743 



Sierra Nevada de Merida, and traverses the pro- 

 vince of Varinas, 



The cause of the periodical swellings of the 

 Oroonoko acts equally on all the rivers, that 

 take rise in the torrid zone. After the vernal 

 equinox, the cessation of the breezes announces 

 the season of rains. The increase of the rivers, 

 which may be considered as natural ombrometer's, 

 is in proportion to the quantity of water, that 

 falls in the different regions. This quantity, in 

 the centre of the forests of the Upper Oroonoko 

 and the Rio Negro, appeared to me to exceed 

 90 or 1 00 inches annually # . Such of the na- 

 tives therefore, as have lived beneath the misty 

 sky of the Esmeralda and the Atabapo, know, 

 without the smallest notion of natural philoso- 

 phy, what Eudoxus and Eratosthenes knew here- 

 tofore that the inundations of the great rivers 

 are owing solely to the equatorial rains. The 

 following is the usual progress of the oscillations 

 of the Oroonoko. Immediately after the vernal 

 equinox (the people say on the 25th of March), 

 the commencement of the rising is perceived. 

 It is at first only an inch in twenty-four hours ; 



summit that enters into the region of perpetual snows, but 

 that Sierra Nevada de Merida (lat. 7° 50'), and the Nevada de 

 Chita (lat. 5° 45'). 



* See above, p. 248 and 32G. 



+ Strabo, Lib. 17, p. 7U9. Diod. Sic, Lib. 1, c. 5. 



