The sea coast north of latitude 24° 10′ was adapted from the Admiralty Chart, fitting it on to coast points trigonometrically fixed. South of 24° 10′ the coast was surveyed in detail by means of depression angles from the occupied peaks of the triangulation. The local circumstances, in the existence of high mountains pretty close to the sea, are so favourable to the employment of this method, that it is confidently believed that the maps represent a considerable advance in accuracy over the Admiralty Charts. It was frequently possible to check the accuracy of the coast-line delineation by plane-table rays, and it was invariably found that the errors were insensible, even on the fairly large scale employed in the field-maps. The coast-line shown is the high water-line. The tidal change of level, though it is generally less than a metre, uncovers in many places extensive coral reefs at low water, but no attempt was made to map these. Very special care was taken with place-names, which are transliterated on the Egyptian Government system. It may be remarked that this system is based on the Arabic _spelling_, not on pronunciation. Thus, in this part of the country, the letter _g_ is almost always soft, like an English _j_, and the _q_ is always sounded like a hard _g_. The same system was used for the Bishari and Ababda names, these being first written by a guide in Arabic characters and then transliterated. It is believed that the orthography is correct in almost all cases. The geology was examined along every line of march, and additional specimens were obtained by sending guides to collect rocks from mountains otherwise unvisited. Where possible, the principal geological boundaries were drawn direct on the plane-table sheets in the field, and the remainder have been placed from field notes. The limits of the different igneous and metamorphic rocks shown on the geological map aim only at showing general relationships, for in many cases it is difficult, owing to insensible gradations, to decide exactly where granites and diorites end and gneisses and schists begin, while in other places rocks of two or three distinct species are so intimately mixed that the boundaries could not be shown on the small scale used, even if the exact limits were traced by a life-time’s work; in these latter cases the areas are coloured in accordance with what appeared to be the dominant rock within them. Throughout the three seasons’ work I was accompanied by Dahab Effendi Hassan, who rendered useful assistance in booking angles and in reconnaissance, and in the third season Mr. O. N. Bakewell also accompanied me and gave me much useful help. The Egyptian unskilled staff employed consisted almost entirely of Bedouin and comprised on an average about twenty-five camel drivers (for thiry-five baggage camels), six porters, three guides, and two postmen, all placed under an Arab sheikh.