The average height of the centre of the depression in the neighbourhood of the village of Kharga is approximately the same as that of the Nile Valley plain in the latitude of Farshut.
Ball, by comparison of a series of aneroid barometer readings with the barometric records for the same period at the Cairo observatory, deduced the value of a point near Kharga village as 86 metres above sea-level, and used this as his datum in calculating the levels of other parts of the oasis. Previous aneroid determinations of the same point had been made by Cailliaud (104 and 118 metres) and by Jordan (68 metres). But even when the greatest possible precautions are exercised, aneroid determinations, especially when made with a single instrument, are necessarily unreliable, and still more so when used for calculating the levels of different points on a plain having only comparatively slight irregularities of surface.
Utilizing the figure obtained by the railway surveyors for a point near the termination of the line, we get values of 58 and 60 metres above sea-level for Kharga village and Bore No. 1 at headquarters respectively, and a bench-mark at the latter place, having a value of 60·1, is used as the datum from which all the heights given in this book are calculated. Unfortunately it is not possible, owing to the lack of sufficient check-levels, to state the limit of probable error, and it must therefore be understood that the value of our datum, which in the meantime may be accepted as the best obtainable, is subject to future revision.
From this central point (Bore No. 1) lines of levels have recently been carried in every direction by Mr. F. E. Apted and myself, with the result that it has been shown that the general level of the floor of the oasis rises steadily to the north and falls to the south. These levels have in all cases been checked, and may, using the datum mentioned, be accepted as fairly reliable, the closing errors on the different loops being generally within a very few centimetres. The altitudes of a few reference points in each district are given here.
| District. | Point. | Altitude. |
|---|---|---|
| Headquarters | Bore No. 1 | 60·1 |
| ” | Bore No. 44 | 53·1 |
| Kharga | Bir Ain el Gôs | 70·2 |
| ” | Ain el Sabbagh | 56·9 |
| ” | Ain Zaaf | 87·7 |
| ” | Temple of Hibis (floor) | 75·0 |
| Meheriq | Bir Qattara | 56·6 |
| ” | Ain Mahmud | 64·8 |
| ” | Ain el Burg | 69·6 |
| ” | Ain el Qasr | 76·0 |
| ” | Ain el Ghazâl | 84·6 |
| South of headquarters | Ain Harrân | 43·5 |
| ” ” ” | Ain Ali Morad | 33·0 |
| ” ” ” | Ain Bellal | 28·4 |
| ” ” ” | Ain el Tawîl | 19·7 |
| Gennâh | Ain Estakherab | 71·3 |
| ” | Ain Magarin | 74·6 |
| ” | Ain el Ghuâta (north) | 48·2 |
| ” | Ain Zaiyan | 41·6 |
| ” | Qasr Zaiyan | 20·7 |
| El Dêr | Bore No. 22 | 92·3 |
The Government Survey maps show a portion of the oasis floor as lying below sea-level, the difference of height between the Kharga village datum and a point just south of Qasr Zaiyan being given as 104 metres. Detailed surveying shows that this estimate is excessive, the true difference being about 37 metres only. Although no actual reading has yet been obtained below sea-level—the lowest being +2·6 metres at a point 3½ kilometres north-east of the northern end of the Gorn el Gennâh, or nearly midway between that hill and Ain el Tawîl—it is evident that in this district the floor is only very slightly higher than the sea, and it may be that at one or two points its level is actually lower.
South of Qasr Zaiyan no revision of previous levels has as yet been made. According to Ball’s figures, the village of Beris is approximately 10 metres lower than Kharga.
While discussing the subject of levels it may be useful to note the relative heights of the escarpments and hills within the oasis. The edge of the eastern plateau varies from 350 to 400 metres above sea-level, while the plateau to the north of Um el Dabâdib has a general level of about 400 metres. Jebel Tarif appears to be very slightly higher, while the highest peak on Jebel Têr is not much more than 300 metres. The altitudes of these points with reference to the village were mostly determined by Ball by trigonometric observations with an eight-inch theodolite, and can therefore be relied on as being accurate.
CHAPTER V
THE NORTHERN VILLAGES
Population — Relation of Population to Water-Supply — Trade in Dates — Imports — Taxation on Date-Palms and Wells — Measurement of Wells — Revenue derived from the Oasis — Origin of Inhabitants — Kharga Village — Industries — Ancient and Modern Wells — Meheriq Village — Troubles with Sand — Migration of Villagers — Ain el Tawîl and other Hamlets — Gennâh Village — Famous Wells — Ain Estakherab — Ochreous Waters of certain Wells — Ain el Ghuâta — Bulaq Village — Doum-Palms — Tomb of Sheikh Khalid Ibn el Walîd.