The native cultivators in certain parts of Kharga and Dakhla have for some years past found that their wells no longer discharge at so high a level as formerly, and in consequence some of their land has gone out of cultivation. From this fact, and from the evidence of the former greater prosperity of the oases which is afforded by the various ruins of temples, forts, and villages, by the large areas of formerly cultivated lands, and by numerous sanded-up wells, it has sometimes been inferred that the total yield of the oasis-wells is now but a fraction of what it formerly was. But, as Mr. Beadnell has pointed out,[24] the remains of the past which exist in the oases belong to successive generations, so that we cannot fairly draw such a conclusion from them; and the reduction or cessation of the discharge of certain wells does not necessarily imply any falling-off in the total water-output of the oases. Mr. Beadnell’s experiments on flowing wells in Kharga have clearly shown how the opening of a new well at a slightly lower level will affect the discharge of an old well, even one at a distance of a kilometre or more, by lowering the static head in its vicinity.[25] And since a large number of wells have been bored in recent years both in Kharga and Dakhla, it is most likely that the discharge from these wells has caused a falling-off in the yield of older ones situated at slightly higher levels. In this connection it will be well to note that it is not the mere _existence_ of a new well that affects the static head, but the _discharge_ from it. If the new well is securely closed so as to discharge nothing, it has then no effect on the static head and therefore none on the neighbouring wells. But for this to hold, it is important that the well which is closed should be closed throughout its entire depth; it is not sufficient merely to close its mouth so that it does not discharge any water on to the ground, for there may still be rapid leakage somewhere in the bore (unless effectively cased) into porous unsaturated underground strata. Owing to the rapid rate at which iron pipes are corroded in the wells of the oases, leakage of this kind is more likely to happen with an abandoned modern well cased with iron piping and plugged near the top, than with old wells which were filled up with clay and sand. These factors, the mutual interference of wells and the importance of preventing underground leakage, especially from abandoned wells, being now thoroughly understood, steps are being taken towards ensuring that future sites for new wells shall be judiciously selected, and that leakage and waste from abandoned wells shall be as far as possible arrested.