OASIS ( in Greek, "Oasts, and sometimes A6ane) is the appellation given to those fertile spots watered by springs and covered with verdure which are scattered about the great sandy deserts of Africa. (Desaer.) In Arabic they are called wadys. The Arabic and the Greek name seem to contain the same root, and possibly the word may be originally a native African term. The most noted oases are in the Libyan desert, namely Anglia, Siwah, the greet oasis west of Thebes, or El Kliargele the little oasis, or With el Bahryeh, and several smaller ones which are noticed under EGYPT, in Geoo. Div. Fezran also may be considered as a great oasis of the Sahara. [FEZZAN; SAHARA, in GROH. Div.] The oases appear to be depressions in the table-land of Libya. On going from the Nile westward, the traveller gradually ascends till ha arrives at the summit of an elevated plain, which continues nearly level, or with slight undulations, for a considerable distance, and rises higher on advancing towards the south. Tho oases are valleys sunk in
this plain, and when you descend to one of them you find the level apace or plain of the oasis similar to a portion of the valley of Egypt, surrounded by steep hills of limestone at some distance from the culti vated land.. The low plain of the oasis is sandstone or clay, and from this last the water rises to the surface and fertilises the country ; and as the table-land is higher in the latitude of Thebes than in that of Lower Egypt, we may readily imagine that the water of the oases is conveyed from some elevated point to the south, and being retained by the bed of clay, rises to the surface wherever the limestone superstratum is removed.