— 157 — 
Here they re-appear on the eastern scarp of the oasis, attaining a thickness of 
some 80 metres where the roads to Sohag and Girga ascend the cliflt''. Tliey 
can he followed round the north end of the excavation, hut on hending west- 
ward pass into stratified marls with difificulty distinguishable from the Eocene 
strata above, containing Lucina thehaica. Their nitrate content has been but 
little studied hitherto. The two analyses made by the Survey Department 
Laboratory give as results : 
0/0 0/0 
Sodium Nitrate 11.20 and 1 . 
Sodium Sulpliale 0.00 — 10. 85 
Sodium Chloride 21.00 — 33. 16 
but the record of locality as regards the best analysis was only vaguely given 
by the sender of the sample. 
The Esna Shales are absent in Dakhla Oasis, and the Ash-Grey Shales ap- 
parently not very easily accessible, so that the nitrate possibilities there do 
not seem very encouraging'^'. 
The main strata of this nature probably pass to the northward of the oasis 
scarp, for they reappear finely developed in the hills to east and west of the 
Farafra depression, where they attain a thickness of i5o metres'^'. 
EXTENSION OF NITRATE SHALES 
IN THE EASTERN DESERT. 
We have seen that both in the Oases and in the Nile Valley the nitrate- 
bearing beds fall into three divisions, consisting of two shale series with a 
white limestone between them, the whole underlying typical Eocene marly 
limestones with Lucina thehaica. Tliey reappear with the same characters near 
the Kom Ombo Plain, where these strata have been let down against much 
older beds by an extensive east-west fault. This accounts for the presence of 
the salts recorded in the previous pages as studied by Mr. Hughes. 
The Esna Shales have been traced throughout the Eastern Desert between 
Ball, J., Kharga Oasis. See list of thicknesses on p. 9 A. 
Beadnell, H. J. L. , Dakhla Oasis, p. 81. 
Beadnell, H. J. L. , Farafra Oads , PI. Ill and VIIT, p. 20, etc. 
