Geographically the Libyan Desert is the eastern and most inhospitable portion of the Sahara, or Great Desert of Africa. On the north and east its boundaries are clearly defined by the Mediterranean Sea and the Valley of the Nile; on the south it is bounded by the Darfur and Kordofan regions of the Egyptian Sudan; to the south-west its limits may be regarded as coterminous with the elevated districts of Tibesti; while on the west it stretches to the outlying oases of Fezzan and Tripoli. Its area is about 850,000 square miles, or approximately seven times that of the British Isles. With the exception of a narrow belt fringing the Mediterranean, the region is, to all intents and purposes, rainless, the occasional thunderstorms being extremely local, and seldom breaking over the same district in two consecutive years. In the more elevated deserts on the eastern side of the Nile rains appear to be of sufficiently frequent occurrence to maintain a water-supply in the isolated water-holes and valley-springs, and to allow of the growth of a fairly permanent though scanty herbage in the more favoured areas. The Eastern desert does, therefore, to some extent, support a migratory Arab population. On the other hand, the greater portion of the Libyan Desert is quite devoid of vegetation and water-holes, and is, in consequence, uninhabited even by nomad tribes. At the same time, the extreme barrenness of the region as a whole is in great measure counterbalanced by a number of isolated fertile oases, in which there is a permanent resident population, deriving its water-supplies entirely from underground sources. The term ‘oasis,’ an ancient Egyptian word signifying a resting-place, in its strict sense means a fertile spot in a desert, but in Egypt has usually been applied to a depression as a whole, each individual cultivated area being known by the name of the well from which its water is derived. The chief groups of oases in the Libyan Desert are the Siwan on the north, that of Kufra on the west, and the Egyptian, including the four large oases of Baharia, Farafra, Dakhla, and Kharga, on the east. The present volume deals more especially with the last of these.