It is not only in the distribution of the vegetation that the agency of this predominant wind is apparent. The sand belts follow the same direction, so, too, do the clay ridges in Kharga and elsewhere; even the hills in the desert show in many cases a distinct tendency to have their longest diameter pointing up and down this north to south line. The predominant character of the northerly winds even has an effect upon the caravan roads; that, for instance, that runs from Farafra Oasis to Dakhla lies along a hollow among the sand dunes that occupy a large area in the centre of Farafra depression, that is kept permanently free of sand by the northerly wind that continually sweeps along it, so affording an easy path through what would otherwise be a most difficult dune-field to cross.
Once at ’Ain Amur I experienced a curious storm. It was a windy morning and I had been out after gazelle. On returning towards the camp, I saw in the distance what looked like very heavy rain falling in the ’Ain Amur Wady, so hurried back to the well to gain the shelter of the ruins in its neighbourhood.
The rain, however, turned out to be only a fog—or perhaps, since the well is 1,680 feet above sea-level, it would be more correct to say cloud—only a few drops fell; but for nearly an hour the whole district was enveloped in a thick white fog, while a furious wind sprung up and blew with great violence. At the end of that time the fog cleared off, the wind suddenly dropped and a sunny and unusually hot day followed. Fog, it is needless to say, is not a common occurrence in the desert.
The word oasis is unfortunately a very vague one, to which varying meanings are applied in different parts of the world. The dictionaries usually define it as a “fertile spot in a desert.” So far so good. The difficulty comes in when one attempts to apply this definition, for one is at once faced with two problems: what constitutes “fertility” and what is the size of a “spot”?
The Wad Ghirh district, for instance, in the south of Algeria, runs for some ninety-five miles from north to south, contains about forty villages, with their palm plantations, and a population of some fifteen thousand inhabitants. Each of these villages, with its palm plantations, is regarded as one oasis. The whole Wad Ghirh district being considered a group of oases.
Kharga and Dakhla Oases, which are separated from each other by about seventy-five miles of waterless desert, were considered by the ancient writers to form one oasis, known as the “great oasis.”
Kharga Oasis, according to Dr. John Ball, who surveyed it for the Egyptian Government, is about a hundred and forty miles long from north to south, contains some fifteen villages and has a population of seven thousand eight hundred odd. All this is considered even now to form one oasis.
To the north-west of Kharga lies a little place known as ’Ain Um Debadib, where there is a considerable area of scrub, with a few palms and sunt (i.e. acacia) trees. A certain amount of ground is cultivated here by a family from Kharga village, who, however, do not always reside there. This is usually considered a separate oasis.
In the eastern part of the Farafra depression is an area, some sixteen miles by twelve, covered with scrub, among which a few date palms, which seemed to be to some extent cultivated, are also to be seen. This place is known as Kairowin. There are no permanent houses or inhabitants, though frequently bedawin living in tents, or brushwood huts, are to be found there with their camels. The place contains several wells, and is sometimes described as an oasis, though the natives more usually allude to it as a hattia.
At ’Ain Amur, half-way between Kharga and Dakhla, is a well, some ruins, a patch of scrub and a palm or two. This, however, never has any residents—the well being only used by travellers between Kharga and Dakhla. This place is usually described as a hattia, though I have heard even this called an oasis.