The principles and objects of geology, with special reference to the geology of Egypt

THE PRINCIPLES AND OBJECTS OF GEOLOGY.
MINISTRY OF FINANCE, EGYPT.
SURVEY DEPARTMENT.
By W. F. HUME, D.Sc., F.R.S.E., etc. Director, Geological Survey of Egypt.
Technical Lectures delivered in the Survey Department, Giza, on January 20, and February 10, 1910.
CAIRO: Printed at the National Printing Department, and to be obtained at the Sale-Room, Geological Museum, Ministry of Public Works Gardens; at the Survey Department, Giza (Mudiria); or through any Bookseller
1911.
Price 5 p.t.
THE PRINCIPLES AND OBJECTS OF GEOLOGY WITH SPECIAL REFERENCE TO THE GEOLOGY OF EGYPT.
Similarly, if we were to go southward towards Aswan, a change would be noted in the character and composition of the rocks which form the cliffs bordering the Nile Valley. From Cairo to Qena, limestones predominate; but from thence southward to Esna, clays play a large part at the base of the limestones, and the slipping of the latter over these softer members has given rise to the “tumbled” country which is so conspicuous a feature between Armant and Matana. South of Esna the clays in their turn disappear, while the sandstone which is seen underlying them near Mahamid becomes the dominant constituent of the hills from near Edfu to the neighbourhood of Aswan; at this locality the sandstone itself vanishes, except in so far as it forms isolated caps on the granite, which is the principal rock in the well-known district of the First Cataract.
The same lesson as to the order of succession of the rocks in Egypt is forced home if we move from Qena eastward to the Red Sea hills, or south-westward to Kharga Oasis. East of Qena the clays are a conspicuous feature at the base of the outlying limestone hills (Abu Had, etc.), and in their turn rest on sandstone, which forms striking plateaus seamed by deep ravines giving entry to the heart of the Red Sea hills. On traversing these gorges, a confused hill-country of granite (worn into boulders on the surface), or dark-green schists is entered, on whose summits the sandstone occurs as isolated outliers near the main sandstone mass, but to the east disappears altogether.