeralda could disregard the sluggish flow of the stream, and we made
as rapid progress as if we were navigating a stagnant lake. For three
days we steamed north-westwards up a stream which even here, a thousand
miles from its mouth, was still so enormous that from its center the
two banks were mere shadows upon the distant skyline. On the fourth
day after leaving Manaos we turned into a tributary which at its mouth
was little smaller than the main stream. It narrowed rapidly, however,
and after two more days' steaming we reached an Indian village, where
the Professor insisted that we should land, and that the Esmeralda
should be sent back to Manaos. We should soon come upon rapids, he
explained, which would make its further use impossible. He added
privately that we were now approaching the door of the unknown country,
and that the fewer whom we took into our confidence the better it would
be. To this end also he made each of us give our word of honor that we
would publish or say nothing which would give any exact clue as to the
whereabouts of our travels, while the servants were all solemnly sworn
to the same effect. It is for this reason that I am compelled to be
vague in my narrative, and I would warn my readers that in any map or
diagram which I may give the relation of places to each other may be
correct, but the points of the compass are carefully confused, so that
in no way can it be taken as an actual guide to the country. Professor
Challenger's reasons for secrecy may be valid or not, but we had no
choice but to adopt them, for he was prepared to abandon the whole
expedition rather than modify the conditions upon which he would guide
us.

It was August 2nd when we snapped our last link with the outer world by
bidding farewell to the Esmeralda. Since then four days have passed,
during which we have engaged two large canoes from the Indians, made of
so light a material (skins over a bamboo framework) that we should be
able to carry them round any obstacle. These we have loaded with all
our effects, and have engaged two additional Indians to help us in the
navigation. I understand that they are the very two--Ataca and Ipetu
by name--who accompanied Professor