er of
real importance. It was not a minor affluent of some other affluent.
But we were still wholly in the dark as to where it came out. It was
still possible, although exceedingly improbable, that it entered the
Gy-Parana, as another river of substantially the same size, near its
mouth. It was much more likely, but not probable, that it entered the
Tapajos. It was probable, although far from certain, that it entered
the Madeira low down, near its point of junction with the Amazon. In
this event it was likely, although again far from certain, that its
mouth would prove to be the Aripuanan. The Aripuanan does not appear
on the maps as a river of any size; on a good standard map of South
America which I had with me its name does not appear at all, although
a dotted indication of a small river or creek at about the right place
probably represents it. Nevertheless, from the report of one of his
lieutenants who had examined its mouth, and from the stories of the
rubber-gatherers, or seringueiros, Colonel Rondon had come to the
conclusion that this was the largest affluent of the Madeira, with
such a body of water that it must have a big drainage basin. He
thought that the Duvida was probably one of its head streams--although
every existing map represented the lay of the land to be such as to
render impossible the existence of such a river system and drainage
basin. The rubber-gatherers reported that they had gone many days'
journey up the river, to a point where there was a series of heavy
rapids with above them the junction point of two large rivers, one
entering from the west. Beyond this they had difficulties because of
the hostility of the Indians; and where the junction point was no one
could say. On the chance Colonel Rondon had directed one of his
subordinate officers, Lieutenant Pyrineus, to try to meet us, with
boats and provisions, by ascending the Aripuanan to the point of entry
of its first big affluent. This was the course followed when Amilcar
had been directed to try to meet the explorers who in 1909 came down
the Gy-Parana. At that time the effort was a failure, and the two
parties never met; but we might have better luck, and in any event the
chance was worth taking.

On the morning following our camping by the mouth of the Rio Kermit,
Colonel Rondon took a good deal of pains in getting a big post set up
at the entry of the smaller river into the Duvida. Then he summoned
me, and all the others, to attend th