THESOURCEOFTHENILE. 6y s
floods; and therefore, on the firft confideration, this annual and equal increafe mull be impoflible.
At Bafboch, before the Nile enters Sennaar, I made feve- ral hundred trials upon its fediment, as it then came down, from the cultivated country of Abyflinia ; I thereby found this fediment furpriiingly fmall, being a mixture of fat earth, and a fmall quantity of fand. At the junction of the Nile and Aftaboras I did the fame, taking up the water from the middle of the ftream, and, having evaporated it afterwards, I found little more fediment than at Sennaar; the water was indeed whiter, and the greateft part of the fediment was fand. I repeated this experiment at Syene with the utmoft attention, where the Nile leaves Nubia, and enters Egypt, and I found the quantity of fediment fully nine times increafed from what it was at Sennaar, and in it only a trifle of black earth, all the rett being fand. The experiment at Rofetto was not fo often repeated as the others ; but the refult was, that, in the ftrength of the in- undation, the fediment confided moftly of fand, and, to- wards the end, was much the greater part of earth. I think thefe experiments conclufive, as neither the Nile coming frefh from Abyffinia, nor the Atbara, though joined by the Mareb, likewife from the fame country, brought any great quantity of foil from thence.
It was at Syene that the water fhould have been moil charged with mud, for all the acceflion it was to bring to Egypt was then in its itream ; but there the chief part of the fediment was fand, fanned and ventilated with perpetual hot winds, and fpread on the furface of the burning defert, never refrefhed with the dew of heaven. In that dreary
4 Qji defert,
