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los to Angostura, the capital of Guyana, than 

 that of ascending the Rio Negro as far as the 

 mission of Maroa ; the rest of the navigation 

 would be performed by means of the currents of 

 the Temi, the Atabapo, and the Oroonoko* 



The road from San Carlos to San Fernando 

 de Atabapo is far more disagreeable, and half 

 as long again by the Cassiquiare, as by Javita 

 and the Canno Pimichin. In this region, into 

 which the expedition of the boundaries carried 

 no astronomical instruments, I determined, by 

 means of the chronometer of Louis Berthoud, 

 and by the meridional heights of stars, the situ- 

 ations of San Balthasar de Atabapo, Javita, San 

 Carlos del Rio Negro, the rock Culimacavi, and 

 of Esmeralda; the map I have constructed 

 has consequently solved the doubts that remain- 

 ed of the respective distances of the Christian 

 establishments. When no other road exists but 

 that of tortuous and intermingled rivers, when 

 little villages are hidden amid thick forests, and 

 when, in a country entirely flat, no mountain, 

 no eminent object is visible from two points at 

 once, it is only in the sky that we can read 

 where we are upon the Earth. In the wildest 

 countries of the torrid zone we feel more than 

 any where the want of astronomical observa- 

 tions. They are not only useful means of finish- 

 ing and improving maps, but are indispensable 

 for tracing the first sketch of the ground. 



