The source of the great majority of the flowing wells of the oasis is the group of sandstones underlying the Impermeable Grey Shales. Although the beds of the series are nowhere visible to the eye, their general characters can be judged by an examination of the material brought to the surface during drilling operations. The samples prove that, in general lithological characters, the Artesian-water Sandstones do not essentially differ from those just described. Throughout the area over which boring operations have recently been carried out no well-defined, continuous, argillaceous bands have been met with, though lenticular intercalations of clayey strata are not uncommon. Up to the present time the base of the Artesian-water Sandstone has not been reached, although the deepest borings have been carried down to a depth of 122 metres below its junction with the confining shales above. The different bands vary considerably in coarseness and porosity, in hardness, and in the amount of cementing material between the individual grains of the rock, all of which characters have a marked influence on their capacity as water-carriers. Judging from their unfossiliferous nature, from the presence of thin seams of lignite associated with bands and nodules of iron pyrites, and from certain other considerations, we are led to infer that these sandstones were originally laid down on the bed of an immense inland fresh-water lake. During the past half-century the natives have put down a considerable number of deep bores in this and the neighbouring oasis. No written records concerning these are, however, available, so that in seeking information one has to rely on the memory of the men who sunk the wells. By careful cross-questioning I have collected a large amount of interesting and valuable information, but still, in describing the artesian wells themselves, it will be more satisfactory to confine our attention to those which have been drilled on the Headquarters area during the last two or three years, and of which accurate and reliable records have been preserved. The Headquarters area, occupying the central part of the depression between Kharga village and Jebel el Ghennîma, is one of the few large districts entirely devoid of old wells and traces of former cultivation. A combination of unfavourable circumstances appears to have led the ancient well-borers to avoid this district. Firstly, the general elevation is comparatively high, meaning small flows from wells of ordinary depth; secondly, the superficial alluvial deposit is clayey and heavy, necessitating a considerable expenditure of time and labour to bring it into satisfactory condition for cultivation; and, thirdly, and probably most important of all, the presence of a copious supply of sub-surface water, which would have greatly hampered, if not made impossible, the sinking of wells by the ancient system.