637 



to the ancient communications that are sup- 

 posed to have existed between that part of the 

 world and the north of Mexico. 



We went down the Oroonoko in two days, 

 from Carichana to the mission of Uruana, after 

 having again passed the celebrated strait of 

 Baraguan*. We stopped several times to de- 

 termine the velocity of the river, and it's tem- 

 perature at the surface, which was 27*4°. 

 The velocity was found to be two feet in a 

 second (sixty- two toises in 3' 6"), in places 

 where the bed of the Oroonoko was more than 

 twelve thousand feet broad, and from ten to 

 twelve fathoms deep. The slope of the river 

 is in fact extremely gentle from the great Cata- 

 racts to Angostura-}-; and, if a barometric mea- 

 surement were wanting, the difference of height 

 might be determined by approximation., by mea- 

 suring from time to time the velocity of the 

 stream, and the extent of the section in breadth 

 and depth;};. We had some observations of the 



* See vol iv, chap. 19, p. 502. 



+ The descent of the Nile also, from Cairo to Rosetta, a 

 distance of fifty-nine leagues (at 2273 t.), is only four inches 

 in a league. Descr. de V Egypte Moderne, vol. i, p. 58. 



+ Edinburgh Review, vol. xxiv, p. 414. According to 

 Clark and Lewis, the velocity of the Missouri, near where it 

 flows into the Mississipi, is seven feet in a second, and in 

 some places more than twelve feet ; which equals the velo- 

 city of the Cassiquiare. See above, p. 418. 



