In the Times of Scrambles in the Land of the Amazons - The Scramble for the Amazon and the Lost Paradise of Euclides da Cunha - page 78

Map 3. Idelfonso line.
The Treaty of San Idelfonso (1777)
The territorial lines indicated by Treaty of Madrid and the Treaty of Idelfonso were
meant to be demarcated by joint boundary commissions. This task was somewhat com-
pleted in the La Plata areas, but the circumstances of the northern boundaries—hostile
Indians,theproblemsofsurveyinginthedenseforestsandimpassable swamplands, and
general recalcitrance on both sides—meant that the western Amazonian holdings were