Comparison of Positions determined on the Red Sea with those previously found in Official Marine Surveys.

It is interesting to compare the positions found for certain triangulation points with those determined by the British Admiralty surveyors and by Lieut. Koss, who accompanied the Austrian research-ship “Pola” in 1895-6.[74] The three best defined points of comparison are Berenice temple, the central peak of St. John’s Island, and Halaib Fort. In the case of Berenice and St. John’s Island the observation of the two prior surveys were made at stations a little distance from my triangulation points, but the published charts enable one to scale off the necessary corrections to reduce the positions to those of the triangulated points. At Berenice, the British Admiralty observation point, for which the latitude is given as 23° 56′ 16″, is 1′ 26″ north of the temple, so that the equivalent Admiralty latitude for the temple is 23° 54′ 50″. Similarly Lieut. Koss’s observation point, where the latitude found was 23° 56′ 27″, is 1′ 47″ north of the temple, giving the latitude of the temple as 23° 54′ 40″. My triangulation gives the latitude of the temple as 23° 54′ 39″, thus showing a remarkably good agreement with that found by the “Pola” observer.

At St. John’s Island, owing to the smallness of the scale of the available charts, it is a little more difficult to scale off accurately the Admiralty position for the peak and the reduction to the peak of Lieut. Koss’s point. As nearly as I can scale, the Admiralty latitude for the peak is 23° 36′ 40″, while the point where Lieut. Koss observed his latitude of 23° 35′ 47″, near the south-west shore of the island, is approximately 40″ south of the peak, giving the latitude of the peak as 23° 36′ 27″. I found the latitude of the peak to be 23° 36′ 16″, thus again showing as good an agreement as could be expected, having regard to the fact that it is not easy to scale the latitude of the point much within 10″ from the existing charts.

At Halaib Fort, the Admiralty latitude is 22° 14′ 10″, while the “Pola” expedition found it 22° 13′ 26″, and my triangulation gave the value 22° 13′ 25″. The close agreement between my triangulation value and that observed by Lieut. Koss seems to prove the Admiralty latitude of this point to be some 45″ too high.

Summarizing the latitudes of the three points for comparison we have:—

	Berenice Temple.	St. John’s Peak.	Halaib Fort.
Admiralty Chart	23° 54′ 50″	23° 36′ 40″	22° 14′ 10″
“Pola” Expedition	23° 54′ 40″	23° 36′ 27″	22° 13′ 26″
Ball (Triangulation)	23° 54′ 39″	23° 36′ 16″	22° 13′ 25″

If we make corresponding comparisons of the longitudes of these three points, Berenice Temple, St. John’s Peak, and Halaib Fort, we obtain much more wide divergences, as is only to be expected from the fact that the Admiralty and “Pola” determinations were made by transport of chronometers from Suez, which is over 500 miles distant from Halaib.

For Berenice Temple the Admiralty longitude (obtained by applying the scaled reduction of − 40″ to the observed longitude 35° 29′ 11″ at the observation point) is 35° 28′ 31″. Lieut. Koss’s transport of chronometers from Suez via Jidda leads to a longitude of 33° 30′ 20″ for his observation point, which lies 54″ east of the temple; thus the “Pola” longitude for the temple is 35° 29′ 26″. My triangulation gives 35° 28′ 26″, thus agreeing very nearly with the Admiralty value and differing by exactly 1′ from the value found by Lieut. Koss.

For St. John’s Peak, the longitude scaled from the Admiralty Chart is 36° 10′ 20″. The observations of Lieut. Koss lead to a longitude of 36° 12′ 38″ for his observation point, which is about 35″ west of the peak; thus the “Pola” longitude for the peak is 36° 13′ 13″. My triangulation gives 36° 11′ 42″, being thus between the Admiralty and “Pola” values.

For Halaib Fort, the Admiralty longitude is 36° 37′ 3″, while Lieut. Koss’s figures lead to the value 36° 40′ 38″; my triangulation gives 36° 38′ 56″, thus again showing a value between the two marine determinations.

Summarizing the longitudes obtained for the three points, we have:—

	Berenice Temple.	St. John’s Peak.	Halaib Fort.
Admiralty Chart	35° 28′ 31″	36° 10′ 20″	36° 37′  3″
“Pola” Expedition	35° 29′ 26″	36° 13′ 13″	36° 40′ 38″
Ball (Triangulation)	35° 28′ 26″	36° 11′ 42″	36° 38′ 56″

There can, of course, be no doubt of the immensely greater accuracy of the triangulation method of determining longitude as compared with that of chronometer transport in voyages lasting for months, no matter how many chronometers are carried nor what care is taken in the work. The above differences of longitude are small when one considers that no absolute control of the chronometer of the “Pola” expedition was obtained from October 23, 1895, when the ship left Suez, till its return to the same port on January 27, 1896. If we examine the difference of longitude between points fairly close together, we find rather better agreement between chronometers and triangulation. Thus, for instance, between Berenice and Halaib, a six days’ voyage, we have:—

	Longitude by Chronometers (Koss).	Longitude by Triangulation (Ball).
Halaib Fort	36° 40′ 38″	36° 38′ 56″
Berenice Temple	35° 29′ 26″	35° 28′ 26″
Difference	1° 11′ 12″	1° 10′ 30″

showing an error of only 42″, or about three seconds of time in the six days.

The triangulation-positions:—

	Latitude N.	Longitude E.
Berenice Temple	23° 54′ 39″	35° 28′ 26″
St. John’s Peak	23° 36′ 16″	36° 11′ 42″
Halaib Fort	22° 13′ 25″	36° 38′ 56″

may therefore be taken as practically correct, and the three points may be used as well-determined positions both for further discussion of the “Pola” results and in further surveying expeditions in the Red Sea.[75]

Detail Surveying along Lines of March.

All detail visible along lines of march from camp to camp was recorded on plane-table sheets on a scale of 1:100,000. The usual process was as follows: The plane-table sheet was first provided with a graticule at 10′ intervals of latitude and longitude, and all the triangulation points previously fixed within the area covered by the sheet were marked in their computed places. Stations were chosen along the route at an average distance apart of two or three kilometres, the most commanding hills being selected, and the positions of these were found by plane-table re-section from three or more triangulation points. The compass, being frequently disturbed by magnetic rocks,[76] was only used to get a first approximation to the true orientation of the table. The plane-table station having been fixed on the map, tacheometric readings were taken to all conspicuous points easy of access within a radius of about two kilometres, and plotted at their measured distances along the directions given by the alidade.

In the telemetric measurements a 5-inch tacheometer was used side by side with the plane-table, and two staff-men were employed. As the scale of the map was small, the sights were much longer than is usual in tacheometry, and the maximum distance of 800 metres directly readable by the four-metre staves employed was generally exceeded. For the long distance readings, where the distance between two cross-wires subtended more than the length of the staff, I devised the following process. Bringing the centre wire to the base of the staff, a reading of the vertical circle was taken; next, by the tangent-screw, the wire was brought to the top of the staff, and a second reading of the vertical circle was taken, the difference giving the angle subtended by the four-metre staff. It is clear that the distance is as many times greater than 800 metres, as the angle subtended is less than 17′ of arc, and the distance is thus found by simple proportion.

In the case of very long sights, even this method failed, because the circle could only be read to half-minutes, which was too coarse a graduation to give a good result, and in these cases the method used was one of repetition. The wire being brought to the base of the staff as before, and a first reading of the vertical circle taken, the wire was brought to the top of the staff by the tangent screw, then to the bottom again by altering the levelling screws slightly, again to the top by the tangent screw, and so on, three or four times, and then a second reading was taken on the vertical circle. The slight alteration of level had no sensible influence on the result, and it is obvious that by automatically summing up, say, four intercepts in this way, a very much more accurate value of the subtense angle was obtained than was possible from a single measurement. In practice I found it was best to carry in the waistcoat pocket a card giving the distance corresponding to any number of minutes of difference of reading after a four-fold repetition, and it was quite practicable to measure up to three kilometres of distance within one hundred metres of the truth; as this only represented a millimetre on the sheet, and as, moreover, errors were not cumulative, owing to the independent fixation of each successive station by re-section, the accuracy was all that could be desired, and the rapidity of measurement was very great. In this long distance type of tacheometry, finely graduated staves were of no use; the form of staff employed was a broad-faced one, fifteen centimetres wide, bearing fifty-centimetre divisions painted alternately black and white right across the whole breadth of the staff.[77]

An average of about six or eight conspicuous points having been telemetrically fixed from a station, the detail was sketched in around them, and other more distant points were at the same time fixed by plane-table intersections from several stations. At the stations the pencil sketching of relief was by form-lines which were subsequently replaced by hachure-rendering when inking up the sheets in camp.

Occasionally, when a high hill-station was employed overlooking a long wadi, time was saved by reading only two distances, both in the same wadi, one very near to the station and the other two or three kilometres away, at the same time observing the depression-angles to these points. The slope of the wadi being found in this way, the depression-angles to intermediate points gave the distances of such points without the necessity of staff reading at the intermediate points at all. Thus, suppose the near point was close under the station, with a distance of 500 metres and a depression-angle of 18°, while the remote point up the wadi had a distance of three kilometres and a depression-angle of 2° 30′. By means of a slide rule or three-figure logarithms, the near point was found to be 163 metres below the station, and the distant one 130 metres. A point in the wadi estimated roughly as half way between the two would be about 146 metres below the station; so that if the observed depression-angle to it was, say, 4° 40′, its distance would be 146tan 4° 40′, or 1·8 kilometres. Any possible error of preliminary estimation of the distance in order to find the level would be without sensible influence on the resulting true distance.

The process of traversing between stations was seldom resorted to, as the method of fixing stations by re-section from triangulation points is much more accurate (the errors not being cumulative) besides being more rapid. But in certain tortuous cañon-like wadis, where great and time-consuming climbs would have had to be undertaken in order to see any triangulation points, the method of traversing with the tacheometer had to be employed.

Levels along the line of march were measured trigonometrically whenever possible; the vertical angles to one or more triangulation points being read with the tacheometer, and the distances scaled off the map, the differences of height, corrected for refraction, were found by the slide rule in the same manner as in the triangulation already described. Heights of passes and camps whence no triangulation points were visible were determined by barometer-comparisons between them and points of precisely determined altitude.

Names of places were written down by the guides in Arabic characters on the spot where they were ascertained, and transliterated on the Egyptian Government system for insertion in the map. Most of the place-names were checked by getting the guides to give them from several different stations.

Detail Surveying at Occupied Triangulation Stations.

It was generally necessary to remain for at least a week on the mountain summits which formed the main triangulation stations, for only on about one day in seven was the air clear enough for sighting the beacons on the longer lines. Occasionally the entire landscape was blotted out for ten or more consecutive days by clouds surrounding the summit, while at other times it was possible to see only for a limited distance round the station owing to haze. Such times were made use of to map all visible detail within a moderate range (say within a radius of twelve kilometres) round the station.

In this work the first stage was to find a small base, one end of which was the station itself. Usually a minor peak of the same range, 500 to 1,000 metres away from the station, was fairly easily accessible, and was chosen for the other end of the base. The six-inch theodolite being at the main station, the five-inch tacheometer was set up at the auxiliary station, and all noteworthy hill tops, as well as a few points along each main line of drainage, were triangulated off this small base. The length of the base was found by including one or two main triangulation points in the round of angles. These minor triangles were conveniently reduced by the slide rule, and the points plotted at once on the plane-table by means of the alidade and the calculated distances. The base being short, it was necessary to observe to fine marks; cracks in the rocks, and the droppings of birds on the peaks, and the centres of selected tree trunks in the wadis, were usually chosen. The levels of these minor points were determined by vertical angulation in the ordinary way. Usually about thirty points were thus fixed round each high station. Once a number of points were fixed in the wadis, the levels of these gave the slope, and the difference of height between any other parts of the wadis and the station could be estimated to within a few metres by means of the knowledge thus obtained. A sketch being now made of the wadis, which appeared spread out almost like a map below the station, a hundred or more points along them were selected, and their depths below the station being very approximately known from the wadi slope, their distances were found by observing depression angles to them and reducing the vertical triangle by means of the slide rule on the spot. In all, therefore, measurements were usually made of the distances of from 100 to 200 conspicuous points in the area round the station, and when these were plotted with the alidade on the plane-table sheet it was not difficult to sketch in all the detail with considerable accuracy. Usually it was not possible to see all round the mountain from the station itself, so that subsidiary plane-table stations near the main one were necessary. In other cases more than one small base was measured in order to get good angles to various points by the minor triangulation.

By the combined use of minor triangulation for peaks, and vertical angulation for points situated along drainage lines, it was found that far more sketching could be done in a few days at a main station than would have been possible in the same time by tacheometric work on the lower ground, and that of greater accuracy. More than half of the entire detail sketching was in fact done at the main stations.

Survey of the Coast-line.

In the earlier portion of the work, i.e., north of latitude 24°, the work on the coast-line was confined to the fixation of prominent points such as spurs and tips of islands. Some of these were fixed as intersected points during the triangulation, while others were determined by observing the depression angle and azimuth to them from trigonometrical stations of known altitude. In this latter method, taking the mean coefficient of refraction as 0·13, the formula[78] employed was

where d = distance in metres, θ = depression angle in seconds, and h = altitude of station in metres. This formula is rather tedious to work out, though the work is relatively not so great if a number of points are to be calculated from observations at the same station. Prominent points having been fixed in this way, the coast-line north of 24° was sketched in from the Admiralty Chart, adjusting the longitude to fit the points fixed.

It was sometimes a little difficult, however, to identify the fixed points on the existing charts, and hence I tried to find some process of surveying the entire remaining coast-line de novo in detail. Traversing along the coast was placed out of question by the great expenditure of time and money which it would have entailed. Eventually I was led to devise a new method, by which long stretches of coast-line could be mapped by polar co-ordinates from mountain stations with great speed and accuracy. The directions of a series of points sufficiently close together along the coast were taken by theodolite, and the depression angles simultaneously observed with the vertical circle. Then, instead of computing the distances to the points, they were plotted by a special scale graduated directly in angles of dip; by thus doing away with all calculation at the station, it was possible to lay down the points on the chart as fast as the observations could be taken, usually at the rate of four or five points a minute, and it was frequently possible to map thirty kilometres or more of coast-line in an hour with great accuracy. As I have given a full account of this new method in a separate publication,[79] I shall not go into it further here, but would refer those interested to the publication just mentioned.

With the aid of the new method the entire coast-line from just north of Ras Benas southwards to the parallel of 22°, a distance of over 200 miles, was mapped in detail on the 100,000 scale. I had frequent opportunities of testing the accuracy of the delineation of the coast, both by mapping the same stretch from two widely-distant stations of different heights, and by subsequently surveying small portions of the coast directly by plane-table and tacheometer from triangulation points on or near the coast; and in all cases I found the accuracy to be very high, the differences found rarely exceeding the thickness of a line on the map. The tides in the Red Sea are so small in range (generally only about a metre) that variations of sea-level were practically negligible during the operations. Bearing in mind the great difficulties attending the survey of so inhospitable a coast by the ordinary method of traversing, I believe the resulting outline of the coast on my maps is very much more correct than that shown on any previous charts. An accurate delineation of the coast-line in this region is of course chiefly of value as indicating the extent of land; it is of little importance to the navigator, for whom the positions of the outlying dangerous reefs, mapped by the Admiralty surveyors, are far more important.

Location of the Administrative Boundary between Egypt and the Sudan.

By an Arrêté of the Ministry of Interior issued in 1902 it was enacted that the boundary between the administrative divisions of Egypt and the Sudan should be as follows:—

Commencing at Bir Shalatein on the coast of the Red Sea, the limit runs to Bir Meneiga, thence to Gebel Niqrub, thence to Gebel Um el Tiur and to Deiga. From Deiga the line continues to Bir Esmet Omar, thence to Gebel Bartazuga, and finally to the Nile at Korosko.

This frontier was defined after a commission had sat, at the Mudiria of Aswân, to make enquiries as to the vested rights of the Bedouin tribes, the guiding principle being that all Bisharin tribes should be under Sudan administration, and all Ababda tribes (with one exception) under the Government of Egypt. A map accompanied the decision, but was of a very rough character, and the positions of the points specified were not known within several miles.

Part of my work comprised the precise fixation of the points specified in the Arrêté, with a view to laying down the boundary accurately on a map. As was natural in the case of a boundary settled without careful reference to the ground, certain difficulties arose in the location. In the first place, there are two distinct Gebels Niqrub, and two distinct Gebels Um el Tiur. I assumed the higher mountain of each pair to be the one indicated. Secondly, the precise point of the mountain was unspecified; I assumed the highest peak to be the point referred to. Thirdly, the text of the Arrêté disagrees with the map accompanying it, in that the map shows the line curved to pass close to Gebel Mishbih, which is not mentioned in the Arrêté. I assumed the text of the order to be determinative, and that between the points specified the limit followed great circles on the globe, i.e., practically straight lines on the map. The locality called Deiga was not visited, and can only be approximately fixed; it is said by guides to be a narrow road near Gebel Muqsim, of which mountain several peaks were fixed by triangulation.

The following table gives the positions found for the various points along the boundary from the sea to the meridian of 34° (1) from my survey operations, and (2) as scaled from the map accompanying the Ministerial Arrêté. A comparison of the two sets of positions will show how much the survey has added to our knowledge of the geography of this part of the desert.

Point.	Latitude N.		Longitude E.
	From my Survey.	From Arrêté Map.	From my Survey.	From Arrêté Map.
Bir Shalatein	23°  8′  5″	22° 39′  0″	35° 36′ 28″	36°  2′ 30″
Bir Meneiga	22° 47′  8″	22° 41′ 30″	35° 12′ 20″	35°  2′ 30″
Gebel Niqrub (El Foqani)	22° 51′ 29″	22° 48′  0″	34° 56′ 48″	34° 51′  0″
Gebel Um el Tiur (El Foqani)	22° 17′ 54″	22° 18′ 30″	34° 41′  1″	34° 32′  0″
Deiga (approx.)	22° 10′  0″	22°  9′  0″	34°  1′  0″	34°  3′  0″

Variation of the Compass.

Careful observations were made of the variation of the compass at three stations, viz., Berenice Temple, Abu Saafa Springs, and near Halaib Fort,[80] these three points being selected as being well-known places and at the same time likely to be free from local magnetic disturbance. Berenice is on the coast-plain where only coral and sand occur; Abu Saafa is in a sandstone district about 100 kilometres south-west of Berenice, and Halaib is on the calcareous and gypseous rocks of the coast about 220 kilometres south-east of Abu Saafa.

The instrument used was a five-inch theodolite fitted with a good trough compass. A lens was used to bring the needle accurately to zero, and the sun or a star was employed to find the true meridian. In each case several observations, each with an independent setting of the needle, were made, and the mean taken. The values obtained were:—

Place.	Date and Time.	Compass-Variation West.
Berenice Temple	January 6, 1907, 5·30 p.m.	2° 44′
Abu Saafa Springs	October 25, 1907, 4 p.m.	2° 37′
Near Halaib Fort	May 7, 1908, 10 a.m.	2° 18′

In order to find to what degree of accuracy the results of these determinations might be relied on, the instrument used was tested against the Kew magnetometer at the Khedivial Observatory, Helwân, after the completion of the work. Three observations for the declination at Helwân gave the westerly variation as

	2° 41′·2
	2° 58′·8
	2° 55′·0
Mean	2° 55′·0

while the true declination as given by the Kew magnetometer at the same time was 2° 52′ 5″. Thus it appears reasonable to believe the observed values to be within about 5′ of the truth.

It is rather curious to note that the declination observed at Abu Saafa is less than that at Berenice, which lies further east, even if allowance is made for the secular change in the interval. The difference from what one would expect is, however, possibly owing to errors of observation of the magnitude above-mentioned, or it may be due to a slight local influence of magnetic rocks underground at Abu Saafa, where the ground is near to the base of the Nubian sandstone beds, which rest presumably on eruptive and metamorphic rocks.

It is interesting to compare the observations of declination at Berenice and Halaib with those recorded by Rossler[81] at the same places in 1895. Thus we have:—

Berenice.		Mersa Halaib.
Rossler, Nov. 27, 1895	3° 54′	Rossler, Nov. 18, 1895	3° 36′
Ball, Jan. 6, 1907	2° 44′	Ball, May 7, 1908	2° 18′
Diff. in 11·1 years	1° 10′	Diff. in 12·5 years	1° 18′
Yearly decrease	6′·3	Yearly decrease	6′·3

We thus arrive at a yearly secular diminution of declination of 6′ 3″, confirming the value arrived at by Mr. Keeling[82] for the rate of secular change in the Red Sea area from a comparison of other observations. It may be therefore concluded that the rate of 3′ per annum given in the “Admiralty Pilot”[83] is only about half the true value.

Travellers in the Eastern Desert should exercise care in the reliance they place on compass bearings. Bearings taken with a compass are generally normal in granite and sandstone country; but wherever dark igneous and metamorphic rocks abound, disturbances are likely to occur. Local deviations of 5° to 10° are quite common, and in some serpentine areas even 40° of disturbance may be observed. In some places, one can deflect the needle through a large angle by means of a fragment of the rock no larger than a nut, so rich are some of the basic rocks in magnetic minerals. Some lumps of rock even show strong polarity, attracting or repelling the north pole of the needle according as one part or another of the lump is presented to it.

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CHAPTER IV.

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THE WADIS DRAINING WESTWARDS TO THE NILE.

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It has been already mentioned (p. 21) that all the drainage westward from the main watershed ultimately reaches the Nile by the three great trunk Wadis Shait, Kharit, and Alaqi. In the present chapter a detailed description will be given of those parts of these wadis and their tributaries which are known within the area under discussion. The following scheme shows the relations of the principal tributaries, important feeders of the tributaries themselves being indicated in (brackets):—

			Wadi Dweig.
Wadi Shait			Wadi Muelih (Wadi Gerf, Rod el Ligah, Wadi Sibrit).
			Wadi Hamish.
			Wadi Hilgit (Wadi Um Hasidok, Wadi Um el Tiur).
			Wadi Egat.
			Wadi el Anbat.
			Wadi Abarun.
			Wadi Um Daba.
			Wadi Abu Argub.
			Wadi Safihat.
			Wadi Um Sellim.
			Wadi Medsus.
Wadi Kharit			Wadi Abu Gurdi.
			Wadi Elemikan (Rod el Geneina).
			Wadi Abu Hashim.
			Wadi Helie.
			Wadi Abu Hamamid (Wadi Marasani, Wadi el Sheikh).
			Rod el Kharuf (Wadi Abu Had).
			Wadi Khashab (Wadi Metawit, Wadi Antar).
			Wadi Garara (Wadi el Kreim, Wadi Timsah, Wadi Ghadrib, Wadi Abu Hashim, Wadi Abu Homur).
			Wadi Natash.
			Wadi Himeitra.
			Miti Kwan (Wadi Duag, Wadi Kirir, Wadi Merau, Wadi Miaus).
			Wadi Dageina.
			Wadi Alfawi.
			Wadi Egat (Wadi Hiteib).
			Wadi Hateib (Wadi Suhin).
Wadi Alaqi			Wadi Guqub.
			Wadi Um Teneideb.
			Wadi Defeit (Wadi Sarid, Wadi Dauriai, Wadi Hamida, Wadi Bint el Feqoh, Wadi Anweiyib, Wadi Meladoyeb, Rod Hawanin, Wadi Bagharid).
			Wadi Eleifat.
			Wadi Seiga (Wadi Um Derera, Wadi Abu Had, Wadi Um Gholqa).

Most of the drainage-lines mentioned in the description will be found marked on the orographical map which forms Plate I; but the scale of that map is too small for all the minor feeders to be indicated with clearness.

Wadi Shait, an important main trunk wadi draining westwards to the Nile, originates at the west foot of Gebel Ras Shait, in lat. 24° 50′, long. 34° 31′, and joins the Nile Valley a little to the north of Kom Ombo. It has a total length of very nearly 200 kilometres, and an average fall of three metres per kilometre. The fall is much more rapid in the upper reaches than lower down; in the first fifty-five kilometres of its length, from the foot of Gebel Ras Shait to Bir Um Gubur, the fall is 340 metres, or an average gradient of six metres per kilometre, while from Bir Um Gubur, for the remaining 140 kilometres of its course, its fall is only 250 metres, or an average gradient of less than two metres per kilometre.

The head of Wadi Shait is formed by the union of a number of drainage channels from a kind of cul-de-sac formed by Gebels Migif, Ras Shait, and Mudergeg, where it is separated from the heads of Wadi Gerf and Wadi Hafafit by flat sandy divides. Passing in a south-westerly direction to the west of Gebel Migif and Gebel Dweig, it receives as a tributary Wadi Dweig (in which are the ruins of an ancient station) on the left. Taking thence a more westerly course it traverses more open country, and then narrows among hills north-west of the remarkable peak of Gebel Abu Khrug. At a bend further on is Bir Murra, a shallow well sunk in the alluvium of the wadi floor at the foot of a serpentine scarp; the water here (as the name of the well indicates) is very bitter, and is generally drunk only by camels. After passing Bir Murra, the wadi turns south-west, then curves again near Bir Um Gubur, about three kilometres south-east of Gebel Sufra, and about twelve kilometres below Bir Murra. Bir Um Gubur is a shaft about two and a half metres diameter, sunk about eight metres deep in the alluvium of the wadi; it was yielding good supplies of excellent water in 1906. About ten kilometres below Bir Um Gubur, Wadi Hamish joins Wadi Shait from the north-east. In the remainder of the course of Wadi Shait to the Nile, the principal water source is Bir Heliwat,[84] about ten kilometres below the point of influx of Wadi Hamish, and the chief tributary wadis are Muelih, Beza, and Midrik, all of which join it from the north-east.

The upper portions of Wadi Shait contain a fair abundance of trees and scrub, but the lower parts are sandy arid wastes.

Wadi Muelih originates in the mountain called Gebel Iteima, in lat. 25° 8′. For about sixteen kilometres its course lies ill-defined over a sandy plain with scattered low hills, to Erf el Fahid, a remarkable east and west quartz ridge nearly two kilometres long rising among crushed diorites and schists to a height of 579 metres above sea, or ninety-five metres above the wadi, in lat. 25° 0′. After passing Erf el Fahid, the course of the wadi changes to south-west, and gradually becomes more enclosed by low hills. The first hills passed on the right are high ridges formed by great quartz veins striking south-west, at the foot of which the wadi forms a plain nearly a kilometre broad, with low hills and mounds of dark gneisses and schists on the left. At ten kilometres below Erf el Fahid, on the left of the wadi, is a horse-shoe shaped hill of aplite called Marwot Rod el Ligaia, to the north and south of which are other hills penetrated by networks of quartz veins. Two kilometres further on, a band of diorite gneiss cuts across the wadi, which then commences to narrow in among hills of crushed diorites, grey gneisses, and schists, with many dykes of porphyrite and felsite. These hills become progressively higher as one descends, and near the meridian of 34° the wadi curves round the foot of Gebel Muelih, a great bare white granite boss rising through darker rocks to a height of 330 metres above the wadi, or 707 metres above sea. Just after passing Gebel Muelih the wadi, which has here a width of only some 200 metres, turns south-west again. At this turn, nearly in the centre of the wadi floor, is Bir Muelih, an excavation about six metres deep in the alluvium, yielding very salt water drinkable only by camels. North-east of the well a track strikes over the hills towards Dungash mine. From Bir Muelih the wadi continues in a roughly south-west direction past Bir Samut (well about one kilometre north of Wadi Muelih) and then takes a more southerly course draining into Wadi Shait in longitude 33° 46′.

The wadi floor falls from a level of 484 metres near Erf el Fahid to 375 metres at Bir Muelih, the length of the wadi between the two places being about twenty-seven kilometres; this gives an average fall of about four metres per kilometre; the actual gradient varies from about two metres per kilometre in the broader portions to over six metres per kilometre in the more enclosed parts of the wadi.

The upper parts of Wadi Muelih are barren and sandy, but the lower portions contain a fair amount of vegetation. The principal feeders of Wadi Muelih are Wadi Gerf, which enters by several openings on the left above Gebel Muelih, Wadi Samut, entering on the right in long. 33° 54′, and Wadi Sibrit, entering on the left in long. 33° 50′.

Wadi Gerf is the collective name given to a number of rather complicated drainage channels forming tributaries to Wadi Muelih. The principal heads are to the east and west of Gebel Nugrus. The eastern head is called Wadi Hangalia; it commences at about an altitude of 811 metres due east of the highest point of Gebel Nugrus, at a difficult pass leading over the main watershed to Wadi el Nom, and curves round the north spurs of Gebel Nugrus to join the western head. In the Wadi Hangalia are some old ruins of a mining camp, and also some recent prospecting workings and a well giving a poor supply of water. The Western head of Wadi Gerf commences in nearly level ground on the main divide west of Gebel Nugrus, at an altitude of 691 metres. These two main heads unite close to the east of Gebel Ras Shait, whence Wadi Gerf courses about north-west through low hills. A third head is in lat. 24° 52′, at a pass leading into Wadi Um Khariga. A fourth, called Rod el Atut, takes the drainage from all sides of the conspicuous black cone of Gebel Atut. A fifth, called Rod Um el Farag, drains from the mass of moderately high hills further west called Um el Huetat; these hills contain some old mines, chiefly in talc schists. The drainages from these various heads all eventually take a west-south-west course among low hills and over a sandy plain and enter Wadi Muelih by several openings near longitude 34°. Minor tributaries are Wadi Abu Seyal and Wadi Um Seyal, south-east of Gebel Atut, Rod el Ligaia, in longitude 34° 10′; and Rod el Ligah, in latitude 24° 50′.

The principal hills of the plain over which Wadi Gerf and its tributaries run their course are some very remarkable small black peaks collectively called Khusa el Faraon, a light coloured hill called Marwot Rod el Ligah, and a ridge called Erf el Sagur; these two last rise to 514 and 523 metres above sea-level respectively.

Wadi Gerf possesses a fair amount of vegetation, except where it meanders over the sandy plains; in the tributaries Wadi Um Seyal and Wadi Abu Seyal acacia trees are specially numerous.

Wadi Sibrit is a long narrow wadi following a course somewhat south of west, originating to the west of Gebel Mudergeg and joining Wadi Muelih in longitude 33° 50′. It possesses many trees and a good well, Bir Sibrit. This latter is an excavation in the wadi floor, in longitude 33° 58′; it is said to yield a constant supply. In the spring of 1906 I found the water was at a depth of eight metres below the surface, and of good quality.

Wadi Kharit, one of the greatest trunk wadis of Egypt, has its principal head at Gebel Ras el Kharit, on the main watershed in latitude 14° 10′ and longitude 35°. Pursuing a course the prevailing direction of which is a little north of west, and collecting the drainage from numerous great wadis on its way, it debouches on the Kom Ombo plain and reaches the Nile at the same point as another great wadi, Shait, in latitude 24° 35′. The length of the main channel is over 260 kilometres, and of its tributaries probably more than twenty times as great. It drains an area of more than 23,000 square kilometres. Its average fall is about two metres per kilometre, but in its lower reaches its gradient is less than half this amount.

The principal tributaries of Wadi Kharit, which will be separately described, are the Wadis Natash, Antar, Khashab, Abu Hamamid, Elemikan, and Garara (this last with Wadis Timsah and Ghadrib as great feeders). I now propose to trace out the course of the main wadi in some detail, leaving its greater tributaries for separate description, but including its minor feeders.

The main head of Wadi Kharit is on the Nile-Red Sea divide, between Gebel Ras el Kharit and Gebel Mikbi, at an altitude of considerably more than 600 metres above the sea. The wadi at first courses a little south of west, over a gently falling sandy plain with hills of bouldery granite, and curves round the south spurs of Gebel el Anbat.[85] Here it receives two tributaries, one from the north-west called Wadi Hilgit, and one from the south-east called Wadi Egat.[86]

Wadi Hilgit originates on the main watershed in longitude 34° 52′, near Gebel Um Usher. A very steep and difficult pass over the watershed separates its head from that of another Wadi Hilgit draining northward to Wadi Huluz. The two wadis are called Wadi Hilgit lil Kharit and Wadi Hilgit lil Huluz respectively when it is necessary to distinguish them. On its course southward to Kharit, Wadi Hilgit receives as tributaries Wadi Um Hasidok and Wadi Um el Tiur, draining the mountains of the same names.

Wadi Egat drains part of the west slopes of Gebel Abu Gurdi and the south part of Gebel Egat, for the first half of its course being shut in by high hills and for the latter half passing over a gently falling plain.

After passing Gebel el Anbat, Wadi Kharit continues its course a little south of west, in broad shallow drainage channels over a great sandy plain. In this part of its course it receives many important feeders from the mountain masses which limit the plain to the north. The principal of these feeders are the Wadis Anbat, Abarun, Um Daba, Abu Argub, Safihat, Um Sellim, and Medsus. Near where Wadi Medsus enters, Wadi Kharit takes a more southerly course, passing north of a mass of low dark hills called Gebel Geneina, and here it receives Wadi Abu Gurdi, draining the west slopes of the mountain of the same name, the ill-defined Wadi Elemikan (see p. 84), draining the extensive plain south of Gebel Abu Gurdi, and the Rod el Geneina, draining from the hills of Geneina. A little further on, curving to the north-west, it receives Wadi Abu Hashim and Wadi Abu Selili, which drain the south flanks of Gebel Kahfa.

The next feeder is the Wadi Helie, which drains the west slopes of Gebel Kahfa and enters Kharit from the north-east; a well, Bir Helie, exists in this wadi about eight kilometres above its junction with Kharit. The well appears to be of the same character as Bir Abu Hamamid; it was yielding plenty of good water in the spring of 1906, but in the autumn of the same year the supply was said to be smaller and rather salty.

About ten kilometres below the point of influx of Wadi Helie, Wadi Kharit receives Wadi Abu Hamamid (see p. 85), coming from the north-east, and some fourteen kilometres further on another tributary, the Rod el Kharuf, enters from the opposite side conveying the drainage from the north-west flanks of Gebel Zergat Naam.

In the remaining portion of its course to the Nile, Wadi Kharit receives numerous other tributaries, of which the principal are Wadi Khashab and Wadi Antar on the north, and the Wadi Garara on the south (see pp. 86 and 87).

On the whole, Wadi Kharit is poor in vegetation; trees are fairly abundant in the central portion of its course, but both near its head and near the river it is very barren. In consequence of its sandy and arid character near the Nile, it is not usual for caravans to journey along the wadi from its mouth; Arabs from Daraw usually go up the tortuous and sandy Wadi Allawi, and thence enter Kharit either by the Rod Abu Modellim or by a track among hills which leads eastward to Bir Qoleib. Bir Qoleib is a good well in a small tributary of Wadi Kharit, about seventy kilometres by road from the Daraw. From Bir Qoleib to the wells of Abu Hamamid and Helie the westward journey is about 110 kilometres, while from Bir Qoleib to the well of Abu Hashim, south-east (on the road to Abu Saafa), is a distance of about seventy-five kilometres.

Wadi Elemikan is the name given to an ill-defined system of drainage channels meandering over the plain south of Gebel Abu Gurdi. It originates on the main watershed, and at its head there is a very easy pass over into the Wadi Lahami, which descends to the sea. At this point, which is 590 metres above the sea, the watershed is ill-defined, being a sandy plain; but while to the west the plain continues with only a slight fall, to the east it soon gives place to rugged country through which narrow wadis descend rapidly towards the sea coast. The plain west of the watershed is remarkable for the presence of three great bosses of quartz, the largest of which, called Marwot Elemikan, rises as a conspicuous cone of dazzling whiteness to a height of sixty-eight metres above the plain. Besides the drainage from the plain itself, Wadi Elemikan receives feeders from the hills which flank Gebel Abu Gurdi to the south, and also a portion of the drainage from the Wadi Abu Gurdi, which divides into two channels on emerging from the mountains. Passing between the granite hills of Gebel Abu Derega and Gebel Selaia, Wadi Elemikan courses a little north of westward over a great sandy plain to join the Wadi Kharit north of Gebel Geneina in longitude 34° 36′. It is a barren wadi, but water can sometimes be obtained a little north of it at a small spring called Megal el Selaia, at the foot of a low hill one kilometre south-east of the great rounded granite boss of Gebel Selaia. I obtained a small supply of very good water here early in 1906, but the spring is a very slow one and is said to fail altogether in dry seasons.

Wadi Abu Hamamid, an important tributary of Wadi Kharit, originates as a series of gullies in the mountains of Gebel Abu Hamamid, on the west face of the main watershed, in longitude 34° 48′. It courses, among high hills a little north of west to longitude 34° 41′, then turns south-west and enters the plain which extends to the west of Bir Shadli. Here it receives part of the drainage from Wadi el Sheikh, and turns westward among lower hills, passing north of the red hills called El Hamra, to Bir Abu Hamamid, and then turning south-west between El Hamra and Hamrat Mukbud to join Kharit in longitude 34° 23′.

Bir Abu Hamamid is an important well; it is a rude irregular excavation, about six metres deep, in the wadi floor, down which men can walk to fill their water skins. This well was yielding more plentiful supplies in the autumn of 1906 than any of the other wells in the neighbourhood; the water was rather salty and muddy, but quite drinkable.

From near Bir Abu Hamamid, a track leads north-westward over the hills to Bir Khashab and on to Bir Masur. To reach Bir Shadli, one follows up the Wadi Abu Hamamid till it opens on to a plain, and then strikes almost due eastward across the plain.

A small tributary which joins Wadi Abu Hamamid from the north-east, in longitude 34° 41′, called Wadi Marasani, is important as leading to a pass over the main watershed into Wadi Marasan, a tributary of Wadi Huluz. The altitude of the pass is 685 metres above sea; it is quite practicable for baggage camels.

Wadi el Sheikh, the only great tributary of Wadi Abu Hamamid, originates in longitude 34° 40′, in the hilly tract west of Gebel Abu Hamamid. In the upper part of its course, it is a narrow winding wadi, mostly shut in by high hills, pursuing mainly a direction a little west of south, fed by numerous lateral wadis entering from among the hills to the east, of which the principal are the Wadis Um Somra, Krioni, Um Nasir, Um Hereini, Um Sereiha, Um Deheisi, Um Retba, and Um Hargal. Near the point where Wadi Um Deheisi joins it, the Wadi el Sheikh emerges from the hill country and meanders over a plain. At its entry on to the plain is the tomb and well of Sheikh Shadli, views of which are given on Plate V. The tomb, from which the wadi derives its name, is a white domed structure, tended by a Moorish guardian. The Ababda Arabs hold the memory of Sheikh Shadli in high veneration, and make yearly pilgrimages to his tomb. The well, Bir Shadli, close to the tomb, is a shallow excavation in the stony alluvium of the wadi floor. Here there is a perennial supply of water, which, however, varies much in quality and quantity; after rain, there forms a large pool of good water, the surface being maintained almost level with the ground by underground influx; while when there has been no rain for a year or more the water is only found by digging to several metres depth, and then only infiltrates slowly at the bottom of the hole, the quality simultaneously falls off and the water acquires a saline and purgative character.

After passing Bir Shadli and entering on the plain, Wadi el Sheikh splits up into numerous channels, one of which joins the Wadi Abu Hamamid, while the others continue in a south-westerly direction, fed by the Wadis Um Retba and Um Hargal, draining from the north flanks of Gebel Kahfa. Uniting together as they leave the plain to re-form a single Wadi el Sheikh, these drainages turn westward among the hills to join the Wadi Abu Hamamid.

Bir Shadli is one of the best-known centres of the Ababda Arabs. Though there is no permanent settlement, it is seldom that many days elapse without Arabs coming to the place to water their animals, which graze in the adjoining wadis. Many roads converge here. To the west, a track leads to Bir Abu Hamamid. To the north-east, a track leads up the Wadi Sheikh, across Wadi Abu Hamamid, and by an easy pass near Gebel Marasan over the main watershed into Wadi Huluz. To the south-east there are several alternative routes by which one can journey over easy passes north of Gebel Kahfa on to the plain of Selaia and down the Wadi Lahami to Berenice. Yet another road leads a little west of south across the Wadi Um Hargal, and by an easy pass into Wadi Helie, a small tributary of Wadi Kharit which drains the west side of Gebel Kahfa, and in which there is a well of similar character to that of Abu Hamamid.

Wadi Khashab commences its course near Gebel el Heda, a little east of longitude 34° 30′, and continues in a generally south-west direction to the latitude of Gebel Hamrat Mukbud. Here it takes a westerly course, passing south of Gebel Homr Akarim and entering Wadi Kharit from the north in about longitude 33° 49′. Wadi Khashab receives its name from its relatively well-wooded character; in its upper parts it presents the appearance of a broad valley, in which trees are so numerous as to give a very pleasing contrast to the dreary wastes on either side of it. Bir Khashab is a series of pits sunk in the wadi floor in about longitude 34° 23′, which were yielding small supplies of water in 1906.

The principal feeders of Wadi Khashab are Wadi Metawit and Wadi Antar. Wadi Metawit is a short valley originating near Gebel Metawit, and joining Wadi Khashab a short distance above Bir Khashab. It possesses an important well, Bir Metawit, excavated about eight metres deep in the centre of the wadi floor, about three kilometres north-north-west of the summit of Gebel Metawit, on a road leading south-east from Bir Masur to Bir Shadli. This well, near which are some large acacia trees, was yielding a plentiful supply of excellent water in the spring of 1906.

Wadi Antar originates near the hills of Nukheira and El Heda, and courses westward as a very wide shallow sandy depression south of Gebel Um Goraf. At the foot of Gebel Derera it turns southward, receiving the tributary Wadi el Anz from the left a little further on; it turns again westward and then north-west to near Gebel Muktil, beyond which it courses south-west and joins Wadi Khashab in longitude 33° 55′, a short distance only above the point where that wadi enters Kharit.

Wadi el Garara, the great southern tributary of Wadi Kharit, heads on the main watershed east of Gebel Um Harba. Pursuing at first a north-westerly course over a sandy plain, it emerges between two high sandstone hills ten kilometres north of Gebel Um Harba, and turns somewhat more to the west, receiving the Wadi el Kreim, which drains the south-east flanks of Gebel Zergat Naam. A little further on it receives an unnamed tributary which courses north-westward from Gebel Um Harba as a great valley nearly full of blown sand. Still further on its course it is fed by another unnamed tributary which, coming from the main watershed in latitude 23° 30′, courses over a wide sandy plain north-westwards. This latter tributary is very barren, but is of some importance as forming a very easy though sandy road over the main watershed to the Wadi Arned (which leads to the springs of Abu Saafa) and as passing, about five kilometres before reaching the pass, a well known water-hole called Galt el Aguz. This galt is a huge sandstone basin in the hills on the east side of the road, fairly easy of access. After rain it holds an immense supply of water, but owing to the porous nature of the sandstone it becomes dry in a few months of drought; rude Greek inscriptions on the rocks, mixed with spirited drawings of animals, show that this source of water supply was known and used in Ptolemaic days. Besides the drainage from the pass, the tributary first mentioned takes that from the sandstone hills of Um Khafur situated further east.

A little lower down, Wadi Garara receives feeders from the north-east, draining the hills round Gebel Nikeiba and Gebel Felieiti, and then the long Wadi Timsah coming from the south.

Wadi Timsah heads among high granite hills a little north of latitude 23°, and courses in a nearly northerly direction for nearly ninety kilometres to join Wadi Garara. The prevailing character of Wadi Timsah itself is sandy and dreary, but its feeders from the eastern hills are richer in vegetation, and in years when there is rain they furnish in their upper portions good grazing ground for Arab camels. The principal of these feeders, enumerating from the south northwards, are the Wadis Um el Rid, Awamtib (with Wadi Um Marakh), Shabakhit, and Dagalai. All these drain the western parts of the high sandstone hills called by the same names. Water can be got from galts here after rain. Near the head of Wadi Um el Rid, there is a very easy pass over the main watershed into Wadi el Dreb, which leads to the well of Um Reit.

Of the Wadi Ghadrib, which heads near the hills of Gebel Abu Rahia and Gebel Um Rewat, in latitude 23°, and follows a course roughly parallel to, but a few kilometres west of that of Wadi Timsah, not very much is known. Its prevailing character is sandy and arid.