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a distinctive colour tint can be applied to the erosion surface. This is better restricted to elear examples of a stage and not applied to doubt-ful and little substantiated hypothetical reconstructions.

The techniąues and cartography described above provide the begin-ning of the programme for geomorphological mapping in the arid zonę. Detailed maps of 1 :50,000 are important but as many of the features of the landscape are large scalę the production of maps covering wider areas provides valuable additional data. These maps should of course be based on a knowledge of the detailed landscape but in a country cover-ing nearly 1,000,000 sąuare miles only smali parts can at present be reproduced as detailed maps.

In the present programme of geomorphological mapping in the Sudan it is hoped to map in detail other selected landform types. Besides the work in progress on the Red Sea Coastal plain and the Red Sea hills, and the areas near Khartoum; a morphological map of the same type has been reproduced for part of the Qoz area of Kordofan (by M. Baumer, Animal Resources Dept.) and it is hoped to incorporate some mapping of main morphological units in the recording work of Land Use Officers in the Sudan. In a country in the stage of development of the Sudan the geomorphological map may be an important base map on which to base planning of the futurę development of the area.

Also it seems that the detailed mapping of the semi-arid and arid environments will lead a long way towards solving many of the geomorphological problems in these areas. In some ways these problems appear to be morę straightforward than those of the complicated glacial zones of Europę and are morę amenable to concentrated geomorphological study. Geomorphological maps provide the data for quantitative study of landform development. They thus represent the beginning of the study of the physical history of the region.