750 



respect to space, or to the magnitude of the 

 oscillations, than with regard to time, or the 

 period of the maxima and minima. Having been 

 able to measure but imperfectly the risings of the 

 river, I report, not without hesitation, estimates, 

 that differ much from each other*. Foreign 

 pilots admit ninety feet for the ordinary rise in 

 the Lower Oroonoko. Mr. de Pons, who has in 

 general collected very accurate notions during 

 his stay at Caraceas, fixes it at thirteen fathoms. 

 The heights naturally vary according to the 

 breadth of the bed, and the number of tributary 

 streams which the principal trunk receives. The 

 swellings of the Nile in Upper Egypt are from 

 thirty to thirty-five feet ; at Cairo twenty-three 

 feet; and in the northern part of the Delta 

 four feet. It appears, that the mean rise at 

 Angostura does not exceed twenty-four or twen- 

 ty-five feet. In this spot an island, situate in 

 the middle of the river, would furnish the same 

 facility for measuring the increase, as that 

 afforded by the nilorneter (Megyas) placed at 



* Tuckey, Maritime Geogr., vol. iv, p. 309. Hippisley, 

 Exped. to the Oroonoko, p. 38. Gumilla, vol. i, p. 56 — 59. 

 Depons, vol. iii, p. 301. The greatest height of the rise of 

 the Missisippi is, at Natchez, fifty-five English feet. This 

 river (the largest perhaps of the whole temperate zone) is at 

 it's maximum from February to May j at it's minimum in Au- 

 gust and September, Ellicot, Journal of an Expedition to the 

 Ohio, p. 120. 



