Diary of navigation and reconnaissance of the Tebicuary River

The Diary of the navigation and reconnaissance of the Tebicuary River is one of several travel books that Azara wrote. His works dedicated to establishing, in a scientific way, the borders between the Spanish and Portuguese colonies. This activity also appears, among other texts of his, in his Official Correspondence.
Félix Azara studied the geography of South America and clarified in his maps the course of rivers and the place of mountains. Before him, those territories had been merely indicated, on inaccurate maps, by the expeditionaries of the early days of the Conquest of America.
In the Introduction of Pedro de Angelis, to the Journal of navigation and recognition of the Tebicuary River by Félix de Azara, the relevance of this book is commented in detail:

“Three centuries of negotiations and treaties were not enough to agree the Cortes of Madrid and Lisbon on the demarcation of their colonies, and these questions, which had begun with their domination in America, did not end with their decline. Each step they took, increased doubts and made their resolution more difficult; because they lacked an exact knowledge of the localities, nor could they acquire it for lack of documents.
After having conferred in Tordesillas, in Badajoz, in Lisbon, in Utrecht, without being able to reach a compromise, and leaving in all its obscurity the spirit of the concessions made by Alexander VI in his famous bull of 1593, the two powers returned to negotiate in Madrid and San Ildefonso, for the years 1750 and 1777. The cause that had paralyzed the first of these treaties, had disappeared with the expulsion of the Jesuits, and everything announced an easy and prompt execution of the second.
The Court of Madrid, which had always shown zeal and loyalty in the fulfillment of its promises, appointed commissioners so that, in agreement with the Portuguese, they would draw the new dividing line; and hastened to give all the instructions he thought necessary to fulfill the last stipulations.
These geodesic works, which embraced an immense space, from the immediate places to the Rio de la Plata to the mouths of the Amazons, surrounding in all its scope the interior border of Brazil, were entrusted to several commissions, which sought to form active and intelligent officers. One of them was the lord of Azara.”