Neither in Ain Jaja nor Ain Dakhakhin is there any trace of wooden casing similar to that with which the ancient wells of Northern Kharga are so commonly lined. This bears out the conclusion to which I was led on other grounds—that the original outlets were many metres lower than at present, on the level of the surrounding plain, in fact. The eminences of Jaja and Dakhakhin appear to have been formed almost entirely by the gradual accumulation of blown sand and clay-dust, compacted and held together by vegetation. The material is swept by the prevalent winds from the clay plains and sandy deserts lying to the north, and deposited on the cultivated lands, owing to the presence thereon of water and vegetation. Its deposition is encouraged by the peasants, as the admixture of sand and clay forms a loam of suitable texture for agricultural purposes, and is regarded as having considerable fertilizing value. [Illustration: AIN DAKHAKHIN.] There is little doubt that originally nearly all the wells in Southern Kharga had their outlets on the same level as the plain. Owing to the periodical deposition of wind-borne materials, the cultivated lands have gradually risen, until at the present day they form, in the majority of cases, terraces standing well above the general level. This continual raising of the land has necessitated a corresponding elevation of the wells, with the result that the wooden linings originally put into the bores have been completely lost sight of. Instead of issuing from a clean, unobstructed hole, the water has now to force its way upwards through a great mass of sandy mud, and before it can be utilized it has to rise to a much higher level than formerly. Little wonder, then, that the flows of the majority of these wells have very much decreased, with the consequence that the cultivated tracts are much smaller than of old. In more than one case the outlet of a well had, in modern times, risen to such a height that the discharge had become reduced to a mere trickle. Twenty or twenty-five years ago, for instance, Ain Dakhakhin was on the summit of an eminence which, by the slow accumulation of sand and clay, had reached a height of 30 metres above the surrounding plain. Remedial measures were then taken by the inhabitants, and its level reduced by between 8 and 9 metres, the present level of the well and highest fields being 23 metres above the plain. The height of a cultivated terrace above the general level of the plain on which the well was originally sunk affords some measure of its antiquity. It is difficult, however, in the absence of observations extending over a number of years, to estimate what the general rate of accumulation may have been. It would, moreover, vary greatly with local conditions, but if an average rate of a centimetre a year be assumed, the age of Ain Dakhakhin is indicated as being something over 3,000 years.