786 
and called by the Arabs Nuktah, or drops. These concretions are 
sometimes united in pairs, and often present various modifications of 
a spheroid. Ehrenberg has not been able to detect any traces of 
organic structure in them, but he has noticed fragments of granite 
and other rocks. The lower beds yield also layers of earthy and cry- 
stallized gypsum, chloride of soda, arragonite, large deposits of stalag- 
mite or Egyptian alabaster, near Tel el Amara (lat. 27° 43’) and in 
the Mokattem range, 8 hours from Benisuof; also in caverns fine 
stalactites, used in the arts. Among other mineral products, Mr. 
Newbold mentions sulphate of barytes, lead, crystallized sulphur, and 
nodules of carbonized vegetable matter. Interstratified with these 
lower beds are greenish and pale brown marls, the softer portions of 
which are used in washing, and the harder as whetstones. This lime- 
stone was employed in constructing the earliest Egyptian monuments. 
According to Ehrenberg, the lower beds of this formation contain 
Infusoria and Foraminifere found in the Chalk of Europe ; and to 
Lefevre *, Echinites at Esneh similar to those of Malta, also speci- 
mens of Hippurites, Placuna, and Vulsella, and a fish near Cairo; 
large Nautili, and numerous other testacea, with remains of crabs, 
fishes’ teeth and corallines, were collected by Mr. Newbold. The 
author refers also to Mr. Bowerbank’s observations that the Egyptian 
jaspers present no spongeous structure, but contain numerous Fora- 
miniferze resembling those found in chalk flints, yet difficult to distin- 
guish from species obtained in the calcaire grossiert. 
5. Upper Sandstone.—This formation occurs in horizontally strati- 
fied hummocks and patches resting on the marine limestone ; and it 
has been traced from the Mediterranean far into the Nubian, Li- 
byan and Baytida deserts, and even into Abyssiniat. The hummocks 
- are considered to be the remains of once continuous strata. The 
sandstone varies from a red, white or yellow compact rock to a 
loose quartzoze grit, with a calcareous, felspathic or ferruginous 
cement, and associated with it is a conglomerate composed of quartz, 
chert and jasper, derived chiefly from the subjacent limestone; also 
beds of variously coloured marls containing gypsum and salt, and 
in which the natron beds of Egypt are situated. 
Casts of marine shells were noticed by Mr. Newbold in the vici- 
nity of Wadi Ansari, and trunks with smaller fragments of silicified 
trees occur in many parts of the Egyptian and Libyan deserts, par- 
ticularly in the Suez desert, seven miles east by south from Cairo. 
This district, called the ‘‘ petrified forest,” is described in great de- 
tail. It consists of a sterile irregular plateau, which is considerably 
above the level of the Nile, lying on the slope of the Mokattem range, 
andit extends three and ahalf miles southwardly, and four miles east- 
wardly. Many of the trunks are scattered over the surface among 
rolled and angular fragments of dark grit, and pebbles of jasper, 
chert, quartz and sharp-edged fragments of silicified wood. ‘The 
* Bulletin Soc. Géol. de France, tome x. pp. 144, 234. 
T See ante, p. 435. 
¢ Lefevre, Bull. Soc, Géol. de France, tome x. 
