In the following list I have summarized all the water sources known to me in order of latitude from north to south. I believe the list contains all sources that are of importance, but it is doubtless far from being complete as regards the rock basins of the mountain areas for two reasons. Firstly, the Arabs are often reluctant to point out the sources, more especially in the more arid parts of the Ababda country; and secondly, as already remarked, since the rock basins depend for their supplies entirely on comparatively recent rainfall around them, they vary very much in yield in different years, so that basins which are of great use in one year may be totally dry the next, and _vice-versa_, and guides seldom take the trouble to point out a dry basin, even if in some other year it may have held a useful store of water. With regard to the accuracy of the positions given in the list, it may be remarked that in the case of wells actually visited the position is given to seconds, and the localisation may be relied on within at most a few hundred metres; while for wells not actually seen but whose positions were pointed out by guides from some distance, the coordinates are usually only given to minutes, and these positions are uncertain by larger amounts, up to two or three kilometres in extreme cases. It must not be assumed that water supplies can _always_ be obtained at all the localities named. As already remarked, rock basins will usually only be full if rain has fallen in the district comparatively recently, large rock basins may furnish supplies for a year after rainfall, but the smaller ones last only a few months, weeks, or even days. The reserves are the wells, most of which never run dry except after a succession of rainless years. But when rock basins are full, many of the wells are filled with downwash, and digging must be resorted to in order to re-open them. A traveller arriving at a “well” sometimes finds no evidence whatever of its existence beyond the guides pointing to a spot on the ground with the statement “_el bir hena_” (the well is here). The explanation is that the well has been filled with alluvial matter washed down the valley by recent rain; but that same rainfall will have filled the rock basins in the hills, and the Arabs leave the digging out of the well until the basins are empty again. In other cases a well may be found to be dry through the water-level having sunk below the depth to which the well was last opened, and by deepening it a foot or so one may obtain a supply. The notes in the column headed “Remarks,” on the quality of the water of the various sources, are mostly based on the observations of a single year, and must therefore only be taken as general guides. Usually, the shorter the interval since rain has fallen, the better are the supplies, both in quantity and quality. LIST OF WATER SOURCES.[121]