The Javary reference article from the English Wikipedia on 24-Apr-2004
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Javary

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The Javary, the boundary between Brazil and Peru, is another Amazon river tributary of importance. It is supposed to be navigable by canoe for 900 miles above its mouth to its sources among the Ucayali highlands, but only 260 have been found suitable for steam navigation. The Brazilian Boundary Commission ascended it in 1866 to the junction of the Shino with its Jaquirana branch. The country it traverses in its extremely sinuous course is very level, similar in character to that of the Jurua, and is a fostered wilderness occupied by a few savage hordes.