A Technical Discussion of the Mapping of Arenas

Abstract

A study of sub-arid erosion is not only important for the tracing and evaluating of primary stanniferous deposits, but it is also of great practical value for the mapping of these regions. On comparing Prof. Salée’s map with that of the author (map3) and observinghow theNdorwa arena has been mapped, it will be seen that in the writer’s opinion that arena is formed entirely of granite, whereas Salüe indicates only some marginal outcrops of granite. Combe, too, is of opinion that at least the part of Ruanda bordering on Ankole consists of granite, contrary to Salée’s representation (see fig. 17).