385 



nounced the line of demarcation, and promised to recognize 

 no other limits between Brazil, Buenos Ayres, and Peru, 

 than the ridge of some mountains, and the course of the 

 rivers. This convention declared formally " that it was im- 

 possible to fix by observations of longitude the line of de- 

 marcation on the coast, and in the interior}" a confession 

 the more singular, as Don Jorge Juan, and Don Antonio de 

 Ulloa, had proved, in a learned memoir (Dissertation historka 

 y geogrqfica sobre el meridiano de demarcation entre los domi- 

 nio8 de Portugal y de Espatia), published after their return 

 from Quito, in 1749, that the limit ought to be fixed by the 

 tenor of the treaty of Tordesillas, and according to two 

 modes of interpretation of which that treaty is susceptible, 

 either 1° 50', or 3° 14 on the east of the town of Grand 

 Para. The convention of 1750 was renewed and confirmed 

 at Madrid, October 11th, 1777 ; but the execution of stipu- 

 lations made without local knowledge, and in consulting only 

 very imperfect maps, was attended with greater difficulties. 

 Nothing more was attempted on the side of the Oroonoko, 

 and the Rio Negro ; the whole attention of the two courts 

 was directed towards the limits of Paraguay, and the banks 

 of the Caqueta, the Rio Blanco, and the Amazon. The Bri- 

 gadier Don Jose Varela, was sent (1782 — 1789) to Monte- 

 video, M. d'Azara to Paraguay, and M. Requena to Maynas. 

 However incomplete the labours of the commissaries have 

 remained, it cannot be doubted that astronomical geography 

 will derive great advantages, if not the results only of their 

 investigation are made public, but the observations on which 

 those results are founded. The map by Azara of Paraguay, 

 and those of Brazil, executed at Rio Janeiro, by order of the 

 minister of marine, Don Rodrigo de Souza Coutinho, in 

 1804, by the captain of a frigate, Don Antonio Peres da 

 Silva Pontes Lemos, have been rectified according to a part 

 of those observations j but the longitudes being all chrono- 

 metrical, the discordance in the time pieces of the Spanish 

 VOL. VI. 2 c 



