The depression known as the Wadi Rayan, discovered by Mr. Cope Whitehouse about 1883, situated some 40 kilometres west of the Nile Valley and about 100 kilometres south of the latitude of Cairo, has been so frequently described and considered in regard to its utilization as a reservoir or as a flood-protection for Lower Egypt, that I need say little about it beyond a reference to the principal published works dealing with it.[12] There is no other depression in the Libyan Desert which has received so much attention from the economic standpoint. That the Wadi Rayan has not already been utilized as a reservoir has depended on a variety of considerations, of which one of the principal has been the doubts always entertained as to whether there might not be an underground leakage from it, resulting not only in a loss of part of the stored water, but also in damage to the adjacent flourishing province of the Faiyum. These doubts will not be lessened by the converging lines of evidence which I shall bring forward in dealing with the artesian water- supplies, all leading to the conclusion that there is an underground water-connection between the various depressions of the Egyptian Libyan Desert. Of late years, however, it has been proposed to make use of the Wadi Rayan, not as a reservoir, but as a sump for disposing of the drainage water of Upper Egypt by evaporation; and to this, in consequence of the lower level at which the water would stand in the depression, there is far less objection from the point of view of possible leakage or damage to the Faiyum.