"The _balsa_ is a raft consisting of seven pieces or trunks of a peculiar and very light wood known as _palo de balsa_ (raft-wood); these pieces are either bound together or pinned with stakes of _chonta_, a kind of black palm which is very hard. The fore part of the raft is narrowed slightly, and the trunks are arranged on a curve whose elevation is perhaps eighteen inches, so that the sides are higher than the middle. Each of the seven trunks is perhaps five inches in diameter. On the framework thus made is placed a platform of plaited bamboos, known as _chairo_; this platform, which is intended for the reception of the cargo, and on which any passengers take their places, is called the _huaracha_. At each end of the raft a space of three to five feet is left free of any covering; here sit or stand the three boatmen who form the crew--two at the bow and one at the stern. A good raft is usually twenty-two to twenty-six feet long, by five to six feet wide, and will carry about 7-1/2 cwt. of cargo, as well as the three boatmen. "A _callapo_ or _monteria_ consists of two or three _balsas_ lashed together; such a raft will carry as much as 34 cwt. The crews of these rafts, according to their dimensions, consist of three to fifteen men; these men are Leco Indians, or Mosetenes, or Yuracares, who are highly skilled in this kind of navigation. "The pilot is the captain of the crew; he is naturally the calmest and the most expert; the _punteros_, who are stationed at the two ends, are the strongest; the rest are the rowers. The navigation of the _balsa_ is terribly hard work when mounting against a current; as a rule two men go ashore and tow the raft from the bank, pulling on a rope some fifteen yards in length; a third, armed with a pole sixteen or eighteen feet long, keeps the raft a certain distance from the bank, so that it shall not run aground. Where the water is too shallow to float the raft, it must be dragged over the stones in the bed of the river. In reaches where it is impossible to make one's way along the bank the raft is poled up-stream, a method of progression which costs more effort and is less speedy. "The crew of a _balsa_ or _monteria_ will usually navigate for some ten or twelve hours a day, during which they will perhaps make nine or ten miles; to rest, eat or sleep they go ashore, which action is known as _encostar_. "The navigation of the Mapiri (one of those rivers which run into the Beni) must be made in _balsas_ or _callapos_ manned by Leco Indians. From Mapiri the descent is rapid as far as Huanay, and the only obstacles are a few sunken reefs, which cause dangerous vortices in the impetuous stream. Where the Mapiri takes the name of Kaka (river of rocks)--that is, at the confluence of the Coroico--there are many dangerous passages full of surface rocks. This river finally flows into the Beni.