— 115 — 
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 through- 
out the country, the main supply being however obtained by evaporation from 
the shore lagoons along the coast of the delta. Pock salt of fine quality occurs 
in many localities, notably in the Eocene limestones three to four days east of 
Assiut. 
