210 Bayuda Desert.

Abu Klea or Tleh wells.

Shebakat wells.

Meteuima.

Rkiny MAaon.

Water.

Sinking wells.

Jebel Gilif.

is driven to the apex, whence, falling over and remaining at its natural angle of repose on the concave side, the hill gradually but surely advances, the highest of the sand hills in this locality are about 13 feet high, their rate of progress depending entirely on the strength of the wind ; to a camel they are no obstacle as it winds amongst them at will.

At 150 miles from Ambugol are the wells of Abu Klea, or strictly speaking Abu Tleh (Tleh equals a particular kind of grass), artificial pits of similar character to those already described ; the water is good and rarely fails ; they require of course frequent cleaning out.

At Shebakat, near the 168th mile, is a large well about 12 feet in diameter, sunk to a depth of 50 feet through the sandstone to a bed of water-bearing gravel ; the water is brackish but the supply perennial.

At 175 miles from Ambugol, Metemma is reached ; the town is about 1 mile from the Nile, but the plain between is occasionally flooded. The water supply is from welh kept up by percolation from the river, and is therefore excellent.

Hence to Khartoum, as stated above, the river is navigable for nearly the entire year, vide Chap. X. The rainy season in the Bayuda Desert is uncertain, as this is the extreme northern range of the tropical monsoon ; there may be showers in May, but the true rains fall in June, July, or August. Some years may pass without any at all, and then a perfect deluge floods the country and refills the pools and wells.

The conformation of the Jebel Gilif is such, that notwithstanding the large amount of water running off during the rains, a considerable quantity is stored at high levels, gradually finding its way into the sand-filled wadis, through permeable granite angites and diorites, of which Jebel Gilif is composed.

These wadis are crossed at intervals by spurs of trap rock, that serve the double purpose of keeping up the level of the wadi, which would otherwise rapidly degrade, and of affording, so to speak, " artesian " vents, up which the water, confined between the beds of the " Nubian " sandstone below, finds its way into the loose sand above. In sinking wells, spots should be selected where the vegetation in the wadis is of a brighter hue, and where heglig and the dom palm exist. In December, 1871, water was found in many such places, never more than 15 feet below the surface. The trap dyke in the vicinity will provide any quantity of fairly bedded stone with which to line the sandy sides of the well ; the way I should suggest, would be, in the first place, to dig through the sand until water be reached, and then to excavate the ground in a circle of say, 24 feet diameter, lining it with a dry stone wall 3 feet in thickness, in this should be built, at intervals, pieces of hard wood, of which there is a large quantity, in order to form a rude ladder ; as soon as the water is reached, a Norton's tube pump should be driven some 6 feet or more ; this will prevent the accumulation of insect life, to be found in any open pools in the vicinity, and prevent other pollution ; then, when this runs dry, the excavation should be again carried down to the lowering water level, and a well of internal diameter of 14 feet be built with a dry stone wall of say, 2 feet thick (the word in India for this form of well is " butcha "), the Norton tube driven down, and the process repeated as the waters lower. Were it possible to procure lime readily, the well might be sunk from the top, as is so habitually done in India, but the only limestone found in the Bayuda is at the plain of El Mesalima, as mentioned above. The stone near these wells, and of which as described above, the supply will be practically unlimited, may be used in constructing defensive works, whilst there will be in their neighbourhood large quantities of fuel, and a considerable amount of bush that will serve as fodder for the camels.

A considerable quantity of sheep, milk, etc., may be procured from the neighbouring tribes. The Jebel Gilif presents a certain source of danger (during the expedition, 1884) : this consists of, in places, an almost precipitous face of some hundreds of feet in height, at the foot is an irregular talus formed by the degradation of the face, and by the stones and boulders brought down the "khors " (ravines) with which it is intersected. These " khora " are, in many places, near their debouchure from the mountains, very narrow (in places only one camel can pass at a time), with steeply precipitous sides, the bottom being of granite rock, polished by the materials carried down in the torrents of the rainy season, and in many places half blocked up with boulders and iWn-ix. As these " khors " rise to the level of the range they widen out into valleys, well supplied with wood, water, forage, etc., where large numbers of men could be kept concealed for a considerable period.

Itcpoii on El Ein.

Situation. El Ein is situated about 130 miles from Debba up the Wadi El Melh. The general trend up the wadi is S.S.W.

At El Ein on the western bank, for some 60 miles northwards and a short distance southwards, is a precipitous escarpment of rugged outline, but extremely uniform in height, known as Jebsl Makakush. El Ein is a gorge in this, the northern promontory of which is surmounted by a rock of curious shape and is called El Serg.

There are two places where water is obtainable along the route from Debba to El Ein, one called Mahtul about 30 miles from Debba has two wells, and the other is Soteir another 30 miles further on. The latter is the better