[Transcriber's note: This article has been extracted and prepared from _The Geographical Journal_, v. 70, 1927.] PROBLEMS OF THE LIBYAN DESERT John Ball, O.B.E., D.Sc., M.Inst.C.E., F.G.S., Director of Desert Surveys, Egypt _Map following p._ 96. THERE can be few tracts of the Earth’s surface which present such a number and variety of interesting geographical problems as the Libyan Desert. The following are some of the more puzzling of the questions which have been asked at various times since I made my first acquaintance with the desert thirty years ago: 1. Did the Nile, or a branch of it, ever flow through the Libyan Desert to the west of the present Nile Valley? 2. By what natural agency were the great depressions in the Libyan Desert excavated? 3. Can other depressions in this region, besides the much-discussed Wadi Rayan, be considered possible of utilization in connection with irrigation, flood-protection, or drainage of the Nile Delta, or as sources of water-power for Egypt? 4. Whence comes the artesian water of the oases? 5. Why have not certain lakes, such as Sittra and Bahrein, situated as they are in an almost rainless region, long since dried up? 6. Can the present scanty supplies of drinkable water derived from local rainfall along the Egyptian Mediterranean Littoral be supplemented by artesian borings? 7. Are the artesian water-supplies of the oases gradually diminishing? 8. Where shall we look for the mysterious “Zerzura,” or “Oasis of the Blacks”? Are there any other “lost” oases remaining to be discovered? 9. Can the present difficulties of travel in the Libyan Desert, which are chiefly due to scarcity of water, be alleviated by the sinking of new wells? 10. Where are the “Tortoise Marshes” of Ptolemy? 11. What determined the peculiar distribution of the sand-dunes, some of which extend in straight lines for hundreds of kilometres? 12. What is the full extent of the distribution of flint implements and pottery, of which accumulations have been found in what are now among the most desolate parts of the desert, and what light does this throw on human history and climatic changes? To most of these questions no completely satisfactory answers have as yet been given, though several of them have been the subject of painstaking investigations by many workers. Our knowledge of the facts bearing on them has, however, increased considerably during the past few years; and in the present paper I propose briefly to review the various questions in the light of the latest available data concerning them.