oases, particularly those of Dakhel and Khargeh, are remarkable for
their fossil wealth. The soil of the deep depressions in which these
oases lie, partly below the level of the Nile, consists of the variegated
clayey or sandy strata of the upper chalk. The ground is so strongly
impregnated with alum at places that it was thought worth while about
thirty years ago to erect manufactories for its preparation, but the un¬
dertaking was afterwards abandoned owing to the difficulties of transport.
Numerous thermal springs well up from the upper strata of the chalk, and
the soil thus irrigated is luxuriantly clothed with vegetation (see p. 64).
The barrier of Nubian sandstone which abuts on the valley of the
Nile at Selseleh extends far into the Libyan desert. It forms the south¬
western boundary of the oases of Khargeh and Dakhel, beyond which it
stretches for an unknown distance into the heart of the desert. This for¬
mation contains silicified wood and iron and manganese ores in abundance.
About six days' journey to the W. of the oases begins a complete
ocean of sand. As far as the eye can reach we discover nothing but
a vast expanse of loose yellow sand, which generally forms itself into
ranges of sand-hills, many miles in length, and occasionally rising to a
height of 300 ft. or upwards above the level of the plain.
The oasis of Farafra lies in a recess eroded in the nummulite lime¬
stone , and enclosed by precipitous slopes, except on the S. side where
there is an opening. To the N. and W. of Farafra extends the eo¬
cene limestone plateau as far as the neighbourhood of Siwa, between
which oasis and Bahriyeh it is remarkable for its numerous basin-shaped
and sharply defined' depressions. These basins, especially those which
are filled with salt-lakes, impart a peculiarly attractive character to the
scenery. The whole of the desert around the Oasis of Ammon consists
of recent tertiary deposits, the fossil wealth of which was once extolled
by Herodotus and Eratosthenes.
Approximately speaking, the Libyan Desert consists of Nubian sand¬
stone , the upper chalk, the nummulite limestone, and the more recent
tertiary formations, arranged in this sequence, and extending in broad
successive strips from S.S.E. to N.N.W.
The Oases (by Prof. P. Ascherson). In the midst of the Libyan De¬
sert, the most bleak and desolate part of the whole of the African Sa¬
hara, at a distance of several days' journey to the W. of the Nile,
there have existed since hoar antiquity a number of highly favoured
spots, which are abundantly irrigated by subterranean supplies of water,
and richly covered with vegetation almost vying in luxuriance with that
of the valley of the Nile. The Coptic word 'Wah', according to Brugsch,
is of ancient Egyptian origin, and signifies an inhabited station; in its
Greek form 'oasis' (properly Ouauic; or Aouji;), the word is used as the
geographical term for irrigated and cultivable spots, or islands of vege¬
tation, in the midst of the stony and sandy ocean of the desert.
Four of the five Egyptian oases lie in a somewhat curved line drawn
from S.E. to N.W., and converging at the S. end to the valley of
the Nile: — (1) Wdh el-Khdrgeh, i.e. 'the outer oasis' (already so named
by Olympiodorus in the 5th cent. A.D.), or Oasis Major of antiquity.
situated 3-4 days journey from Thebes or from Girgeh on the Nile. (2)
Wdh ed-Ddkheliyeh, or more commonly Ddkhel, i.e. the 'inner oasis' (also so
named by Olympiodorus), 3 days' journey to the W. of Khargeh, and about
6 days' journey from the valley of the Nile near Siut. (3) Fardfra (i.e. the
bubbling springs), about 5 days' journey to the N.N.W. of Dakhel, and 8-10
days' journey from the valley of the Nile near Siut. (4) Siwa, anciently
the celebrated oasis of Jupiter Ammon, 16 days' journey to the W.S.W. of
Alexandria and about 14 from Cairo. The direct route from Siwa to
Farafra (traversed by Rohlfs and Zittel in 1874 in 10'/2 days) is little
known as yet, as most European travellers make the long circuit towards
the E. via. — (5) Wdh el-Bahriyeh, i.e. 'the northern oasis', or Oasis
Minor of antiquity, situated 5V2 days' journey to the S.W. of Medinet el-
Fayum, about 4 days' journey from Behneseh in the valley of the Nile,
9 days from Siwa, and 5 days from Farafra.