Delimitation. – The great South American Confederation offers, with regard to its political position, conditions no less characteristic than those offered by its geographical position, since it is one of the terrestrial political units with a continuous surface which has the greatest number of neighbors, i.e. 7 states autonomous: 3 colonial possessions.
Limited to the north by Colombia, Venezuela, the three Guianas (British, Dutch, French) and the Atlantic (from Cape Orange, SE. Of Cayenne, up to Cape San Rocco), and towards the east exclusively from the Atlantic, great Confederation ends around noon with a very restricted area that has the character of a real tip, near the Uruguayan border. Along the western border, which presents an irregular trend, reflecting a whole series of territorial disputes regulated in recent times by peaceful agreements, Brazil borders with Uruguay, Argentina, Paraguay, Bolivia, Peru, with Colombia; therefore if possible agreements between Peru and Ecuador assign to this the disputed territory which now constitutes the extreme north-eastern area of Peru,
According to top-engineering-schools, the Brazilian-Uruguayan border, which stretches from the mouth of the Chuy in the Atlantic to the mouth of the Quarahim in Uruguay (left bank), was defined by the treaty of 1851 and by the conventions of the years 1852, 1853, 1909, 1917. The dividing line that runs, first of all, along the course of the Chuy, crosses, in the longitudinal direction, the Lagõa Mirim (small lagoon); then it follows the course of the Jaguarão Chico (Piccolo), the Mina, the São Luiz, and the Quarahim. The Brazilian-Argentine border, the general course of which was established with the conventions of 1857 and 1898 (after the arbitration ruling of the president of the United States of America, on the disputed territory between the Rio Uruguay and the Iguassu), and with the 1910 agreement, it follows the course of Uruguay from the mouth of the Quarahim to the mouth of the Rio Peperi-Guassú, then this river and the Rio S. Antonio, a tributary of the Iguassu. The demarcation on the ground leaves most of the grandiose cataracts of the Salto Grande do Iguassú in Argentine territory. The Brazilian-Paraguayan border, defined at the beginning of 1872, runs in the southern section along the Rio Paraná, then reaches, along the course of the Apá, the bank of Paraguay at Confluencia, and goes up the great river to the mouth of the Otuquis (Bahia Negra).
The Brazilian-Bolivian border was established with the treaties of 1867, 1903 (Petropolis treaty) and December 25, 1928. It runs along the Rio Paraguay in its southern section, which it leaves at 9 km. from Fort Coimbra, keeping at first in the general direction NO. and then in that N. through the lake area to which the mirror of Uberaba belongs, to then reach the sources of the Rio Verde, a tributary of the Guaporé, and then the Mamoré current and the Madeira current downstream of Villabella. From the mouth of the Abuná, a left tributary of Madeira, the dividing line runs along various river courses until reaching Tacna, on the right of the Acre (see).
The Brazilian-Peruvian border, generally defined since 1851 and definitively fixed after the 1909 convention – which closed long discussions about territorial disputes between Bolivia and Peru – runs from Tacna to Tabatinga on the high Amazons. It first follows the high course of the Acre then bends northwards to the mouth of the Santa Rosa nel Purús (left bank) and again to the South. up to the 10th southern parallel, to then reach the NW direction. the course of the Javary, which follows to its mouth at Tabatinga.
The border between Brazil and Ecuador, established by the treaty of 1904, with reservations for the requests of Peru, runs in the general direction NE., From Tabatinga to the mouth of the Apaporis in Japurá or Caquetá. This border has now also been accepted by Colombia, which following the Washington negotiations (1925) abandoned its claims on the triangular territory between the Amazon and Japurá, in exchange for the perpetual freedom of navigation on the rivers common to the two countries. granted by Brazil.
In the stretch between the left bank of the Japurá and the granite Pedra de Cucuhy – dominant from its 400 m. the alluvial plain between the Rio Negro and the Cassiquiare – the border was thus defined by the treaty of 1907: traced first of all along the Rio Apaporis, it cuts the Rio Tiguis, to then reach the high course of the Negro on the island of S. José opposite the Pedra de Cucuhy.
From this begins the Brazilian-Venetian border which, defined by the treaty of 1859 and by the protocols of 1905 and 1928, runs over the Tapirapeco, Parima and Pacaraima greenhouses and reaches Monte (or Cerro) Roraima. From here begins the border with British Guiana that the arbitration of Vittorio Emanuele III, king of Italy, of 6 June 1904, fixed from the sources of Tacatú (upper Rio Branco) to those of Corentyne along the watershed between the Amazons and Essequibo.
From the Corentyne to the Maroni spring basin, in the Serra di Tumuc-Humac (Tumucumaque), it is the border with Dutch Guiana (treaty of 1907). From the same Serra to the mouth of the Oyapock (at 4 ° 13 ′ 16 ″ lat. N.), where frontier features were recognized since the beginning of the century. XVIII, the border with French Guiana defined by the arbitration of the president of the Swiss Confederation in 1900 takes place.