One of the longest cross-country traverses I myself have undertaken in the Libyan Desert was from Farafra Oasis to Assiut. The only road between that oasis and the Nile Valley strikes the latter near El Qusîya, midway between the towns Manfalut and Derut, so that travellers who wish to make Assiut have an additional day’s march southwards alongside the margin of the cultivated lands. On gaining the summit of the pass above Bir Murr, on the east side of the Farafra depression, I abandoned the road and set a course direct for Assiut, steering and plotting my route by compass and plane-table, the distance being reckoned by measuring-wheel. The most satisfactory method of procedure on desert traverses is to lay out a line, representing the correct bearing of the destination, along the centre of the longer axis of the plane-table, and then to steer to any well-marked object lying on either side, but within reasonable distance, of the proper course. At every station the exact position reached is plotted, and steps are taken, when selecting the next point on which to march, to converge towards the correct course marked down the centre of the table. On this particular traverse I was unaccompanied by Europeans or Bedawin, my camel drivers being fellahin from the Nile Valley. The surface proved excellent going, and the Abu Mohariq belt of dunes, 190 kilometres from Qasr Farafra, was crossed without trouble. Eight days after leaving Farafra village we struck the escarpment of the Nile Valley, having covered nearly 300 kilometres, and found we were marching on a point only very little to one side of the town of Assiut. From this traverse it was possible to calculate the longitude of Farafra with fair accuracy. The normal rate of travelling of camels carrying ordinary loads weighing from three to four hundred-weight is 4 kilometres, or about 2½ miles, an hour, ten hours being the usual day’s march of caravans when accompanied by Europeans. The native caravans, carrying dates and other heavy merchandise, usually traverse the plateau in three days and nights, doing stages of 60 to 70 kilometres at a stretch. By travelling very light with trotting camels I have, on more than one occasion, crossed from the oasis to the valley in between thirty and thirty-five hours, doing from 180 to 190 kilometres in two stages of about twelve hours each, with one stop only of nine or ten hours. CHAPTER IV TOPOGRAPHY AND GEOLOGY Dimensions of the Oasis-Depression — Jebel Têr, Jebel Tarif, and other Hills within the Depression — Aspect of the Oasis from the surrounding Escarpments — Geological Sequence — Nature and Thickness of the Strata — Geological History of the Oasis — Formation of the Depression — Difference of Level of Strata on either side of the Depression — The Great Longitudinal Flexure — Height of the Floor compared with Sea-Level — Altitudes.