751 



the point of the island of Roudah. An eminent 

 scientific gentleman, who has recently resided 

 on the banks of the Oroonoko, Mr. Zea, will 

 supply what is wanting in my observations on a 

 point so important. The people believe, that 

 every twenty-five years the Oroonoko rises 

 three feet higher than common ; but the idea of 

 this cycle does not rest on any precise measures. 

 We know by the testimony of antiquity, that 

 the oscillations of the Nile have been sensibly 

 the same with respect to their height and dura- 

 tion for thousands of years : which is a proof 

 well worthy of attention, that the mean state of 

 the humidity and the temperature does not vary 

 in that vast basin. Will this constancy in phy_ 

 sical phenomena, this equilibrium of the ele- 

 ments, be preserved in the New World also after 

 some ages of cultivation ? I think we may re- 

 ply in the affirmative ; for the united efforts of 

 man cannot have an influence on the general 

 causes, on which the climate of Guyana de- 

 pends. 



According to the barometric height of San 

 Fernando de Apure, I find from that town to the 

 Boca de Navios the slope of the Apure and the 

 Lower Oroonoko to be three inches and a quar- 

 ter to a nautical mile of nine hundred and fifty 

 toises*. We may be surprised at the strength 



* The Apure itself has a slope of thirteen inches to the 

 mile. See vol. iv, p. 455. 



