Dr. Bonney having been so kind as to examine microscopically and describe a collection of crystalline rocks which I made in the vicinity of Assouan on the Nile, I have prepared the following notice of the geological conditions, to accompany his descriptions, referring, however, to the notes on the locality given in my paper in the Geological Magazine for Oct. 1884. Reference may also be made to the paper of Lieut. Newbold in the Journal of the Geological Society, vol. iv., and to that of Mr. Hawkshaw in the same journal, vol. xxiii. Lartet has given in his Geology of Palestine a summary of the observations of Russegger, Rivière and Figari Bey on the crystalline rocks of the Nile, and the allied rocks of the Sinaitic Peninsula have been described by him, by Bauerman and by Holland, and more recently by Hull. All these authors have given, more or less distinctly, a series of gneisses and micaceous and hornblendic schists associated with intrusive granites and diorites as the oldest rocks of these districts, and succeeding these in geological age, certain slates and associated rocks, with porphyry and basanite in beds and veins.