3 53 9 PROCEEDINGS CF THE GEOLOGICAL SOCIETY. 
The dip varies in different localities, being considerable (32° in the 
valley of Kossier) in the vicinity of the plutonic rocks, but hardly per- 
ceptible on the banks of the Nile. It is usually more inclined on the 
shore of the Red Sea, owing to its greater vicinity to the plutonic 
belt. The direction of dip also varies: in the valley of Kossier, for 
instance, it is to the east and west of the anticlinal ridge, but its 
general direction is decidedly northerly. 
Lithological Character and Economic Uses.—The upper beds of this 
great limestone region abound with nummulites, and differ lithologi- 
cally from the lower, being generally of a hard, compact, waxy tex- 
ture, and of a buff or fawn colour. They are often singularly honey- 
combed, as at Gebel Ataka, as if the substance of the imbedded shells 
had dropped out, or been absorbed by the rock. The limestone is 
often siliceous, and sometimes probably contams magnesia, effer- 
vescing feebly with acids. The lower beds have a cretaceous aspect ; 
but whether the lithological distinction I have attempted to draw will 
be borne out by a more minute examination of the fossil contents of 
the beds remains to be proved. The lower strata are usually white, 
of an earthy chalk-like texture, imbedding nodular and tabular layers 
of chert, as in the vicinity of Thebes and Bir Anglaise. These layers 
range in regular succession from a foot and upwards asunder, The 
nodules are often covered with a white siliceous powder or coating, | 
sometimes containing muriate of soda; and this siliceous powder 
enters largely into the composition of the earthy limestone. Besides 
chert, Egyptian jasper and agate, occasionally replacing the chert, 
these beds contain layers of earthy and crystallized sulphate of lime, 
muriate of soda, cale spar, arragonite, rock crystal, large deposits of 
the beautiful variety of stalagmite called Egyptian alabaster*, and 
stalactitic cavernst+. The lower portions are interstratified with beds 
of faint greenish and light brown marls used in pottery, and for pur- 
poses of washing by both modern and ancient Egyptians. The more 
indurated portions are used as whetstones. Among other minerals, 
sulphate of barytes is said to occur in the limestone near Cairo. 
Lead ore (galena) was found in it at some old mines about thirty miles 
north and about a similar distance to the south of Kossier, in combi- 
nation with silver, by Mr. Burton ; crystallized sulphur, and nodules 
of carbonized vegetable matter, occur in the specimens of limestone 
* The principal quarries of this beautiful mineral, so much used in the manu- 
facture of antique vases, are situated in the eastern desert near Teb el Amara, in 
about 27° 43’ N. lat. The modern quarries lie in the Mokattem, about eight hours’ 
distance from Benisuef. The mineral here presents layers of a faint translucent 
pink or amber colour, alternating curvilinearly with others of a pure opake white 
and of less thickness. The fracture of this mineral is between granular and 
splintery, obscurely conchoidal ; and effervesces with acids. Itis quarried in masses 
large enough for columns of considerable size, and has been lately largely em- 
ployed by the Pacha in lining his baths, for the pillars of the magnificent new 
mosque at Cairo, and the fountain in the great square at Alexandria. 
tT The calc sinter found in the roofs of the caverns, for instance near Mempha- 
lit, affords the whitest alabaster of Egypt. The translucent sarcophagus brought 
by Belzoni to Egypt is composed of arragonite. These caverns, with their stalag- 
mitic bottoms, afford an almost untrodden field for the geologist. It is probable 
they are rich in fossil bones.—Wellsted’s Travels, vol. ii. p. 123. 
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