The third chapter is an account of the surveying methods employed and the principal geographical results obtained. The surveying methods are treated at some length, firstly because an adequate specification of the survey methods used is necessary for the assessment of the value of any contribution to modern geography, and, secondly, because some of the methods are either new or little known, and have been found by experience to be specially adapted to the mapping of this type of country. The principal geographical results are given, mostly in tabular form, as exhibiting clearly the groundwork of the actual maps, and as indicating a series of adequately fixed positions which may be employed as a basis in any further surveys. In the fourth to sixth chapters the drainage lines and hill features are systematically described. A knowledge of the drainage lines, as the key to a precise understanding of the relief, is nowhere more important than in these deserts. In the seventh chapter the important question of water supplies is considered, and the positions and particulars of the various water sources are tabulated for easy reference. The eighth to tenth chapters deal with the various rocks occurring in the district. The petrology of the region has been discussed with some fulness, because while the district offers a remarkable wealth of rock-species, well exposed in considerable masses, detailed studies of Egyptian petrology have hitherto been few. My great regret in this connexion is that I have been unable to add chemical analyses of the rocks. The eleventh chapter summarises the general geological structure and history of the region, as gathered from a broader outlook over the detailed geological evidences. In the twelfth chapter I have set down the information I was able to obtain regarding the territorial limits of the different Bedouin tribes inhabiting the region. The thirteenth and concluding chapter of the book consists of brief notes taken on the return march to Port Sudan.