- 155 — 
upper portion is relatively poor. There are, however, a few localities where 
the upper strata are preferred. It is certain that there is no one bed throughout 
the area which is at the same time rich in Sodium Nitrate, and of any wide 
extent, but that the nitrate occurs unevenly distributed both horizontally and 
vertically throughout the series. In 1906 the present writer visited the expo- 
sures 1 5 kilometres cast of Sibaia, where the Upper or Esna Shales were being 
worked, the lower ones having been exhausted by the fellaliin. Up to that 
date, the company then operating had extracted hooo cubic metres of nitrate. 
The shale average recorded was 8 ojo of useful salts. Shales just recently 
opened yielded 28 0/0 of all salts, occurring in bands four metres thick. They 
contained on an average 5 to 9 ojo of Sodium Chloride, combined with 
nitrates and sulphate of lime. 
The shales are extensively worked in the low hills of the Sharawna neigh- 
bourhood, and are again well developed further north at the foot of the high 
limestone scarp trending northward and eastward from Shaghab. 
The late Mr. Barron reported Gebel Rahamia, 2 5 kilometres north-east of 
Esna, as being especially worthy of mention, the fellahin even coming from 
Luxor to obtain shale at this spot. 
Opposite Gebelain, the deposits are hidden under later limestone gravels, 
but again appear to the south of Luxor at the foot of the clilf. Hidden by the 
later formation for a time, they reappear again as an inlier along a ridge 
h or b miles from the cultivation, where they are capped in places by igneous 
gravels. 
Along the cliff edge from Gebel Uahamia to Mualla, the lower part of the 
upper shales is worked. These attain a thickness of 85 metres, and the best 
material is obtained from 35 to 65 metres below the summit of the shales. 
As regards thickness, the Nitrate Shales which extend northward to a point 
opposite Gebelain and overlie the white limestone, attain a thickness of 1 1 o 
metres, but accurate measurements are difficult to obtain, since their base and 
summit are rarely seen in the same section. 
Nine to ten kilometres east of the village of Khizam, is a bed of reddish 
clay 1 to 1.25 metres thick, which contains a fair amount of Sodium Nitrate 
(see Analyses 1 7 to 19, Table n° 2, p. 1G8) but is much covered with down- 
wash and consequently diflicult to find. 
20. 
