Sandstone is quarried for local purposes at J. Ahmar near Cairo and in several localities in the south part of the country; it was formerly extensively quarried at J. Ahmar for the temples of the Delta, at J. Silsila for those of Upper Egypt, and at Girtassa, south of Assuân, for the Nubian monuments. Although a fairly hard and good weather-resisting stone when carefully selected, the frequent presence of soft uncemented and clayey laminae gives it an unreliable character, and a good deal of the decay of many of the ancient Egyptian monuments is attributable to this cause. Numerous rocks in the Red Sea Hills and the Nile Valley were worked in Egyptian and Roman times for ornamental purposes; among them may be specially mentioned the purple imperial porphyry of J. Dokhan, the green breccia of Wadis Hammamat and Dib, the dolerite of Wadi Esh, and the hornblende granite of the first cataract. In modern times local granite was used throughout the Assuân dam and an Oligocene basalt is quarried at Abu Zabel and used for road-metal in the capital and other towns. Old workings and mining camps are of common occurrence in many parts of the Eastern Desert and there is no doubt that considerable quantities of gold were extracted by convict labour. The quartz lodes traverse not only the metamorphic rocks but also some of the granites. Iron (hematite, limonite), copper (chrysocolla, copper pyrites) and lead (galena) bearing veins also occur, and turquoise, jasper and chrysolite are found in certain localities. Petroleum and sulphur occur sparsely near J. Zeit, and gypsum in large quantities in many parts of the country. Phosphate deposits in the form of accumulations of bones, teeth and coprolites of fish in compact beds, have a wide distribution in the Eastern Desert, the Nile Valley and the southern oases, though these beds have not yet received the attention their importance deserves. Better known are the nitrate bearing clays which are so highly valued and largely used by the fellahin throughout the country. The chief horizons are the Esna shales and the underlying cretaceous clays, but disintegrated clays of every age are worked throughout the country, though their nitrate content may be very low and their salt content high; more prized still is the material from the middens marking the sites of ancient towns. Natron (carbonate of soda) and salt are associated in considerable quantities in Wadi Natrun, and the latter is widely distributed in limited quantities throughout the country, the main supply being however obtained by evaporation from the shore lagoons along the coast of the delta. Rock salt of fine quality occurs in many localities, notably in the Eocene limestones three to four days east of Assiut. APPENDICES TABLES PAGES A. I. Areas of the catchment basins of the Nile 119 B. II. Slopes of the Nile in its different reaches 120