These short tunnels, tapping the water of artesian wells bored on high ground, are quite insignificant compared with the extensive systems of subterranean aqueducts driven into the solid rock in various localities in the north of the oasis. The most remarkable of these are found at Um el Dabâdib, at Qasr Lebekha, and in the neighbourhood of Qasr Gyb. They were made with the object of obtaining auxiliary supplies of water from the Surface-water Sandstone, and were especially applicable to localities where this sandstone has an extensive development and forms hills or plateaux above the general level of the floor of the oasis. Although it is difficult to believe that the supplies of water obtained were commensurate with the time and labour involved in the construction of the collecting tunnels, we may safely assume that the engineers who so carefully planned and carried out the works had fully considered the results to be looked for. The ruins of villages and the traces of formerly cultivated tracts show that sufficient water was obtained to enable fairly large colonies to exist, though after the withdrawal of the Romans these outlying districts were abandoned, the aqueducts silted up, and the cultivated lands reverted to the desert. The ruins of Um el Dabâdib are situated under the northern wall of the depression, and distant about 36 kilometres N.N.W. of Kharga village, the route usually followed lying between the hill-massifs of Jebel Têr and Jebel Tarif. A better route is afforded by the caravan road running from Meheriq to Ain Amûr, Um el Dabâdib lying somewhat to the north of the track at a distance of 25 kilometres from the village. Dr. J. Ball, in the course of his survey of the oasis, visited Um el Dabâdib in 1898, and thought it possible that one of the tunnels, which he observed ran northwards from the neighbourhood of the ruins, had originally formed a means of communication with some unknown and formerly inhabited depression to the north of the escarpment. Its real nature was, however, well known to the Kharga people, and a year or two later Sheikh Hassan Hanadi, a brother of the present Omda of Kharga village, got together a number of men and cleaned out one of the tunnels from top to bottom, with the result that, after a lapse of perhaps 1,000 years, water again flowed from the mouth of the aqueduct, and enabled a small agricultural colony to establish itself on the ruined site of the original founders.