The mineralogy of some Nile sediments.

Abstract

Dr. Shukri9s reply to the discussion (pp. 530-4) ::— The author thanks the speakers for their kind remarks and for their interest in the work. He also thanks Dr. Sandford for his answers to the questions raised. He fully agrees with Dr. Sandford that the Blue Nile and Atbara sediments were not added suddenly to the Nile system. Their material appeared for the first time in Lower Palaeolithic terraces and were absent in Pliocene and Plio-Pleistocene sediments. In reference to Dr. Wiseman9s remarks, the author states that local contamination is observed at present along the course of the Nile and is not restricted to the cataracts. Some of the Nile sediments in Egypt, for example, contain Nummulites and other fossils derived from the sedimentary formations north of the first or Aswan cataract. These, and any other material brought from the neighbouring deserts by wind or by casual torrents, are, however,of negligible importance in the recent sediments, as can be seen at present. The mechanical constitution of the sediments was determined and the clay fractions were investigated and the results will be given elsewhere. In reply to Mr. Edmonds, the genetic significance of the uncommon minerals which are liable to spice the assemblages of the commoner minerals was taken into consideration in the paper. Some of these very scarce minerals are recorded as one grain in one slide out of five. On the other hand, the author sees no objection to the use of the more abundant minerals as evidence in